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Ultrafiltration during
cardiopulmonary
bypass
Dr Amarja
wwwcardiacanaesthesiain | DrAmarja
Introduction
During CPB patients often develop ndash
Fluid overload
Hemodilution
Electrolyte imbalance
Increased capillary permeability
Shifting of fluid to extravascular spaces
wwwcardiacanaesthesiain | DrAmarja
Introduction (contd)
Ultrafiltration is used to manage
Blood volume
Hemoglobin
Proteins
Certain electrolytes
SIRS
wwwcardiacanaesthesiain | DrAmarja
What is Ultrafiltration
UF is the movement of water across a
membrane as a result of hydrostatic pressure
gradient or transmembrane pressure (TMP)
No dialysate is required on the opposite side of
the membrane
As the water diffuses it creates a solute
concentration gradient across the membrane
also termed as lsquoconvectionrsquo
The fluid removed is lsquoultrafiltratersquo or lsquoplasma
waterrsquo wwwcardiacanaesthesiain | DrAmarja
It is an effective means of blood conservation
It increases the volume of RBCs platelets and
coagulation factors
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
What is dialysis
Dialysis is a process in which blood is separated
from a crystalloid solution or dialysate by a
semipermeable membrane
A solute concentration gradient exist between
blood and dialysate causing the solute transfer
by diffusion from higher to lower concentration
wwwcardiacanaesthesiain | DrAmarja
History
In 1854Thomas Graham a Scottish chemist
presented a paper entitled ldquoOsmotic Forcerdquo
which described the process of separating
substances using a semipermeable membrane
Willem Kolff built an artificial kidney
employing the regenerated cellulose membrane
cellophane termed as Kolff-Brigham kidney
Leonard Skeggs amp Jack Leonards developed flat
or parallel plate dialyzer in 1947
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Introduction
During CPB patients often develop ndash
Fluid overload
Hemodilution
Electrolyte imbalance
Increased capillary permeability
Shifting of fluid to extravascular spaces
wwwcardiacanaesthesiain | DrAmarja
Introduction (contd)
Ultrafiltration is used to manage
Blood volume
Hemoglobin
Proteins
Certain electrolytes
SIRS
wwwcardiacanaesthesiain | DrAmarja
What is Ultrafiltration
UF is the movement of water across a
membrane as a result of hydrostatic pressure
gradient or transmembrane pressure (TMP)
No dialysate is required on the opposite side of
the membrane
As the water diffuses it creates a solute
concentration gradient across the membrane
also termed as lsquoconvectionrsquo
The fluid removed is lsquoultrafiltratersquo or lsquoplasma
waterrsquo wwwcardiacanaesthesiain | DrAmarja
It is an effective means of blood conservation
It increases the volume of RBCs platelets and
coagulation factors
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
What is dialysis
Dialysis is a process in which blood is separated
from a crystalloid solution or dialysate by a
semipermeable membrane
A solute concentration gradient exist between
blood and dialysate causing the solute transfer
by diffusion from higher to lower concentration
wwwcardiacanaesthesiain | DrAmarja
History
In 1854Thomas Graham a Scottish chemist
presented a paper entitled ldquoOsmotic Forcerdquo
which described the process of separating
substances using a semipermeable membrane
Willem Kolff built an artificial kidney
employing the regenerated cellulose membrane
cellophane termed as Kolff-Brigham kidney
Leonard Skeggs amp Jack Leonards developed flat
or parallel plate dialyzer in 1947
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Introduction (contd)
Ultrafiltration is used to manage
Blood volume
Hemoglobin
Proteins
Certain electrolytes
SIRS
wwwcardiacanaesthesiain | DrAmarja
What is Ultrafiltration
UF is the movement of water across a
membrane as a result of hydrostatic pressure
gradient or transmembrane pressure (TMP)
No dialysate is required on the opposite side of
the membrane
As the water diffuses it creates a solute
concentration gradient across the membrane
also termed as lsquoconvectionrsquo
The fluid removed is lsquoultrafiltratersquo or lsquoplasma
waterrsquo wwwcardiacanaesthesiain | DrAmarja
It is an effective means of blood conservation
It increases the volume of RBCs platelets and
coagulation factors
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
What is dialysis
Dialysis is a process in which blood is separated
from a crystalloid solution or dialysate by a
semipermeable membrane
A solute concentration gradient exist between
blood and dialysate causing the solute transfer
by diffusion from higher to lower concentration
wwwcardiacanaesthesiain | DrAmarja
History
In 1854Thomas Graham a Scottish chemist
presented a paper entitled ldquoOsmotic Forcerdquo
which described the process of separating
substances using a semipermeable membrane
Willem Kolff built an artificial kidney
employing the regenerated cellulose membrane
cellophane termed as Kolff-Brigham kidney
Leonard Skeggs amp Jack Leonards developed flat
or parallel plate dialyzer in 1947
