Prevention of microvascular thrombosis with controlled-release transmural heparin.

The use of controlled local-release heparin was studied as a means to prevent thrombosis in microvascular surgery, using a rat arterial inversion graft as a model. Polyvinyl alcohol embedded with heparin was placed around the outside of inversion graft anastomoses in 16 animals. Results were compared with control group animals in which polyvinyl alcohol alone was placed around the graft or systemic heparin was given. Vessel patency rates were significantly higher for animals receiving either systemic or transmural heparin than for animals in the control group. Controlled local delivery of heparin did not cause measurable systemic anticoagulation. However, the complication of local hematoma formation occurred as frequently as in the systemic heparin group. Controlled transmural release of heparin has an effective local antithrombotic effect and may hold promise for use in clinical practice.