A comparison of heparinised saline irrigation solutions in a model of microvascular thrombosis

The use of heparinised irrigation solutions has become common in microvascular surgery, but the concentration of heparin has been determined empirically. A laboratory model of microvascular thrombosis, employing a crush injury, intimal abrasion, and stasis to the rat superficial femoral artery was used to compare heparinised saline irrigation solutions of various concentrations. The solutions included normal saline (Group I, controls) and heparinised normal saline in concentrations of 10 U/ml (Group III), 250 U/ml (Group IV), and 500 U/ml (Group V). Group I animals had a patency rate of 25% at 20 min and 0% at 24 h. Group II showed a patency rate of 75% at 20 min but fell to 37.5% at 24 h. Patency in Group III was 87.5% at 20 min and at 24 h. Group IV had a 100% patency rate at 20 min and at 24 h. Group V animals were 100% patent at 20 min and 87.5% patent at 24 h. The activated partial thromboplastin time was prolonged in animals exposed to 250 U/ml and 500 U/ml of heparinised saline. Patency was significantly improved in animals exposed to 100 U/ml, 250 U/ml and 500 U/ml when compared to the control group (p less than 0.001). These results suggest that topical heparinised saline administration is of benefit in the prevention of microvascular thrombosis. Higher concentrations tested in this study resulted in a significant increase in patency, but also prolonged the activated partial thromboplastin time. 100 U/ml is the ideal concentration of heparinised saline irrigation because it significantly improved patency but did not produce detectable systemic effects in this model.