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
What is Ultrafiltration
UF is the movement of water across a
membrane as a result of hydrostatic pressure
gradient or transmembrane pressure (TMP)
No dialysate is required on the opposite side of
the membrane
As the water diffuses it creates a solute
concentration gradient across the membrane
also termed as lsquoconvectionrsquo
The fluid removed is lsquoultrafiltratersquo or lsquoplasma
waterrsquo wwwcardiacanaesthesiain | DrAmarja
It is an effective means of blood conservation
It increases the volume of RBCs platelets and
coagulation factors
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
What is dialysis
Dialysis is a process in which blood is separated
from a crystalloid solution or dialysate by a
semipermeable membrane
A solute concentration gradient exist between
blood and dialysate causing the solute transfer
by diffusion from higher to lower concentration
wwwcardiacanaesthesiain | DrAmarja
History
In 1854Thomas Graham a Scottish chemist
presented a paper entitled ldquoOsmotic Forcerdquo
which described the process of separating
substances using a semipermeable membrane
Willem Kolff built an artificial kidney
employing the regenerated cellulose membrane
cellophane termed as Kolff-Brigham kidney
Leonard Skeggs amp Jack Leonards developed flat
or parallel plate dialyzer in 1947
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
It is an effective means of blood conservation
It increases the volume of RBCs platelets and
coagulation factors
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
What is dialysis
Dialysis is a process in which blood is separated
from a crystalloid solution or dialysate by a
semipermeable membrane
A solute concentration gradient exist between
blood and dialysate causing the solute transfer
by diffusion from higher to lower concentration
wwwcardiacanaesthesiain | DrAmarja
History
In 1854Thomas Graham a Scottish chemist
presented a paper entitled ldquoOsmotic Forcerdquo
which described the process of separating
substances using a semipermeable membrane
Willem Kolff built an artificial kidney
employing the regenerated cellulose membrane
cellophane termed as Kolff-Brigham kidney
Leonard Skeggs amp Jack Leonards developed flat
or parallel plate dialyzer in 1947
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
What is dialysis
Dialysis is a process in which blood is separated
from a crystalloid solution or dialysate by a
semipermeable membrane
A solute concentration gradient exist between
blood and dialysate causing the solute transfer
by diffusion from higher to lower concentration
wwwcardiacanaesthesiain | DrAmarja
History
In 1854Thomas Graham a Scottish chemist
presented a paper entitled ldquoOsmotic Forcerdquo
which described the process of separating
substances using a semipermeable membrane
Willem Kolff built an artificial kidney
employing the regenerated cellulose membrane
cellophane termed as Kolff-Brigham kidney
Leonard Skeggs amp Jack Leonards developed flat
or parallel plate dialyzer in 1947
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
What is dialysis
Dialysis is a process in which blood is separated
from a crystalloid solution or dialysate by a
semipermeable membrane
A solute concentration gradient exist between
blood and dialysate causing the solute transfer
by diffusion from higher to lower concentration
wwwcardiacanaesthesiain | DrAmarja
History
In 1854Thomas Graham a Scottish chemist
presented a paper entitled ldquoOsmotic Forcerdquo
which described the process of separating
substances using a semipermeable membrane
Willem Kolff built an artificial kidney
employing the regenerated cellulose membrane
cellophane termed as Kolff-Brigham kidney
Leonard Skeggs amp Jack Leonards developed flat
or parallel plate dialyzer in 1947
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
History
In 1854Thomas Graham a Scottish chemist
presented a paper entitled ldquoOsmotic Forcerdquo
which described the process of separating
substances using a semipermeable membrane
Willem Kolff built an artificial kidney
employing the regenerated cellulose membrane
cellophane termed as Kolff-Brigham kidney
Leonard Skeggs amp Jack Leonards developed flat
or parallel plate dialyzer in 1947
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Mechanism of UF
During UF blood passes through a bundle of
hollow fibres made of microporous membrane
The hollow fibres are of 180-200 microm in diameter
and pores of 5-10 nm
The bundle of this hollow fibres is encased in a
polycarbonate shell
As blood passes this hollow fibres of
ultrafiltrator ( also called as hemoconcentrator )
a positive pressure is created This pressure
difference between the blood side and the wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
atmosphere on the ultrafiltrate side drives water
across the membrane
By convection solutes smaller than pore size
move with the water to equalize the solute
concentration gradient
The pressure gradient between the blood and the
ultrafiltrate is called the transmembrane pressure
