Heparin dose for accurate anticoagulation in cardiac surgery.

A simplified technique relating individual heparin dose to desired anticoagulant effect was used in 152 patients during cardiac surgery. Activated clotting time (act) was measured by semi-automated technique (Hemochron) before and after heparin, 200 U/kg I.V. Two point linear dose-response curve allowed calculation of any additional heparin required for uniform ACT of 480 seconds. Mean heparin requirement was 330 U/kg) (range 200--600 U/kg) mean requirements for adults (mean = 310 U/kg) were significantly less (p less than 0.001) than for children (mean = 430 U/kg). Individual dose-response curves suggested 20 patients (13%) could have been below adequate anticoagulant levels (ACT less than 300 seconds) using our previous formula for heparin dosage (9000 U/m2). At completion of cardiopulmonary bypass, measurement of ACT provided circulating heparin level from the dose-response curve. Protamine dose (1.3 mg/100 U. heparin) was individualized to precisely reverse anticoagulant effect to control ACT in 127 of 152 patients (84%) with a single dose. Elimination of patient and product variability by simplified semi-automated dose-response technique for heparin therapy provides uniform anticoagulant effect and its accurate neutralization. This technique is recommended for precise anticoagulant therapy during open heart surgery.