Mechanisms and attenuation of hemostatic activation during extracorporeal circulation

Patients undergoing cardiac surgery with cardiopulmonary bypass are at risk for excessive microvascular bleeding, which often leads to transfusion of allogeneic blood and blood components as well as reexploration in a smaller subset of patients. Excessive bleeding after cardiac surgery is generally related to a combination of several alterations in the hemostatic system pe rtaining to hemodilution, excessive activation of the hemostatic system, an d potentially the use of newer, longer-acting antiplatelet or antithromboti c agents. Although several nonpharmacologic strategies have been proposed, this review summarizes the role of pharmacologic interventions as means to attenuate the alterations in the hemostatic system during CPB in an attempt to reduce excessive bleeding, transfusion, and reexploration. Specifically , agents that inhibit platelets, fibrinolysis, factor Xa and thrombin, as w ell as broad-spectrum agents, have been investigated with respect to their role in reducing consumption of clotting factors and better preservation of platelet function. Prophylactic administration of agents with antifibrinol ytic, anticoagulant, and possibly antiinflammatory properties can decrease blood loss and transfusion. Although aprotinin seems to be the most effecti ve blood conservation agent (which is most likely related to its broad-spec trum nature), agents with isolated antifibrinolytic properties may be as ef fective in low-risk patients. The ability to reduce blood product transfusi ons and to decrease operative times and reexploration rates favorably affec ts patient outcomes, availability of blood products, and overall health car e costs. (C) 2001 by The Society of Thoracic Surgeons.