( TMP ) This is expressed as the formula ndash
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Mechanism ( contd )
TMP = ( P in + P out ) 2 + V
TMP = transmembrane gradient
P in = blood inlet pressure
P out = blood outlet pressure
V = negative pressure applied on the
effluent side of the hemoconcentrator
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Mechanism (contd )
TMP should not exceed 500 -600 mmHg to
avoid rupture of membrane
Rate of UF depends on ndash
Membrane permeability
Blood flow
TMP
Hematocrit
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Membrane permeability is related to ndash
Pore size
Membrane material
Membrane thickness
And is described by ultrafiltration coefficient
Kuf
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Ultrafiltration coefficient
Kuf is the rate of water removal to the TMP for
a particular device at a constant blood flow
Typical rates are 2-50 mLhrmmHg
Increase in TMP increase the rate of UF
Kuf also depends on blood flow so higher the
blood flow results in higher Kuf
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
As the UF removes the plasma water and
diffusible solutes in equal concentrations the
overall concentration of diffusible solutes is not
affected
Depending on the membrane material and the
pore size solutes gt 65000 d are not removed
Celullar elements plasma proteins amp protein
bound solutes are not removed therefore get
concentrated
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Sieving Coefficient
The ability of the solute to filter depends on
molecular weight of the solute compared with
the pore size proportion of the solute that is
membrane bound and the surface charge of the
solute
The lsquosieving coefficientrsquo is the ratio of
ultrafiltrate solute concentration to plasma
solute concentration
It ranges from 0 ndash 1 When it is 1 it indicates
that the ultrafiltrate solute concentration and wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
the plasma solute concentration are equal and that
the solute passes freely across the membrane
And the value of 0 indicates that none of the
solute passes through the membrane
All small MW solutes that are not protein bound
are easily removed by UF and have a seiving
coefficient of 1
Generallysolutes gt50000 daltons do not pass
through the membrane pores ( Albumin has a
molecular mass of 65000 daltons )wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Indications
Pts undergoing CPB have significant hemodilution
due to -
Circuit prime
Through cardioplegia line
Surgical irrigation from cardiotomy suction
Patients may have CCF renal failure
UF removes this excess fluid however the
amount of fluid removed is limited by the
minimal level in the venous reservoirwwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Also the SIRS increases the capillary
permeability causing a dilutional decline in
hemoglobin and serum protein concentrations
The capillary leak causes fluid shifts to the
interstitial spaces causing tissue edema and
decreased end organ function
UF can concentrate blood without removal of
plasma proteins thus causing
hemoconcentration reduction in tissue edema amp
removal of inflammatory mediatorswwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
UF helps by helliphellip
Decreasing the TBW ( total body water )
Decreased postop blood loss
Decreased usage of blood products
Improves LV systolic function
Improves A-a O2 gradient
Increase pulmonary compliance
Decrease duration of postop ventilation
Decreased incidence of pleural effusion after
superior cavopulmonary connections Fontan wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF
Hemoconcentration without removal of protein
segment of blood thus maintaining albumin amp
clotting factors
The concentration of albumin increases the
colloid oncotic pressure and reduces edema by
drawing blood out of extravascular space
In pts with renal impairment its concomitant
use with dialysis can optimize electrolytes and
blood urea nitrogen
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Advantages of UF (contd)
The pulmonary compliance is increased amp there
occurs faster recovery of pulmonary function is
mainly because of leukocyte stability and
decreased degranulation of polymorphonuclear
neutrophils in the pulmonary capillaries
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Ann Thorac Surg 1997 Aug64(2)521-5
Modified ultrafiltration after
cardiopulmonary bypass in pediatric cardiac
surgery
Draaisma AM concluded that Modified
ultrafiltration decreases blood transfusion
requirements and chest drain loss after pediatric
cardiac surgical procedures
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Factors that influence UFhellip
Type of UF
Type of MUF- arteriovenous venovenous
Duration of UF
Volume of ultrafiltrate obtained
End-point chosen for termination of MUF
Type of filter
Use of PUF
Concomitant anti-inflammatory therapies like
steroids wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Patient characteristics ( young age presence of
PAH )
CPB variables like prime volume type of prime
