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The complications of AV access for H/D
©2007 UpToDate ® The 2006 NKF/Dialysis Outcomes Quality Initiative (K/DOQI) guidelines
The 2006 Canadian Society of Nephrology hemodialysis guidelines
2007-04-09Ri 陳昱潤
Chronic hemodialysis vascular access: Types and placement
1. AV fistulas 2. Synthetic grafts 3. Tunneled cuffed catheters
AV fistulas End-to-side vein-to-artery anastomo
sis The 2005 Canadian and 2006 United
States K/DOQI guidelines: 1. radiocephalic 2. brachiocephalic 3. brachiobasilic 4. Brachial artery and median antecubital
vein
Synthetic grafts Polytetrafluoroethylene (PTFE, also known as Gort
ex) Straight or looped and ranges between 4 to 8 mm i
n diameter Straight forearm (radial artery to cephalic vein) Looped forearm (brachial artery to cephalic vein) Straight upper arm (brachial artery to axillary vein) Looped upper arm (axillary artery to axillary vein) The 2006 K/DOQI work group prefers a forearm loo
p graft
Tunneled cuffed catheters
Internal jugular vein Right sided catheters malfunction
less than left sided Subclavian catheters should be
avoided to prevent subclavian stenosis
COMPARISON Primary failure:
an access that never provided reliable hemodialysis fistula > graft
Secondary failure: graft > fistula
Time to use: fistula: weeks to 6 months graft: days to weeks catheter: intermediate-duration
Recommendation: fistula preferred
Nonthrombotic complications Infection Heart failure Distal ischemia Aneurysm and pseudoaneurysm Venous hypertension Median nerve injury Seroma formation
Infection Accounts for 20% of access loss The source of most bacteremia in H/D p’t S. aureus, S. epidermidis Predisposing factors:
pseudoaneurysms or perifistular hematomas severe pruritus over needle sites intravenous drug abuse secondary surgical procedures
Prophylaxis? unsuccessful in preventing
The 2006 NKF/Dialysis Outcomes Quality Initiative (K/DOQI) guidelines: six weeks Abx for fistula surgical excision with septic emboli infected PTFE grafts:
surgical intervention, may require skin flaps, 3 weeks of Abx
Heart failure Rare, even in p’t with cardiac disease Fistula increase LV hypertrophy High-output heart failure if fistula flow
>20% C.O Treatment:
limiting fistula flow by banding access thrombosis, may not permanently
decrease flow peritoneal dialysis or cuffed catheter
Distal ischemia Distal hypoperfusion of the extremity Shunting ("steal") of arterial blood flow 1-20%, DM and the elderly Absent pulse or a cold extremity warrant im
mediate surgery Paresthesia, sense of coolness with retaine
d pulses, improve over weeks Management:
percutaneous transluminal balloon angioplasty distal revascularization with interval ligation
Aneurysm and pseudoaneurysm
Infrequent complications Repeated cannulation in the same area Pseudoaneurysm:
a particular problem with PTFE grafts, the material deteriorates after prolonged use
If small defect (<5 mm), occlude it! Options for the evaluation: graft rupture
spontaneous bleeding, rapid expansion in size, severe degeneration in the material
The K/DOQI guidelines for intervention: The skin overlying the fistula is compromised a risk of fistula rupture Available puncture sites are limited
Venous hypertension Valvular incompetence or central venous stenosis S/S:
severe upper limb edema skin discoloration access dysfunction peripheral ischemia with resultant fingertip ulceration
Venous duplex ultrasound, venography Treatment:
correcting the underlying vascular problem screening
Median nerve injury
Carpal tunnel syndrome Local amyloid deposition Compression of the median nerve
due to the extravasation of blood or fluid Ischemic injury by a vascular steal effe
ct
Seroma formation Weeping syndrome:
ultrafiltration of plasma across a PTFE graft A pocket of serous fluid, firm and gelatinous Typically at the arterial end of the graft whe
re intraluminal pressure is higher Occur at the distal end if there is significant
central venous obstruction Fistulogram to exclude central venous sten
osis
Thrombotic complications
Introduction The most common (80-85%) complication of permanent vasc
ular access The cumulative fistula patency rate in most centers:
60 to 70% at one year 50 to 60% at two years
Expensive to maintain fistula patency, 15% of annual spending
Predisposing factor: anatomic venous stenosis, 80-85% arterial stenosis excessive post-dialysis fistula compression hypotension increased hematocrit levels hypovolemia hypercoagulable states
A standard definition for stenosis does not exist Narrowing >= 50%
Pathogenesis Initiated by endothelial cell injury Up-regulation of adhesion molecules on the endot
helial cell surface leukocyte adherence to damaged and activated en
dothelium causes the release of chemotactic and mitogenic factors for vascular smooth muscle cells
Enhancing smooth muscle cell migration and proliferation
Activated PLT and inflammatory cells: secrete oxidants and toxins, injure the vessel wall
PROSPECTIVE MONITORINGK/DOQI guidelines for surveillance of grafts :
Intra-access flow: duplex and variable flow Doppler ultrasound magnetic resonance angiography dilution based upon ultrasound, urea, or therm
al techniques Static venous pressure Duplex ultrasonography Gadolinium-based MRI should be avoided d
