Physiologic alteration of fibrinogen levels: influence upon patency of microvenous anastomoses.

High baseline levels of plasma fibrinogen have been correlated with increased risk for cardiovascular disease. Since fibrinogen plays a central role in both coagulation and platelet aggregation and is a primary component of thrombi, this study was designed to assess the relationship of circulating fibrinogen concentration and vein anastomotic patency. Subcutaneously injected turpentine was used to increase, and intravenous ancrod (snake venom) to decrease, plasma fibrinogen levels. Rat femoral vein anastomoses were performed, and patency was assessed after 120 min of flow. Rat tail bleeding times were obtained, and blood samples were drawn to determine fibrinogen and plasma protein concentrations, Lee-White clotting times, and activated partial thromboplastin times (APTT). Increased patency was found in the ancrod group (88%) (P < 0.05 vs. controls); turpentine-treated and control groups were not significantly different (71% and 63%, respectively). The ancrod group also showed significantly prolonged tail bleeding times and APTT. Fibrinogen levels were significantly decreased in the ancrod group (1.73 mg/ml) and elevated in the turpentine group (4.91 mg/ml) vs. controls (2.34 mg/ml; P < 0.005). These results indicate that elevated fibrinogen levels, in particular when triggered by an acute-phase response, do not appear to predispose small vessel repairs toward thrombosis. Furthermore, this study supports the use of ancrod as an anticoagulant for microvascular surgery.