Management of Clotted Hemodialysis Access Grafts

Aalpen A. Patel and Scott Trerotola

Approximately 20 million individuals in the United States have chronic kidney disease, and just as many are at increased risk for development of such disease.¹ In 2004 in the United States alone, 320,000 patients required dialysis (peritoneal dialysis or hemodialysis) for end-stage renal disease.² Because many of these patients require hemodialysis, a reliable long-term dialysis access is their lifeline. Although an increase in fistulas is the goal of the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI) and the Fistula First Initiative, when a suitable vein is not available, use of an artificial graft is the only option. Regardless of whether it is a graft or fistula, thrombosis is inevitable in time, although evidence suggests that the rate may be lower with fistulas. Clotted access may be managed by open surgery (increasingly rarely) or by various endovascular techniques (including mechanical thrombectomy, pharmacologic thrombolysis, and combination techniques, all with associated angioplasty of the culprit lesions). In the past, surgical thrombectomy was the norm. However, in the last decade, endovascular management has replaced open surgery as the primary method of treatment of a thrombosed dialysis access.³

Avoidance of grafts altogether in favor of fistulas will further reduce the need for declotting techniques; a fistula should be created whenever possible. However, grafts will probably always be part of the delivery of hemodialysis in the United States, and thorough familiarity with declotting techniques, results, and complications is essential to any interventionalist. A coordinated effort from a vascular access team consisting of nephrologists, interventionalists, access surgeons, nephrology nurses, and ideally, a vascular access coordinator is critical to achieve optimal outcomes in this population.

In this chapter only the endovascular management of clotted hemodialysis access grafts is discussed.

• Hemodialysis access graft infection or overlying cellulitis. Unlike fistulas, in which thrombophlebitis is common, redness, warmth, and swelling at the access site should be considered infection until proven otherwise. Treatment should begin with intravenous antibiotics. Because the infected material in the graft cannot be cleared with antibiotic therapy alone, subsequent surgical intervention is needed, even if the overlying tissue appears to have healed.

• Uncorrectable coagulopathy

Relative

• Severe allergy to contrast material. Because of the current U.S. Food and Drug Administration (FDA) warning on the use of gadolinium in patients with end-stage renal disease (concern over a possible relationship to nephrogenic fibrosing dermopathy), it should not be used until more evidence is gathered and the issue is resolved.4,5 Pretreatment with prednisone, 40 mg orally 12 and 2 hours before intervention, is usually sufficient for most allergic reactions; some add H₁ and possibly H₂ blockers, but there is little evidence for this.⁶

• Abnormal but correctable coagulation parameters

• Ischemia of the ipsilateral extremity, because restoring flow will worsen the ischemia by exacerbating the steal phenomenon.

• History of a significant right-to-left shunt because of the risk for paradoxical emboli with rare reported strokes from percutaneous declotting.7,8 However, successful and complication-free thrombectomy in patients with a known patent foramen ovale, even with right-to-left shunting, has been reported.⁹

• Significantly reduced pulmonary reserve (pulmonary hypertension, severe lung disease, right heart failure) because of an inability to tolerate the small pulmonary emboli resulting from virtually any form of declotting. Fatal pulmonary emboli have been reported in this population.10,11

• Severe hyperkalemia or acidosis

Equipment

• Access needle/set (angiocatheter, 19-gauge needle, or a micropuncture set)

• 6F short marker-tip sheath

• 7F short marker-tip sheath

• Two infusion catheters or a mechanical percutaneous thrombectomy device (e.g., Arrow-Trerotola PTD)

• Appropriately sized percutaneous transluminal angioplasty (PTA) balloons

• An inflation device or a 1-mL polycarbonate syringe (preferred), 10-mL syringe, and a flow switch

• Contrast material

Technique

Anatomy and Approach

The preferred form of access, arteriovenous fistulas, cannot always be created. When such is the case, 6- to 8-mm or tapered 4- to 7-mm polytetrafluoroethylene (PTFE) grafts or, less commonly, other material such as bovine or porcine xenograft is used to create a dialysis access. Typically, the upper extremities are used and grafts are placed in straight or loop configurations, starting peripherally and moving centrally as grafts fail. Occasionally, more creative approaches in the neck/chest and lower extremities are needed.

Patient Evaluation and Preparation

The importance of clinical evaluation (history, physical examination, and laboratory tests) in the management of a clotted hemodialysis access graft should not be underestimated. It can help the operator prevent futile efforts and avoid complications. The preoperative workup includes a directed history of the dialysis access and previous interventions and a subsequent physical examination.3,12

Determining when the access was created, the type of access in place, and when the graft thrombosis occurred is important. If more than two previous interventions have been performed in less than 1 month, the access may require surgical management. It is critical to determine whether there are signs of local (hemodialysis access graft site) infection (warmth, erythema, tenderness) or systemic infection (fever, chills). If along with physical examination it is determined that graft infection is present, access intervention is absolutely contraindicated.3,12–14 The history should also focus on possible contraindications such as right-to-left shunts and severe pulmonary disease.

Physical examination is just as important. The flow circuit in the extremity should be assessed by palpating and documenting the ipsilateral radial, ulnar, and brachial pulses. Blood supply to the distal part of the extremity must be assessed as well (capillary refill and warmth of the hand/arm). To assess for central venous stenosis or occlusion, chest wall collaterals should be noted with care. If present, it should be determined whether arm swelling was present when the graft was functioning, because swelling may dictate treatment of a central lesion discovered after restoring graft patency.¹⁵ Cardiac and pulmonary examinations are also important to assess for signs of significant fluid overload.^3,12–14 In addition, each graft should be evaluated by physical examination before every intervention. The site should be assessed for warmth, tenderness, and erythema, because these symptoms may indicate graft infection or cellulitis. To choose optimal puncture sites for intervention, one must determine the type of access (straight or loop), direction of inflow and outflow, presence of aneurysmal graft degeneration, and type of anastomosis.^3,12

Before hemodialysis access graft intervention, coagulation parameters (international normalized ratio [INR] and platelet count) should be determined and confirmed to be in the normal range. In the authors’ practice, the values used are an INR less than 2.0 (<1.5 for central PTA) and a platelet count above 25,000. It is important to have normal or reversible values of the coagulation parameters in case graft or vascular rupture occurs during the intervention.

A few cases of postprocedure septic shock have been reported, and colonization of clotted grafts is very common.¹⁶ Therefore (though not evidence based), most interventionalists give preprocedural prophylactic antibiotics (cefazolin [Ancef], 1 g intravenously). To prevent rethrombosis during the procedure, as well as to blunt any pulmonary vasospastic or bronchospastic response to small pulmonary emboli occurring during declotting, 3000 to 5000 units of heparin should be administered before intervention.