Complexity of surgery ndash use of DHCA
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Risks with UF
Plasma levels of heparin may increase The
heterogeneous molecular size of heparin varies
the amount of heparin retained in the
hemoconcentrated blood
Aortic cannula may entrain air
Hemodynamic instability
High flow rates through ultrafilter decrease the
CBF velocities amp cerebral mixed venous O2
saturation
MUF increases the CPB time wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Contraindications for UF
Biocompatibility
Leukopenia
Complement activation
RBC trauma amp release of plasma free Hg
Retention of heparin in hemoconcentrated
blood
Cost analysis
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Technical Applications
The ultrafiltrator is set in parallel to the extracorporeal circuit as
a passive shunt from a point of higher pressure to lower
pressure The inflow to the ultrafiltrator originates from a
connection off the high-pressure arterial line and the outflow
returns to a lower pressure connection located on the venous
line or the venous reservoir
Without the pump the flow through the ultrafiltrator is
dependent on the pressure differential between the inflow and
outflow of the ultrafiltrator During CPB the perfusionist
monitors line pressure distal to the arterial pump which ranges
between 150 mm Hg and 250 mm Hg and is dependent on
blood flow rate and resistance The resistance to flow is
determined by arterial cannula size design and placement as
well as the patients arterial blood pressurewwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
Tubing from the effluent side of the ultrafiltrator is
attached to a collection canister and given that
ultrafiltrators used for CPB have relatively high
ultrafiltration rates (also termed high flux) sufficient
rates of fluid removal are achieved by establishing a
hydrostatic pressure gradient by altering the height
between the ultrafiltrator and the canister
The hydrostatic gradient can vary between 60 - 90
mmHg resulting in an effective hydrostatic pressure of
approximately 45 - 65 mm Hg The TMP may be
augmented by applying a vacuum source to the effluent
side of the ultrafiltratorwwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Technical Applications (contd)
The process of ultrafiltration may potentially
lead to hypovolemia with increased osmolarity
in the intravascular volume causing interstitial
fluid to slowly shift into the vascular space
A patient supported on CPB can tolerate a
higher rate of ultrafiltration without becoming
hemodynamically unstable because the cardiac
output is controlled by the bypass pump and
does not depend on the intravascular volume
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Types of UF
Conventional UF
Modified UF
Dilutional UF
Zero ndash balanced UF
Prime UF
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Priming of the ECC with non-hemic solutions
results in hemodilution that ranges from 33 to
200 of the ptrsquos volume
After cardiac surgery the extravascular fluid load
may increse greater than 13rd of the adult ptrsquos
prebypass volume
In paediatric perfusion the volume of
hemodilution may far exceed the preoperative
blood volume
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Prime UF
Banked PRBCs are used to perform PUF
It lowers the plasma concentrations of
bradykinin amp HMW kininogen
Less tissue edema
Improved cardiorespiratory status
Reduced duration of mechanical ventilation amp
ICU stay
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
MUF
In 1991 Naik Knight and Elliot et al described
a procedure following termination of CPB the
residual contents of the ECC were ultrafiltrated
and tranfused back while the pts were still
cannulated
This was then called modified ultrafiltration
In MUF nearly all the contents of the circuit are
concentrated and transfused back decreasing the
risk of hypervolumia while the circuit remains
primed with the crystalloid solutionwwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
MUF circuit
Arterial linehelliparterial filterhelliproller pumphellip
hellipcardioplegia device BCD ultrafilterhelliphellip
helliphellipvenous line
MUF circulation ndash from patient to patient
MUF is continued until the hematocrit value is
40 or no blood remains in the bypass circuit
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
At the termination of CPB MUF requires a separate
roller pump to transfer blood from the patient through
the arterial line to an ultrafiltrator and back into the
patient through the venous line As the patients blood
volume is concentrated the arterial pump is used to
transfuse blood from the circuit
Once the venous reservoir is emptied crystalloid
solution is added to the reservoir While the circuit
blood continues to be transfused to the patient it is
displaced by the crystalloid solution until all the residual
blood is transfused to the patient and the circuit is left
primed with crystalloidwwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Pumping the blood from the patient using the
