Normothermic cardiopulmonary bypass increases heparin requirements necessary to maintain anticoagulation

Objective. With the practice of warm cardiopulmonary bypass (CPB) at our in stitution we have observed an apparent increase in heparin requirements. CP B temperature predictability affects pharmacokinetics and differences in dr ug metabolism can be expected. We hypothesized that heparin requirements wo uld increase with increasing CPB temperature. Methods. Following Institutio nal Review Board approval, we reviewed the charts of 354 patients undergoin g primary coronary artery bypass graft surgery. We recorded patient demogra phic data, CPB duration, heparin requirements, and temperature during CPB. CPB was conducted between 24 degrees C and 37 degrees C. The Spearman's cor relation coefficient, Pearson chi-square, and rank-sum tests were used for data analysis. Results. Core temperature during CPB correlated with heparin requirements (r = 0.13, p < 0.02). However, CPB duration was shorter in wa rm patients than in cold patients (r = -0.455, p < 0.0001). Additional hepa rin requirements adjusted for duration of CPB (units/minute) were also sign ificantly greater in the warm group (p = 0.018). Conclusions. Maintenance o f adequate heparin anticoagulation during CPB is clinically important. Warm CPB patients required more heparin per minute than those undergoing cold C PB, More frequent assessment of anticoagulation and administration of addit ional heparin should be considered in patients undergoing warm CPB.