Objective To evaluate the effect of low-flow sevoflurane anesthesia on the early postoperative renal function in patients.Methods Sixty patients of both sexes,of American Society of Anesthesiologists physical status Ⅰ or Ⅱ,aged 18-64 yr,scheduled for elective non-urological surgery with general anesthesia,with an expected surgical duration＞4 h,were divided into 2 groups (n =30 each) using a random number table method:middle-flow anesthesia group (group Ⅰ) and low-flow anesthesia group (group Ⅱ).Anesthesia was induced with Ⅳ midazolam,sufentanil,propofol and cisatracurium besylate.Mechanical ventilation was performed after tracheal intubation.Pure oxygen served as carrier,the fresh gas flow of oxygen was set at 4-5 L/min,sevoflurane was inhaled for 10-15 min,and then fresh gas flow was decreased to 2 L/min (group Ⅰ) and 0.5 L/min (group Ⅱ).End-tidal pressure of carbon dioxide was maintained at 35-45 mmHg.The end-tidal concentration of sevoflurane was set at 2.0％-2.4％,remifentanil and cisatracurium besylate were infused intravenously,and sufentanill or propofol was injected intermittently to maintain anesthesia.Bispectral index value was maintained at 40-60 during operation.Before anesthesia induction (T0),at 1,2,3 and 4 h after anesthesia induction (T1-4),immediately after operation (T5) and at 24 h after operation (T6),peripheral venous blood samples were collected for determination of serum fluoride ion concentrations.Peripheral venous blood samples and urine specimens were collected at T0,T5,T6,48 h after operation (T7) and 72 h after operation (T8) for determination of creatinine (Cr),blood urea nitrogen (BUN) and cystatin C (Cys C) and serum and urine β2-microglobulin (β2-MG) concentrations.Results Compared with the baseline at T0,serum fluoride ion concentrations were significantly increased at T1-6 in two groups,the serum Cys C concentration was increased at T5,and serum and urine β2-MG concentrations were increased at T5 and T6 in group Ⅰ,serum Cr and BUN concentrations and serum and urine β2-MG concentrations were increased at T5 and T6,and the serum Cys C concentration was increased at T5-T7 in group Ⅱ (P＜0.05).Compared with group Ⅰ,serum fluoride concentrations were significantly increased at T1-6,serum Cr and BUN concentrations and serum and urine β2-MG concentrations were increased at T5,and serum Cys C concentrations at T5-T7 and urine β2-MG concentrations at T5 and T6 were increased in group Ⅱ (P＜0.05).Conclusion Low-flow sevoflurane anesthesia produces no marked effect on early postoperative renal function in patients.