The complications of AV access for H/D2007 UpToDate The 2006 NKF/Dialysis Outcomes Quality Initiative (K/DOQI) guidelinesThe 2006 Canadian Society of Nephrology hemodialysis guidelines

2007-04-09Ri

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Chronic hemodialysis vascular access: Types and placementAV fistulas Synthetic grafts Tunneled cuffed catheters

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AV fistulasEnd-to-side vein-to-artery anastomosisThe 2005 Canadian and 2006 United States K/DOQI guidelines:

radiocephalic brachiocephalic brachiobasilic Brachial artery and median antecubital vein

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Synthetic graftsPolytetrafluoroethylene (PTFE, also known as Gortex) Straight or looped and ranges between 4 to 8 mm in 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 loop graft

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Tunneled cuffed catheters Internal jugular vein Right sided catheters malfunction less than left sided Subclavian catheters should be avoided to prevent subclavian stenosis

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COMPARISON Primary failure:an access that never provided reliable hemodialysis fistula > graftSecondary failure: graft > fistulaTime to use:fistula: weeks to 6 months graft: days to weekscatheter: intermediate-duration Recommendation: fistula preferred

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Nonthrombotic complicationsInfectionHeart failureDistal ischemiaAneurysm and pseudoaneurysmVenous hypertensionMedian nerve injurySeroma formation

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InfectionAccounts for 20% of access loss The source of most bacteremia in H/D ptS. aureus, S. epidermidis Predisposing factors:pseudoaneurysms or perifistular hematomas severe pruritus over needle sites intravenous drug abuse secondary surgical procedures

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Prophylaxis?unsuccessful in preventing The 2006 NKF/Dialysis Outcomes Quality Initiative (K/DOQI) guidelines:six weeks Abx for fistulasurgical excision with septic emboli infected PTFE grafts: surgical intervention, may require skin flaps, 3 weeks of Abx

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Heart failureRare, even in pt with cardiac disease Fistula increase LV hypertrophyHigh-output heart failure if fistula flow >20% C.OTreatment:limiting fistula flow by banding access thrombosis, may not permanently decrease flow peritoneal dialysis or cuffed catheter

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Distal ischemiaDistal hypoperfusion of the extremityShunting ("steal") of arterial blood flow 1-20%, DM and the elderlyAbsent pulse or a cold extremity warrant immediate surgeryParesthesia, sense of coolness with retained pulses, improve over weeks Management:percutaneous transluminal balloon angioplasty distal revascularization with interval ligation

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Aneurysm and pseudoaneurysmInfrequent complicationsRepeated cannulation in the same area Pseudoaneurysm: a particular problem with PTFE grafts, the material deteriorates after prolonged use If small defect (

Venous hypertensionValvular incompetence or central venous stenosisS/S:severe upper limb edemaskin discolorationaccess dysfunctionperipheral ischemia with resultant fingertip ulceration Venous duplex ultrasound, venography Treatment: correcting the underlying vascular problemscreening

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Median nerve injuryCarpal tunnel syndrome Local amyloid depositionCompression of the median nervedue to the extravasation of blood or fluid Ischemic injury by a vascular steal effect

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Seroma formationWeeping syndrome:ultrafiltration of plasma across a PTFE graftA pocket of serous fluid, firm and gelatinous Typically at the arterial end of the graft where intraluminal pressure is higherOccur at the distal end if there is significant central venous obstructionFistulogram to exclude central venous stenosis

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Thrombotic complications

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IntroductionThe most common (80-85%) complication of permanent vascular 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 spendingPredisposing factor: anatomic venous stenosis, 80-85%arterial stenosisexcessive post-dialysis fistula compressionhypotensionincreased hematocrit levelshypovolemiahypercoagulable states A standard definition for stenosis does not existNarrowing >= 50%

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Pathogenesis Initiated by endothelial cell injury Up-regulation of adhesion molecules on the endothelial cell surfaceleukocyte adherence to damaged and activated endothelium 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

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PROSPECTIVE MONITORINGK/DOQI guidelines for surveillance of grafts :Intra-access flow:duplex and variable flow Doppler ultrasoundmagnetic resonance angiographydilution based upon ultrasound, urea, or thermal techniquesStatic venous pressureDuplex ultrasonographyGadolinium-based MRI should be avoided due to nephrogenic systemic fibrosis

