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The complications of AV access for hemodialysis .ppt
 

The complications of AV access for hemodialysis .ppt

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    The complications of AV access for hemodialysis .ppt The complications of AV access for hemodialysis .ppt Presentation Transcript

    • 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 2007-04-09 Ri 陳昱潤
    • Chronic hemodialysis vascular access: Types and placement
      • AV fistulas
      • Synthetic grafts
      • Tunneled cuffed catheters
    • AV fistulas
      • End-to-side vein-to-artery anastomosis
      • The 2005 Canadian and 2006 United States K/DOQI guidelines:
        • radiocephalic
        • brachiocephalic
        • brachiobasilic
        • Brachial artery and median antecubital vein
    • Synthetic grafts
      • Polytetrafluoroethylene (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
    • 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 immediate surgery
      • Paresthesia, sense of coolness with retained 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 effect
    • 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 where intraluminal pressure is higher
      • Occur at the distal end if there is significant central venous obstruction
      • Fistulogram to exclude central venous stenosis
    • Thrombotic complications
    • Introduction
      • The 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 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 endothelial cell surface
      • leukocyte 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
    • PROSPECTIVE MONITORING K/DOQI guidelines for surveillance of grafts :
      • Intra-access flow:
        • duplex and variable flow Doppler ultrasound
        • magnetic resonance angiography
        • dilution based upon ultrasound, urea, or thermal techniques
      • Static venous pressure
      • Duplex ultrasonography
      • Gadolinium-based MRI should be avoided due to nephrogenic systemic fibrosis
    • PROSPECTIVE MONITORING K/DOQI guidelines for surveillance of fistulas :
      • Direct flow measurements
      • Physical findings suggestive of stenosis:
        • arm swelling
        • prolonged bleeding after needle withdrawal
        • 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 findings, 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 sulfinpyrazone, aspirin + clopidogrel
      • Neither 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).
      • 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 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
    • Fish oil
      • Omega-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%
    • 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 THROMBOSES The 2006 K/DOQI guidelines
      • With grafts and associated stenosis:
        • Surgical thrombectomy
        • Thrombolysis
        • Mechanical disruption
      • With fistulas:
        • no recommend any approach to the removal 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 urokinase 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 thrombectomy 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