Detection of Protamine and Heparin After Termination of Cardiopulmonary Bypass by Thrombelastometry (ROTEM®): Results of a Pilot Study

Abstract

Our goal of this study was to determine whether protamine's effects on coagulation can be detected and differentiated from those of heparin when using thrombelastometry (ROTEM). To reverse the effects of heparin after cardiopulmonary bypass (CPB), 22 consecutive patients undergoing aortocoronary bypass graft surgery were included. According to clinical routine, all patients received a first dose of protamine calculated from the total amount of heparin given; additional protamine (70 U/kg) was administered to patients with activated clotting time (ACT) above baseline and clinical signs of diffuse bleeding. Simultaneously, routine ACT measurements, ROTEM assays (heparin-sensitive INTEM, and heparinase-containing HEPTEM test) and standard coagulation tests were performed, and the activity of coagulation factors as well as antifactor Xa activity measured. Administration of additional protamine (n = 16) resulted in a statistically significant increase in coagulation times on the intrinsically activated test (INTEM-CT), namely from (mean [+/-SD]) 219.8 (+/-19.1) s to 241.1 (+/-21.7) s (P < 0.001), and on the heparinase-containing test (HEPTEM-CT), namely from 210.2 (+/-19.9) s to 226.8 (+/-21.8) s (P < 0.001). These changes were not observed in patients receiving a single protamine dose (n = 6). The INTEM-CT:HEPTEM-CT ratio correctly identified 56 of the 58 samples as not containing residual heparin and correctly detected residual heparin in 3 of the only 6 samples showing elevated antifactor Xa values after CPB. Our preliminary data show that at termination of CPB administration of additional protamine results in a brief prolongation of coagulation times on the INTEM and HEPTEM test and that ROTEM might be useful in excluding residual heparin in cases showing prolonged ACT.