Objective To investigate the effect of dexmedetomidine on systemic vascular resistance in patients undergoing cardiopulmonary bypass. Methods Thirty-one patients undergoing cardiac surgery with cardiopulmonary bypass from January to April, 2012 were randomized into experimental group(n=16) and control group(n=15). The flow rate was kept at 2.4 L/(min·m2) and moderate hypothermia was maintained. Equivalent dexmedetomidine and 0.9% sodium chloride solution were pumped for the experimental group and control gr...