Heparin administration during extracorporeal circulation: heparin rebound and postoperative bleeding.

The individual variations in heparin dose response and heparin activity decay have indicated limitations of the protocols based on body surface area and weight of the patients. In the present study the heparin levels and simpler clotting tests were monitored in a consecutive series of 71 patients undergoing standard cardiac operations. The clotting tests used were the Celite activated clotting time (Celite ACT) and the whole blood activated recalcification time (BART). Forty-four patients received a loading dose of heparin, 3 mg. per kilogram, a maintenance dose of heparin, 1.5 mg. per kilogram per hour, and 6 mg. of protamine sulfate per kilogram at the termination of extracorporeal circulation (ECC) (Protocol I). Twenty-seven patients received a similar initial dose, but the maintenance dose of heparin and the dosage of protamine sulfate were administered according to the measured heparin levels (Protocol II). A significant difference was seen in the measured heparin levels (p less than 0.01, Celite ACT (p less than 0.01), and BART (p less than 0.01) in patients on Protocols I and II. Ten of the 24 patients on Protocol I and none on Protocol II showed heparin rebound phenomenon, and blood loss in patients on Protocol I was significantly greater than that in patients on Protocol II. The study clearly demonstrates that our protocol of heparin administration and control with simpler tests ensures safe hypocoagulation during ECC and efficient reversal at the end, with minimal postoperative blood loss.