The effect of low-molecular-weight heparin on microvenous thrombosis in a rat model.

OBJECTIVE To assess the impact of a low-molecular-weight heparin sodium, dalteparin sodium, on a thrombogenic microvenous anastomosis, using a randomized, blinded animal model. METHODS Using male Sprague-Dawley rats, 70 IU/kg of dalteparin sodium (for the treatment group) or isotonic sodium chloride solution (for the control group) were administered subcutaneously in a blinded randomized fashion. Using microsurgical techniques, the femoral venous pedicle was isolated bilaterally. A tuck anastomosis was then performed on each side. Vessel patency was assessed periodically for 3 hours using a strip and refill test. Patency or thrombosis was confirmed by cutting the vessel proximal to the anastomosis and examining the lumen for thrombus. RESULTS A total of 58 venous tuck anastomoses were performed. There was no difference in bleeding complications between the treatment and control groups. The control group had a thrombosis rate of 50%, and the treatment group had a thrombosis rate of 60%. The chi2 analysis does not indicate a statistical difference between these 2 groups (P = .59). CONCLUSION Low-molecular-weight heparin, at standard therapeutic dosing, may not provide an adequate antithrombotic effect to prevent anastomotic thrombosis in free tissue transfer.