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.