Impact of protamine dose on activated clotting time and thromboelastography in infants and small children undergoing cardiopulmonary bypass

Objectives To study the effect of two protamine-dosing strategies on activated clotting time (ACT) and thromboelastography (TEG). Background Protamine dosage based on neutralizing heparin present in the combined estimated blood volumes (EBVs) of the patient and cardiopulmonary bypass (CPB) pump may result in excess protamine and contributes toward a coagulopathy that can be detected by ACT and TEG in pediatric patients. Methods A total of 100 pediatric patients 1month to 5years of age undergoing CPB were included in this retrospective before/after design study. Combined-EBV group consisted of 50 consecutive patients whose protamine dose was calculated to neutralize heparin in the combined EBVs of the patient and the pump. Pt-EBV group consisted of the next 50 consecutive patients whose protamine dose was calculated to neutralize heparin in the patient's EBV. Results Baseline and postprotamine ACTs were similar between groups. Postprotamine heparin assay (Hepcon) showed the absence of residual heparin in both groups. Postprotamine kaolin-heparinase TEG showed that R was prolonged by 7.5min in the Combined-EBV group compared with the Pt-EBV group (mean R of 20.17 vs 12.4min, respectively, P<0.001). Increasing doses of protamine were associated with a corresponding, but nonlinear increase in R. There was no significant difference in the changes for K, alpha, and MA between the groups. Conclusion Automated protamine titration with a protamine dosage based on Pt-EBV can adequately neutralize heparin as assessed by ACT while minimizing prolonging clot initiation time as measured by TEG.