Clinical experience with the activated clotting time for the control of heparin and protamine therapy during cardiopulmonary bypass.

The clinical experience with the activated clotting time (ACT) for the control of heparin and protamine therapy during cardiopulmonary bypass in 70 patients (50 adults and 20 children) is reviewed. After a standard dose of 2 mg/kg of body weight of heparin, the patient's ACT ranged from 210 to more than 600 seconds. The heparin dose required to accomplish an ACT of 500 seconds ranged from 1.3 to 4.7 mg/kg for adults and from 2 to 4.5 mg/kg for children. At the termination of bypass, the assessment of the patient's heparin level with the ACT allowed a more accurate reversal with protamine and markedly reduced the protamine requirements. Although the postoperative drainage was not significantly decreased, the total amount of blood transfusion and fresh-frozen plasma and platelet requirements were reduced by 30%, 20%, and 20% respectively. The simple, easy-to-use protocol is presented in detail.