Effects of intraarterial thrombin in the swine model

PURPOSE: To evaluate the effects of catheter-directed thrombin in the perip heral arterial circulation of swine. MATERIALS AND METHODS: Thrombin was injected into a single femoral artery i n 20 domestic swine. Each of five animals from four dose groups received 50 , 150, 250, or 1,000 U as a single dose. Bilateral femoral arterial flow wa s monitored for as long as 4 hours and evaluated relative to baseline and c ontralateral limb flow. Interval arteriographic results were evaluated by s egmental patency and a numeric angiographic score. RESULTS: Mean baseline flow was 136 mL/min +/- 44, with an internal arteria l diameter of 3.4 mm +/- 0.5. A transient increase in blood flow after thro mbin administration was followed by diminished flow and thrombosis. These f indings varied directly with dose and inversely with baseline flow. Angiogr aphic and flow abnormalities generally improved with time and recovery was generally better in swine that received 50 or 1,000 U than in other groups. However, one animal that received 1,000 U (13.2 U/mL/min) developed stable , complete limb thrombosis. The degree of recovery varied with thrombin dos e and thrombus location. At doses greater than 50 U (0.33 u/ml/min +/- 0.05 ), abnormalities were commonly persistent. Animals receiving the 150-U dose (1.33 U/mL/min +/- 0.41) had a higher incidence of persistent distal occlu sion. Distal occlusions were less likely to resolve than proximal occlusion s. CONCLUSIONS: The effect of intraarterial thrombin is directly related to do se and inversely related to baseline blood flow. In swine, a threshold for significant flow disruption and thrombosis exists above a dose of 50 U (0.3 3 U/mL/min +/- 0.05). A threshold dose for irreversible occlusion may also exist. Although small amounts of thrombin in a high-flow vessel may not cau se significant complication, administration into the arterial circulation s hould be avoided.