The relationship between heparin level and activated clotting time in the adult cardiac surgery population.

The purpose of this descriptive study was to examine the relationship between heparin levels (HL) determined by heparin protamine titration (HPT) and activated clotting time (ACT) for cardiopulmonary bypass (CPB) in an adult cardiac surgery population. We examined institutional databases for all patients who underwent CPB at a single US academic institution from February 2005 until July 2007. Baseline ACT, predicted and actual heparin dose response (HDR), target and actual ACT, heparin concentration and heparin bolus dose were recorded. We examined the ACT and HL after the initial heparin bolus dose (Post-Hep) and 10 minutes after the initiation of CPB (CPB+10). The Post-Hep and CPB+10 ACT and HL are reported for 3802 patients. The distribution of ACTs for HL of 0.7, 1.4, 2.0, 2.7 and 3.4 units heparin/mL blood at both time points are reported. Additional analysis of the relationship of HL to ACTs of 300, 350, 400 and 480 seconds is also presented.