Heparin therapy during extracorporeal circulation. II. The use of a dose-response curve to individualize heparin and protamine dosage.

Because the administration of heparin and protamine according to a set protocol will fail to anticoagulate safely or neutralize appropriately a significant number of patients, a method of monitoring heparin therapy during cardiopulmonary bypass is presented. A dose response curve relating heparin dosage to its effect on the activated coagulation time (ACT) can be determined with sufficient accuracy for clinical purposes from three ACT's. Preparation of such a curve makes it possible to maintain anticoagulation in a safe range during bypass and minimizes the number of monitoring tests of coagulation required. At the conclusion of bypass, this curve can be used to predict the precise amount of protamine needed for neutralization. Freed from the confusing effects of hyperheparinemia or protamine excess, the physician can diagnose and treat postoperative bleeding problems much more readily.