Objective To investigate the effect of methylprednisolone pretreatment on cardiopulmonary bypass(CPB)-induced intestinal barrier injury in patients undergoing cardiac surgery.Methods Ninety NYHA Ⅰor Ⅱ patients,aged 30-50 yr,weighing 50-75 kg,scheduled for elective cardiac surgery with CPB,were randomly divided into 3 gnoups(n =30 each):control group without CPB(group Ⅰ),control group with CPB(group Ⅱ)and administration of methylprednisolone before CPB group(group Ⅲ).Anesthesia was induced with midszolam,fentanyl,etomidate and rocuronium and maintained with intravenous infusion of propofol and intermittent iv boluses of fentanyl and rocuronium.The patients were mechanically ventilated after tracheal intubation.In group Ⅲ,methylprednisolone 10 mg/kg was injected intravenously before operation and CPB.While in groups Ⅰ and Ⅱ,the equal volume of normal saline was injected instead.The blood samples were taken from the central vein before induetion of anesthesia(T1),before CPB(T2),at 30 min after the beginning of CPB(T3),at 30 rin afier the end of CPB(T4)and at 120 min after operation(T5)for determination of the plasma endotoxin concentration.Infection was recorded within 7 days after operation.Results The plasma endotoxin concentrations at T1 were within the normal range in all groups,without significant difference among the three gnoups(P ＞0.05).The plasma endotoxin concentration at T3-5 and incidence of postoperative infection in group Ⅲ were significantly lower than those in group Ⅱ,while higher than those in group Ⅰ(P ＜ 0.05).Conclusion Methylprednisolone pretreatment can reduce CPB-induced impairment of the intestinal harrier function in patients undergoing cardiac surgery.