In each group, routine surgery was performed using a membrane oxygenator (Edwards Vital, Edwards Lifesciences LLC, Irvine, CA, USA), a 3-mg/kg dose of sodium heparin, 2 000 ml of Ringer’s lactate primer and a roller pump at a body temperature of 28°C. Cardiopulmonary bypass was instituted via the ascending aorta and single two-stage venous cannulation (maintained at 2.2–2.4 l/min/m2).