EFFECT OF LOW-DOSE APROTININ ON COAGULATION AND FIBRINOLYSIS IN CARDIOPULMONARY BYPASS

To study the effect of low-dose aprotinin on hemostasis in patients un dergoing cardiopulmonary bypass (CPB) for coronary artery bypass opera tions and to elucidate the mechanism of aprotinin action, we randomize d 14 of 27 patients to receive 30,000 KIU/kg aprotinin in the CPB prim ing volume and 7,500 KIU/kg aprotinin intravenously each hour during C PB (1 patient was excluded from the aprotinin group because of protami ne shock). Intraoperative and postoperative blood loss was significant ly reduced in the aprotinin group. Antithrombin III level was signific antly decreased, and the levels of thrombin-antithrombin III complexes were significantly increased during CPB in both groups, indicating ac tivation of the clotting system. The marked increase in fibrin(ogen) d egradation products during CPB in the control group, indicating enhanc ed fibrinolytic activity, was significantly reduced in the aprotinin g roup. Alpha2-Plasmin inhibitor was significantly reduced during CPB in the control group. The marked increase in alpha2-plasmin inhibitor-pl asmin complexes in the control group, indicating plasmin activity, was significantly reduced in the aprotinin group. A marked decrease in th e platelet count was observed during CPB similarly in both groups. The se findings demonstrated that low-dose aprotinin administration was ef fective in reducing intraoperative and postoperative blood loss and th at activation of the clotting system during CPB was not followed by hy perfibrinolysis in aprotinin-treated patients. The improved hemostasis is mainly attributable to the prevention of hyperfibrinolysis during CPB.