ue to nephrogenic systemic fibrosis
PROSPECTIVE MONITORINGK/DOQI guidelines for surveillance of fistulas :
Direct flow measurements Physical findings suggestive of stenosis:
arm swelling prolonged bleeding after needle withdraw
al collateral veins altered features of the pulse or thrill
Duplex ultrasonography Static pressure
When to refer? More than one abnormalities Persistent abnormalities Access flow rate <600 mL/min for fistula Access flow rate <400-500 mL/min for graft Venous segment static pressure ratio >0.5 Arterial segment static pressure ratio >0.75
Treatment of venous stenosis
Percutaneous angioplasty Endovascular metallic stents Surgical revision
Percutaneous angioplasty Corrects over 80% of stenosis
in both native fistulas and synthetic grafts in both venous and arterial outflow tracts
The 2006 K/DOQI guidelines recommend angioplasty if: stenosis in fistula >50% stenosis in graft >50% + (abnormal physical find
ings, intragraft blood flow <600, or elevated static pressure)
Success with angioplasty varies with the size of the stenosis
Monitoring: high recurrence rate (55 to 70% at 12
months) Recurrent lesions: repeat angioplasty Summary:
Reduced vascular morbidity Preserves future access sites
Endovascular metallic stents Advocated as a method of
preventing recurrent stenosis after angioplasty
Variable results
Surgical revision
The gold standard The lowest recurrence rate Generally been replaced by
angioplasty: requiring hospitalization extending the fistula site further up
the involved extremity
STRATEGIES TO PREVENT THROMBOSIS
Antiplatelet agents Systemic anticoagulation Antiphospholipid antibodies Fish oil Other preventive therapies
Antiplatelet agents Dipyridamole, low-dose aspirin w/ or w/o s
ulfinpyrazone, aspirin + clopidogrel Neither therapy appeared to be effective, th
e recurrence rate was 78% In patients with new grafts, the rate of thro
mbosis was reduced by dipyridamole (relative risk 0.35 versus placebo).
A surprising finding: apparent increase in thrombosis with aspirin one possibility: cyclooxygenase inhibition shifts
arachidonate metabolism toward nonprostaglandin metabolites (such as lipoxygenases), promote intimal hyperplasia
The role of anti-PLT agents in preventing fistula thrombosis is unresolved
Systemic anticoagulation A paucity of data exists A multicenter prospective study:
warfarin to patients with newly placed PTFE grafts
no increasing graft survival with significant bleeding
We only administer warfarin to p’t with repetitive thrombus but w/o anatomic stenosis
Antiphospholipid antibodies Lupus anticoagulant and anticardiolipin an
tibodies Increased incidence of thromboses Increase the risk of access thrombosis
A report of 97 patients on hemodialysis 62% versus 26%
Reasonable to screen: Warfarin is indicated in patients with
thromboses not involving the access
Fish oil
Omega-3 fatty acids Inhibit cyclooxygenase, may dampen i
ntimal hyperplasia in vein grafts Among 24 patients with PTFE grafts:
At 12 months, the primary patency rate was significantly higher: 77% versus 15%
Other preventive therapies Endovascular radiation
prevention of vascular access stenosis gamma radiation: effective in animal models in inhibiting
intimal hyperplasia catheter-based irradiation: utilized to prevent restenosis
after angioplasty in the coronary circulation primary patency at 6 months was better: 42% versus 0 no difference in secondary patency at 6 (92% versus 91%)
or 12 months (44% versus 57%). Gene therapy
theoretically effective, result in less systemic toxicity
TREATMENT OF THROMBOSESThe 2006 K/DOQI guidelines
With grafts and associated stenosis: Surgical thrombectomy Thrombolysis Mechanical disruption
With fistulas: no recommend any approach to the rem
oval of thromboses
Surgical thrombectomy Outpatient procedure
quick very low complication rate initially success in 90%
However, failure to correct the underlying outflow stenosis leads to rapid rethrombosis
Thrombolysis Attempts to fistula thrombosis with urokina
se and streptokinase, originally yielded disappointing results
Dosing adjustments and technical advances: improved the success rate reduced the incidence of bleeding
Combines thrombolytic therapy with mechanical clot disruption: 90% patency 50% patency in 1 year
Mechanical disruption
A study showed: Similar rate of success with surgical thro
mbectomy and urokinase considerably greater long-term patency
The major concern: pulmonary emboli only 1 of 650 had pulmonary embolus 2 of 650 developed transient chest pain of
undetermined etiology
K/DOQI goals for treatment A success rate of 85%:
defined by the ability to use the graft at least once post-procedure
After percutaneous thrombectomy 40% patency at 3 months
After surgical thrombectomy 50% patency at 6 months 40% patency at 12 months
Summary Nonthrombotic complications:
Infection: 20% Heart failure Distal ischemia Aneurysm and pseudoaneurysm Venous hypertension Median nerve injury Seroma formation
Thrombotic complication: 80-85%
Thanks for your attention!!
References:2007 UpToDate
The 2006 NKF/Dialysis Outcomes Quality Initiative (K/DOQI) guidelines
The 2006 Canadian Society of Nephrology hemodialysis guidelines