Thrombosis Prophylaxis in Pancreas Transplantation?

Robert J. Stratta, MD

Disclosures

September 11, 2002

Question

What are your recommendations for thrombosis prophylaxis in pancreas transplantation?

Response from Robert J. Stratta, MD

Unlike other solid organ transplants, the pancreas graft is uniquely prone to vascular thrombosis due to intrinsically low microcirculatory flow. The arterial blood supply to the pancreas is based on collateral circulation and is parasitized from the splenic and superior mesenteric arteries. Putative risk factors for pancreas allograft thrombosis include solitary pancreas transplantation, donor age above 40 years, cardiovascular or cerebrovascular cause of donor brain death (nontraumatic), preservation time in excess of 30 hours, donor or recipient body mass index > 30 kg/m2, use of a venous extension graft, left-sided pancreas graft, recipient age above 45 years, and preexisting hypercoagulable state.

In patients with a history of deep venous thrombosis, recurrent arterio-venous access thrombosis, myocardial infarction, cerebrovascular event, family history of thrombosis, multiple miscarriages, prior allograft thrombosis, polycythemia, thrombocytosis, or thrombotic microangiography, we perform a hypercoagulation work-up including a thrombophilia screen (plasminogen activity, free protein S level, protein C activity, Factor V Leiden, antithrombin III level), anticardiolipin antibodies, antiphospholipid antibodies, PT/PTT/INR, platelet count, fibrinogen level, and homocysteine level. The incidence of pancreas allograft thrombosis is 5% to 7% following pancreas-kidney transplantation and 10% to 12% after solitary pancreas transplantation. It is uncertain whether the risk of thrombosis is higher in preemptive pancreas-kidney transplantation vs transplantation in patients on dialysis.

Consequently, we administer antiplatelet therapy to all pancreas transplant recipients (aspirin 81 mg/day). In solitary pancreas transplant recipients or pancreas-kidney recipients with any of the above stated risk factors or evidence of hypercoagulability, we have adopted the "Maryland" protocol and administer 2500 units of heparin intraoperatively prior to clamping the vessels for pancreas implantation, followed by a postoperative regimen of a continuous infusion of heparin at 300 units/hour for 24 hours, then 400 units/hour for 24 hours, then 500 units/hour until postoperative day 5, at which time the heparin is stopped and the patient is placed on warfarin 1 mg/day for 1-2 months. We do not strive to achieve either therapeutic PT or PTT levels. In our experience, therapeutic anticoagulation results in a high risk of bleeding and may potentiate allograft pancreatitis. Our limited experience with dextran, enoxaparin, and ticlopidine has been negative (excessive risk of bleeding). Safe and effective anticoagulation strategies are a key to successful pancreas transplantation, especially solitary pancreas transplantation or with extended criteria donors or recipients.

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