Microvascular anastomotic thrombosis is a significant clinical problem, particularly in crush and avulsion injuries. Platelet deposition plays a particularly important role in the initiation and propagation of microvascular thrombosis, whereas thrombin has little effect in the acute phase of thrombus formation. Nevertheless, heparin (a specific thrombin inhibitor) remains the most widely used microvascular irrigant. The purpose of this study was to evaluate tirofiban HCl (Aggrastat), a glycoprotein IIb/IIIa inhibitor, and its role in preventing postoperative thrombosis in a crush anastomosis model.A crush injury model using the rat femoral artery was used. End-to-end microvascular repairs were performed. One milliliter of irrigant was used within the vessel lumen before placement of the last suture. The irrigant used was randomized into one of four groups: lactated Ringer's as a control, tirofiban (50 microg/ml), heparin (100 U/ml), and a combination of heparin (100 U/ml) and tirofiban (50 microg/ml). The vessels were reexamined 24 hours postoperatively and patency was assessed. A total of 62 vessels were used for the study.The patency rate was two of 20 (10 percent) for the control group, 13 of 22 (59 percent) for the tirofiban group, one of 10 (20 percent) for the heparin group, and eight of 10 (80 percent) for the heparin plus tirofiban group. This study demonstrates a statistically significant improvement in patency with tirofiban irrigation in a crush anastomosis rat model when compared with saline or heparin alone.Clinically, tirofiban may have utility as a potent anticoagulant and is potentially useful in microvascular injuries that have a significant crush/avulsion component.