Topical heparin enhances patency in a rat model of arterial thrombosis.

Heparin added to irrigation solutions and used in microvascular surgery may have activity as a topical antithrombotic agent. A rat model of arterial thrombosis was used to evaluate topical heparin for preventing thrombosis. A crush injury was applied to both femoral arteries, and then they were transected and anastomosed. The vessel on one side of each rat was washed out and the wound irrigated with physiological saline containing one of three concentrations of heparin: 0, 100, or 500 U/ml. The vessel on the contralateral side was irrigated with unheparinized saline throughout. Patency rates at 24 hours were 63% (10 of 16) for vessels irrigated with either 100 or 500 U/ml of heparin. The contralateral vessels had 24-hour patencies of 19% (3 of 16) for each group (p < 0.05). The group receiving bilateral, unheparinized irrigation had a 24-hour patency of 29% (8 of 28). Activated partial thromboplastin times were significantly prolonged (p < 0.05) 20 minutes into the recirculation for the groups receiving 100 or 500 U/ml of heparin: 44 +/- 3 and 62 +/- 6 seconds (mean +/- standard error of the mean), respectively, in comparison to averages of 33 to 35 seconds at 24 hours in all groups and at 20 minutes after reflow in the control group. This study indicates that heparin added to the irrigation solution significantly enhances patency in compromised arterial anastomoses. The results also indicate a pitfall with studying topical heparin for microvascular surgery in rat models: acute elevation of activated partial thromboplastin time values.