Management of Clotted Hemodialysis Access Grafts

Absolute

• 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.

• Indication for urgent/emergent hemodialysis (e.g., acidosis, severe hyperkalemia, fluid overload).

• Uncorrectable coagulopathy.

Relative

• Severe allergy to contrast material. Gadolinium-based agents should not be used in patients with end-stage renal disease because of the relationship to nephrogenic sclerosing fibrosis. Pretreatment with prednisone and diphenhydramine beginning 13 hours before intervention is usually sufficient for most allergic reactions.

• Abnormal but correctable coagulation parameters.

• Ischemia of the ipsilateral extremity (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. However, successful and complication-free thrombectomy in patients with a known patent foramen ovale, even with right-to-left shunting, has been reported.

• Significantly reduced pulmonary reserve (pulmonary hypertension, severe lung disease, right-sided 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.

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 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.

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 hemodialysis access graft infection (warmth, erythema, tenderness) or systemic infection (fever, chills, elevated white blood cell count, bacteremia). If along with physical examination it is determined that graft infection is present, access intervention is absolutely contraindicated. 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. 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. Cardiac and pulmonary examinations are also important to assess for signs of significant fluid overload. 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.

Before hemodialysis access graft intervention, coagulation parameters should be determined and confirmed. 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 common. Therefore (although not evidence based) most interventionalists give preprocedural prophylactic antibiotics (cefazolin [Ancef], intravenously, based on weight). To prevent rethrombosis during the procedure and 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.

Technical Aspects

Both open surgical and endovascular approaches can be used to declot a thrombosed hemodialysis access graft. Only endovascular approaches (mechanical thrombolysis, pharmacologic thrombolysis, and combination approaches) are addressed in this chapter. Thrombolysis of a hemodialysis access graft has two major steps: clot removal ( Fig. 81.1 ) (including the arterial plug [ Fig. 81.2 ]) and treatment of the underlying anatomic lesion ( Fig. 81.3 ). In the absence of infection, there are usually underlying causes (e.g., stenoses at the venous or arterial anastomoses, outflow veins, or, rarely, arteries proximal to the arterial anastomosis) that have to be addressed with PTA. There is growing evidence for stent-graft placement for stenosis at the venous anastomosis of dialysis access grafts; however, evidence for effectiveness and durability in the setting of graft thrombosis remains limited. Some common techniques, but not all techniques, are described in this chapter; it is not meant to be a comprehensive review. Many excellent review articles are listed in the Suggested Readings at the end of this chapter.