Fig. 1. Mean ± SD measured sufentanil concentrations before and after the start of cardiopulmonary bypass (CPB) and before and after termination of CPB. The gray horizontal lines represent the target sufentanil concentrations for each period. Pre CPB = just before CPB; CPB + 5 = 5 min after the start of CPB; CPB + 30 = 30 min after the start of CPB; Last CPB = last sample drawn during CPB; Post CPB = just after separation from CPB; End Surgery = end of surgery .