cardioplegia pump which is already connected
to the arterial side of the extracorporeal circuit
The cardioplegia system works well because it
contains a heat exchanger to avoid cooling the
patient pressure monitoring a bubble trap and
a cardioplegia infusion line that is easily attached
to the venous line
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Some have also advocated venous to venous
MUF in which blood is withdrawn from the
right atrium and returned to the right atrium No
direct comparisons of the effectiveness of
arteriovenous MUF and venovenous MUF have
been performed
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
Because the blood is being aspirated from the arterial cannula
with the use of a pump there is a risk of air being entrained from
the arterial cannulation purse strings Once MUF is initiated the
arterial cannula must be checked for air particularly if the blood
flow through the arterial cannula changes from retrograde to
antegrade flow This would occur if CPB has to be reinstituted
or if the infusion rate of the circuit blood exceeds the flow rate
of the MUF pump The pressure in the circuit must be
monitored to avoid any negative pressure occurring in the circuit
which would draw air across the pores of a microporous
membrane oxygenator Negative pressure would result if the
arterial line were to be kinked or clamped
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Risk in doing MUF
To increase the efficiency of MUF high blood flows
have been used to pull blood from the arterial line This
raises concerns regarding the increased aortic diastolic
runoff and the potential for intracranial steal
Rodriguez et al studied the effect of MUF blood flow
rates on cerebral blood velocities and cerebral mixed
venous oxygen saturations during various MUF blood
flows in a group of pediatric patients They found that
MUF blood-flow rates resulted in a decrease in cerebral
blood-flow velocities and cerebral mixed venous
oxygen saturationswwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Paediatric Patients
MUF seems to be most effective in paediatric
patients probably due to the large prime volume
relative to the patients blood volume and use of
deep hypothermia in paediatric cardiac surgery
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Advantages with MUF
The results associated with MUF are very encouraging ndash
Reduction in post-op morbidity
Reduced blood loss and blood usage
Reduced inflammatory mediators
Improvement in myocardial function amp in cerebral
oxygenation
During MUF there is increase in MAP related to
changes in SVR associated with increased blood
viscosity amp via removal of vasoactive substances
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
MUF and HEART
MUF was more effective in preventing
accumulation of TBW and myocardial edema
It also resulted in a significant improvement in
left ventricular contractility assessed by the
preload recruitable stroke work index
The effect of MUF on LV systolic function
using load-independent measures of myocardial
performance changes in left ventricular systolic
function were shown to correlate positively with
the degree of hemoconcentration wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
MUF over CUF
The concentration of inflammatory mediators in
the filtrate does not differ between CUF and
MUF However because the volume of filtrate
removed is significantly greater with MUF
removal of mediators is correspondingly more
Thus whether the mechanism is reduction in
TBW or removal of inflammatory mediators
MUF is more effective then CUF because a
greater volume of filtrate can be removed
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
MUF (contd)
Disavantage of MUF -
Patient remains cannulated for more 10-20 min
Protamine administration has to be withheld
Criteria chosen for termination of MUF -
MUF can be continued until the circuit
contents were completely salvaged use a time-
based criterion use a hematocrit end point or a
filtrate-volume end pointwwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Studieshelliphellip
Effects of CPB and Use of Modified Ultrafiltration by
Ross M (Ann Thorac Surg 199865S35ndash9)
Modified ultrafiltration in pediatric CPB reduces total
body water and serum levels of inflammatory
mediators It results in an elevated hematocrit without
the need for transfusion improved pulmonary
compliance in the immediate postbypass period and
probably improved cerebral metabolic recovery after
DHCA
Conclusions MUF can be performed safely in neonatal
patients after CPB and offers advantages in comparison
with CUFwwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 2001122209-211
copy 2001 The American Association for Thoracic
Surgery
Editorials
Use of ultrafiltration during and after
cardiopulmonary bypass in children
J William Gaynor MD
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
Thompson and colleagues report results of a study
comparing outcomes after CUF and MUF when a
standardized volume of fluid is removed The stated
goal of the study was to determine whether MUF has