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PROSPECTIVE MONITORINGK/DOQI guidelines for surveillance of fistulas :Direct flow measurements Physical findings suggestive of stenosis:arm swellingprolonged bleeding after needle withdrawalcollateral veinsaltered features of the pulse or thrill Duplex ultrasonography Static pressure

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When to refer?More than one abnormalities Persistent abnormalities Access flow rate 0.75

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Treatment of venous stenosisPercutaneous angioplastyEndovascular metallic stentsSurgical revision

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Percutaneous angioplastyCorrects over 80% of stenosis in both native fistulas and synthetic grafts in both venous and arterial outflow tractsThe 2006 K/DOQI guidelines recommend angioplasty if: stenosis in fistula >50%stenosis in graft >50% + (abnormal physical findings, intragraft blood flow

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 morbidityPreserves future access sites

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Endovascular metallic stentsAdvocated as a method of preventing recurrent stenosis after angioplasty Variable results

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Surgical revisionThe gold standard The lowest recurrence rate Generally been replaced by angioplasty: requiring hospitalization extending the fistula site further up the involved extremity

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STRATEGIES TO PREVENT THROMBOSIS Antiplatelet agentsSystemic anticoagulationAntiphospholipid antibodiesFish oilOther preventive therapies

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Antiplatelet agentsDipyridamole, low-dose aspirin w/ or w/o sulfinpyrazone, aspirin + clopidogrelNeither therapy appeared to be effective, the recurrence rate was 78%In patients with new grafts, the rate of thrombosis was reduced by dipyridamole (relative risk 0.35 versus placebo).

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A surprising finding: apparent increase in thrombosis with aspirinone 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

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Systemic anticoagulationA paucity of data existsA multicenter prospective study:warfarin to patients with newly placed PTFE grafts no increasing graft survivalwith significant bleedingWe only administer warfarin to pt with repetitive thrombus but w/o anatomic stenosis

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Antiphospholipid antibodiesLupus anticoagulant and anticardiolipin antibodies 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

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Fish oilOmega-3 fatty acids Inhibit cyclooxygenase, may dampen intimal hyperplasia in vein grafts Among 24 patients with PTFE grafts:At 12 months, the primary patency rate was significantly higher: 77% versus 15%

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Other preventive therapiesEndovascular radiationprevention of vascular access stenosis gamma radiation: effective in animal models in inhibiting intimal hyperplasiacatheter-based irradiation: utilized to prevent restenosis after angioplasty in the coronary circulationprimary patency at 6 months was better: 42% versus 0no difference in secondary patency at 6 (92% versus 91%) or 12 months (44% versus 57%). Gene therapytheoretically effective, result in less systemic toxicity

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TREATMENT OF THROMBOSESThe 2006 K/DOQI guidelinesWith grafts and associated stenosis: Surgical thrombectomyThrombolysisMechanical disruptionWith fistulas:no recommend any approach to the removal of thromboses

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Surgical thrombectomyOutpatient procedurequickvery low complication rateinitially success in 90%However, failure to correct the underlying outflow stenosis leads to rapid rethrombosis

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ThrombolysisAttempts to fistula thrombosis with urokinase and streptokinase, originally yielded disappointing resultsDosing 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

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Mechanical disruptionA study showed:Similar rate of success with surgical thrombectomy and urokinaseconsiderably greater long-term patency The major concern: pulmonary embolionly 1 of 650 had pulmonary embolus2 of 650 developed transient chest pain of undetermined etiology

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K/DOQI goals for treatmentA success rate of 85%:defined by the ability to use the graft at least once post-procedure After percutaneous thrombectomy40% patency at 3 months After surgical thrombectomy50% patency at 6 months 40% patency at 12 months

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SummaryNonthrombotic complications:Infection: 20%Heart failureDistal ischemiaAneurysm and pseudoaneurysmVenous hypertensionMedian nerve injurySeroma formationThrombotic complication: 80-85%

Thanks for your attention!!References:2007 UpToDate The 2006 NKF/Dialysis Outcomes Quality Initiative (K/DOQI) guidelinesThe 2006 Canadian Society of Nephrology hemodialysis guidelines

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