Thrombosis After Pancreas Transplantation
Because of the high risk of posttransplant pancreatic allograft thrombosis, are there guidelines for anticoagulation in pancreas transplant recipients?

Junaid Ahmed, MD

Unlike other solid organ transplants, the pancreas graft is uniquely prone to vascular (particularly venous) thrombosis due to intrinsically slow 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 > 40 years, cardiovascular or cerebrovascular cause of donor brain death (ie, nontraumatic), simultaneous small bowel and pancreas retrieval, preservation time in > 24 hours, donor or recipient body mass index > 28 kg/m, use of a venous extension graft, left-sided pancreas graft placement, recipient age > 45 years, and preexisting hypercoagulable state. Whether preemptive kidney-pancreas transplantation, in the absence of uremia, is a risk factor for pancreas allograft thrombosis remains conjectural. The incidence of pancreas allograft thrombosis is 5% to 7% following pancreas-kidney and 10% to 12% following solitary pancreas transplantation in the absence of thrombosis prophylaxis.

Consequently, we administer antiplatelet therapy (aspirin 81 mg/day) to all pancreas transplant recipients. 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 intravenous heparin intraoperatively just prior to clamping the vessels for pancreas implantation. This heparin bolus is 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, aspirin is begun, and the patient is placed on warfarin 1 mg/day for 1-2 months. We do not strive to achieve either therapeutic prothrombin time (INR) or partial thromboplastin time (PTT) levels. In fact, if the INR or PTT begin to rise, then we back down on the dosing of either warfarin or heparin. In our experience, therapeutic anticoagulation results in a high risk of bleeding complications 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.