any intrinsic benefit over CUF aside from the
potentially greater volume of fluid removed The
volume of filtrate removed was arbitrarily set at 50 to
60 of the effective fluid balance defined as the
priming volume plus volume added during CPB less
the urine output
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Despite the standardization of CPB CUF patients received a
significantly larger priming volume and a larger volume was
added during CPB The reasons for the increased priming
volume are unclear however it is likely that more volume was
added during CPB to maintain the reservoir level during CUF
Because of this additional volume a significantly greater volume
of filtrate was removed during CUF than during MUF
There was no difference in outcome between the 2 groupsThe
study design suggests a misunderstanding of the rationale for
MUF MUF was introduced to allow safe removal of a
greater volume of fluid than possible during CUF and thus more
effectively prevent accumulation of TBW not because any
special efficacy of ultrafiltration performed after separation from
CPB wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
The composition of the filtrate remains the same
whether ultrafiltration is performed during rewarming
or a few minutes later after separation from CPB
Indeed one of the authors of this study stated in a
recent editorial that modified ultrafiltration filters
the CPB perfusate in exactly the same way as
conventional ultrafiltration except the filtration process
is performed after separation from cardiopulmonary
bypass
The beneficial effects of MUF compared with CUF are
dependent on more aggressive fluid removalwwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
ZERO-BALANCED UF
Because most cytokine and complement levels reach their peak
during rewarming continuous UF during this period would
further attenuate the inflammatory response
To allow continuous UF during the rewarming phase replace
the ultrafiltrate with a balanced electrolyte solution
The ultrafiltration rate is matched with the infusion rate by
loading the ultrafiltration effluent line and the electrolyte
solution infusion tubing into a single roller pump The effluent
and infusion tubing are loaded in opposite directions so that the
ultrafiltration rate was equal to the infusion rate and the patient
remained isovolemic wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
Z-BUF has also been used to correct hyperkalemia
Potassium loads originate from hyperkalemic
cardioplegia and homologous red blood cells and may
exceed the patients ability to clear excess potassium
through normal glomerular filtration
As the patients blood volume is reduced by
ultrafiltration the potassium level is not affected
because the ultrafiltrate potassium levels will always be
in equal concentration to the plasma
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Z-BUF (contd)
When the purpose of Z-BUF is to remove
inflammatory mediators the replacement fluid
such as Hartmans solution lactated Ringers can
be used
When using Z-BUF to reduce potassium levels
the previously mentioned replacement solutions
do not efficiently dilute potassium levels hence
09 sodium chloride is often used
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Studieshellip
J Thorac Cardiovasc Surg 20061321291-1298
Modified and conventional ultrafiltration
during pediatric cardiac surgery Clinical
outcomes compared
This prospective randomized study of 60
infants found no difference in clinical outcome
between patients who received DCUF only
patients who received MUF only and patients
who received both DCUF and MUF
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
UF amp Hemodialysis in ECMO
Critically ill patients undergoing long-term
ECMO often present with fluid overload due to
renal insufficiency or failure
Because the circuit is closed in ECMO and the
patient is only on partial bypass they are still
dependent on their native cardiac output If too
much fluid is removed from the vascular space
the patient may become hypovolemic causing
the ECMO flow as well as the patients native
cardiac output to decreasewwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
SIRS with the Use of a
Semipermeable Membrane
SIRS is triggered owing to contact with the
artificial surfaces of the CPB circuit ischemia-
reperfusion injury and operative trauma
The older cellulose and modified cellulose
hemodialysis and ultrafiltration membrane
materials have been shown to increase
inflammatory mediators and initiate complement
activation The newer synthetic membrane
materials such as polysulphone invoke minimal
complement activationwwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
Thank you
wwwcardiacanaesthesiain | DrAmarja
![정밀여과 (Micro Filtration)chungam.co.kr/eng/upload/정밀여과.pdf · [첨부Filter Housing 종류] 1.여과의종류 1).Micro filtration (정밀,미세여과) 2).Ultrafiltration](https://img.pdfslide.tips/doc/110x75/5e58cf0d8346104bfa524381/ee-micro-filtration-eepdf-efilter-housing-e.jpg)
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