Objective To investigate the effects of sevoflurane postconditioning on myocardial neutrophil infiltration in patients undergoing cardiac valve replacement under cardiopulmonary bypass (CPB).Methods Twenty-four ASA Ⅱ or Ⅲ patients (NYHA Ⅱ or Ⅲ ) of both sexes aged 20-50 yr with BMI of 19-25 kg/m2 undergoing cardiac valve replacement under CPB were randomly divided into 2 groups ( n =12 each):group control (group C) and group sevoflurane postconditioning (group S).Anesthesia was induced with midazolam,fentanyl,etomidate and rocuronium and maintained with iv infusion of fentanyl,midazolam and vecuronium.The patients were intubated and mechanically ventilated (VT 8-10 ml/kg,RR 10-14 bpm,I∶E 1∶2,FiO2 100％ ).PETCO2 was maintained at 35-40 mm Hg.In group S sevoflurane was inhaled immediately after aorta and vena cava were unclamped.The end-tidal sevoflurane concentration was maintained at 1.7％ for 5 min.Arterial blood samples were collected before surgery and at 1,2 and 4 h after aortic unclamping for determination of plasma cardiac troponin T concentration.Myocardial specimens were obtained from right auricular appendage after opening of pericardium and at 1 h after aortic unclamping for microscopic examination and determination of myocardial myeloperoxidase expression.Results Sevoflurane postconditioning significantly decreased plasma cardiac troponin T concentration and myocardial myeloperoxidase expression and ameliorated histo-pathological damage in group S as compared with group C.Conclusion Myocardial neutrophil infiltration is involved in the protective effect of sevoflurane postconditioning against myocardial injury in patients undergoing cardiac valve replacement under CPB.