Comparison of two methods for heparin monitoring: A semi-automated heparin monitoring device and activated clotting time during extracorporeal circulation

Abstract

Two methods of heparin monitoring, semi-automated in-vivo heparin protamine titration (HPT) and activated clotting time (ACT), were compared in each of sixteen adult patients undergoing extracorporeal circulation (ECC) for coronary artery bypass surgery. The HPT method determined the initial and maintenance level of heparin for ECC, as well as, the amount of protamine needed for neutralization of heparin. ACT determinations were made in parallel to calculate heparin levels, heparin sensitivity, and protamine requirements. ACT determinations increased from 502±31 seconds after heparinization to 739±49 seconds (p<0.05) five minutes after the start of ECC. The HPT method determined heparin sensitivity to be 153±17 secs/mg/kg and this did not change after the institution of ECC. The increase in ACT observed after the start of ECC resulted in an increase in heparin sensitivity from 151±13 secs/mg/kg initially, to 247±17 secs/mg/kg after the institution of ECC (p<0.01). During ECC, the HPT method reported heparin levels which remained near the initial value of 2.40±0.12 mg/kg. The ACT method's initial heparin level of 2.66±0.12 mg/kg rose after the start of ECC to 4.39±0.55 mg/kg (p<0.05). The HPT method adequately predicted protamine requirements, 2.66±0.15 mg/kg protamine vs. 3.47±0.14 mg/kg actual dose while the ACT method predicted excess: 5.02±0.34 mg/kg (p<0.01). In-vivo heparin-protamine titration method provided more consistent information during ECC and directed a significantly smaller dose of protamine for heparin neutralization.