Prevention of venous thrombosis in microvascular surgery by transmural release of heparin from a polyanhydride polymer

Background. The effects of transmurally relased heparin on the patency of microvenous anastomoses were studied by using a bioerodible polymer delivery system in a rat microvascular thrombosis model. Methods. A polyanhydride carrier with heparin was wrapped around the outside of a highly thrombogenic venous inversion graft in 14 animals, and patency rates were compared with those of 17 control animals. Results. Anastomotic patency was significantly greater in the groups treated with transmurrally released heparin, measured both at 24 hours (86% versus 16%; p<0.02) and at 7 days (86% versus 36%; p<0.05) after operation. No significant complications occurred. Conclusions. Controlled release of heparin by transmural delivery is an effective and safe form of local antithrombotic therapy and may have applications both in microvascular and large vessel surgery.