View
213
Download
0
Category
Preview:
Citation preview
Why ?
Essential for surgeons (and all physicians) Based upon physiology
Disturbances understood as pathophysiology
To Encourage Thought Not Mechanical Reaction
Most abnormalities are relatively simple, and many
iatrogenic
It’s All About Balance
Gains and Losses Losses
Sensible and Insensible Typical adult, typical day
Skin 600 ml Lungs 400 ml Kidneys 1500 ml Feces 100 ml
Balance can be dramatically impacted by illness and medical care
Fluid Compartments
Total Body Water Relatively constant Depends upon fat content and varies with age
Men 60% (neonate 80%, 70 year old 45%) Women 50%
(mEq/L) Plasma IntracellularNa 140 12K 4 150Ca 5 0.0000001Mg 2 7Cl 103 3
HCO3 24 10Protein 16 40
Electrolytes
Fluid Movement
Is a continuous process Diffusion
Solutes move from high to low concentration Osmosis
Fluid moves from low to high solute concentration. Active Transport
Solutes kept in high concentration compartment Requires ATP
Movement of Water
Osmotic activity Most important factor Determined by concentration of solutes
Plasma (mOsm/L)
2 X Na + Glc + BUN
18 2.8
Third Space
Abnormal shifts of fluid into tissues Not readily exchangeable Etiologies
Tissue trauma Burns Sepsis
Fluid Status
Blood pressure Check for orthostatic changes Physical exam Invasive monitoring
Arterial line CVP PA catheter Foley
Case 1
6 month old boy, born full-term Developed worsening vomiting during the
past week Today he is listless, irritable, not tolerating
oral intake Pulse 145, BP 70/50 Diaper is dry, anterior fontanel depressed
Volume Deficit
Most common surgical disorder Signs and symptoms
CNS: sleepiness, apathy, reflexes, coma GI: anorexia, N/V, ileus CV: orthostatic hypotension, tachycardia with
peripheral pulses Skin: turgor Metabolic: temperature
DehydrationChronic Volume Depletion
Affects all fluid components
Solutes become concentrated
Increased osmolarity
Hct can increase 6-8 pts for 1 L deficit
Patients at risk:
Cannot respond to thirst stimuli
Diabetes insipidus
Treatment: typically low Na fluids
HypovolemiaAcute Volume Depletion
Isotonic fluid loss, from extracellular compartmentDetermine etiology
Hemorrhage, NG, fistulas, aggressive diuretic therapyThird space shifting, burns, crush injuries, ascites
Replace with blood/isotonic fluid» Appropriate monitoring
» Physical Exam» Foley (u/o > 0.5 ml/kg/min)» Hemodynamic monitoring
Treatment – Patient weight is 12 kg
Fluid choice? Replace volume Replace Cl
How to order “Bolus”
Think about rate over time Adequate access important
What would maintenance fluid choice and rate be? 4-2-1 rule
Why not replace K right away?
Acid – Base Balance
Acidosis May result from decreased perfusion i.e.
decreased intravascular volume K will move out of cells
Alkalosis Complex physiologic response to more chronic
volume depletion i.e. vomiting, NG suction, pyloric stenosis, diuretics K will move intracellular
Case 1 When should we operate?
Need to wait until adequately resuscitated Why
Monitor by: Normalized vital signs Good urine output Normalized labs
Case 2
64 year old, had colon resection 5 days ago “doing well” ….until…. Suddenly develops atrial fibrillation with rapid
ventricular response P 120, irregular; BP 115/70; RR 20 Temp 38.7 Confused, anxious
Increased Antidiuretic Hormone (ADH)
Causes Surgical stress (physiologic) Cancers (pancreas, oat cell) CNS (trauma, stroke) Pulmonary (tumors, asthma, COPD) Medications
Anticonvulsants, antineoplastics, antipsychotics, sedatives (morphine)
Hyponatremia – how to classify
Na loss True loss of Na Dilutional (water excess) Inadequate Na intake
Classified by extracellular volume Hyovolemic (hyponatremia)
Diuretics, renal, NG, burns Isotonic (hyponatremia)
Liver failure, heart failure, excessive hypotonic IVF
Hypervolemic (hyponatremia) Glucocorticoid deficiency, hypothyroidism
How much Sodium is Enough???
NS 0.9% = 9 grams Na per liter
0.45 NS = 4.5 grams per liter 125 ml/hour = 3000 ml in 24 hours 3 liters X 4.5 grams Na = 13.5 GRAMS Na!
(If 0.2 NS: 3 liters X 2 grams Na = 6 grams Na)
Case 2 - How to treat
A fib: ACLS protocol Correct electrolytes
Replace Mg and K
Decrease volume, fluid restriction
Case 3
23 year old with jejunostomy Had colon and ileum resected due to injury
Tolerates some oral nutrition, but has high output from jejunostomy (2.5 liters per day), therefore requires TPN
P 118, BP 105/60
Current Problems
Hypovolemia Increased plasma osmolarity
2 X 154 + (213/18) + (28/2.8) = 329.8
Hypernatremia Renal insufficiency Acidosis
Case 3 - Hypovolemia
Fistula output High volumes can rapidly lead to dehydration Electrolyte composition can be difficult to
estimate Can send aliquot to laboratory
May need to be replaced separately from maintenance (TPN) fluids
Hyperglycemia
Hypernatremia
Relatively too little H2O Free water loss (burns, fever, fistulas) Diabetes insipidus (head trauma, surgery,
infections, neoplasm) Dilute urine (Opposite of SIADH)
Osmotic diuresis Nephrogenic DI
Kidney cannot respond to ADH Too much Na, usually iatrogenic
Hypernatremia
[0.6 X wt (kg)] X [Serum Na/140 - 1]
Free water deficit:
Example:Na 154, 60 kg person
(0.6 X 60) X [(154/140) - 1]36 X [1.1 -1]36 X 0.1 = 3.6 Liters
Case 3 – How to Treat
Correct hyperglycemia Replace pre-existing volume deficits Reduce ostomy output if possible What to do with:
Acidosis? Hypokalemia?
154 114 28
3.2 16 2.4
Case 4
58 year old, had a recent kidney transplant Laboratory calls with critical value:
Potassium 5.9
What to do?
Hyperkalemia - Common Causes
Spurious Blood drawn above running IV Underlying disease
Renal failure Rhabdomyolysis
Associated medications Too much K+, ACE inhibitors, beta-blockers,
antibiotics, chemotherapy, NSAIDS, spironolactone
Treatment Mild: dietary restriction, assess medications Moderate: Kayexalate
Do not use sorbitol enema in renal failure patients Severe: dialysis
Potassium and Ph
Normally 98% intracellular
Acidosis Extracellular H+ increases, H+ moves
intracellular, forcing K+ extracellular
Alkalosis Intracellular H+ decreases, K+ moves into cells
(to keep intracellular fluid neutral)
Hyperkalemia - Treatment
Emergency (> 6 mEq/l) Monitor ECG, VS Calcium gluconate IV (arrhythmias) Insulin and glucose IV Kayexalate, Lasix + IVF, dialysis
Mild to Moderate Mild: dietary restriction, assess medications Moderate: Kayexalate
Do not use sorbitol enema in renal failure patients Severe: dialysis
Recommended