LOW-MOLECULAR-WEIGHT HEPARIN (FRAGMIN(TM)) VERSUS HEPARIN FOR ANTICOAGULATION DURING CARDIOPULMONARY BYPASS IN OPEN-HEART-SURGERY, USING A PIG MODEL

Fragmin (TM) and heparin were studied in pigs during 120 min of cardio pulmonary bypass (CPB) and up to 240 min postoperatively, with respect to clotting, bleeding and the effects of protamine. Thirty-three pigs received bolus injections of 300IU/kg with or without additional dosa ge during CPB and with or without subsequent protamine sulphate. Doses of Fragmin (TM) 60% higher were necessary to prevent clotting. These had 100% higher anti-FXa levels but about 50% shorter activated coagul ation time (ACT) compared with heparin. Anti-FXa increased with cumula tive doses of heparin and Fragmin (TM) but ACT and activated partial t hromboplastin time (aPTT) did not, indicating a larger loss of thrombi n inhibition compared with anti-FXa in both drugs during CPB. Thrombin inhibition was crucial for prevention of clotting. Protamine efficien tly normalized ACT in the Fragmin (TM) group but left a residual 20% a nti-FXa, which did not increase the bleeding tendency. Fragmin (TM) co uld adequately be monitored with ACT and would be a safe alternative t o heparin in CPB.