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