Effects of different target concentrations of sufentanil on MAC_(BAR) of sevoflurane in patients undergoing abdominal surgery

Objective To investigate the effects of three different effect-site concentration (Ce) of sufentanil given by TCI on the minimum alveolar concentration of sevoflurane for blunting adrenergic responses to skin incision(MAC_(BAR))in patients undergoing abdominal surgery.Methods Eighty ASAⅠ orⅡ patients,aged 20-60 yr,body mass index<30 kg/m~2,undergoing elective abdominal surgery,were randomly divided into 4 groups(n=20 each):control group(group so)and 3 sufentanil groups(group S_1,S_2,S_3).The patients were unpremedicated.Anesthesia was induced with TCI of propofol(target plasma concentration 3.5 μg/ml)and TCI of remifentanil(Ce 4 ng/ml).nacheal intubation was facilitated with rocuronium 0.6 mg/kg after the patients lost consciousness.The patients were mechanically ventilated.And then propofol and remifentanil were immediately stopped and anesthesia was maintained with inhalation of sevoflurane and a mixture of nitrous oxide and oxygen,fresh gas flow set at 10 L/min maintaining for at least 20 min.In group S_0,sufentanil was not given after intubation.In group S_1,S_2 and S_3,TCI of sufentamil was started after intubation at Ce of 0.12,0.18 and 0.24 ng/ml respectively.In group S_0,S_1,S_2 and S_3,sevoflurane inhalation was started with the initial end-tidal concentration of 3.0%,1.8%,1.3% and 1.1% respectively.The patients'response to skin incision was described as positive if MAP or HR increased by≥25%,or negative(MAP or HR increased by<25%).If the response was positive,the end-tidal concentration of sevoflurane for the next patient was increased by 1.2 times,while if negative,decreased by 1.2 times.The sevoflurane MAC_(BAR) was determined by up-and-down sequential trial.Results Compared with group S_0,the MAC_(BAR) of sevotlurane was significantly decreased in group S_1,S_2 and S_3(P<0.05).Compared with group S_1,the MACB_(BAR) of sevoflurane was significantly decreased in group S_2 and S_3(P<0.05).No significant difference was found in the MACB_(BAR) of sevoflurane between group S_2 and S_3 (P<0.05).Conclusion TCI of sufentanil at Ce of 0.12,0.18 and 0.24 ng/ml can significantly reduce MAC_(BAR) of sevoflurane and enhance the inhibitory effect of sevoflurane on stress response in a concentration-dependent manner. Key words: Anesthetics,inhalation; Sufentanil; Drug delivery systems; Dose-response relationship,drug; Stress