Abstract: AIM: To determine the effect-site target concentration (Ce) of sufentanyl at which there was 50% probability of preventing movement from pain in response to the injection rocuronium(EC₅₀). METHODS: Fifty-three ASA Ⅰ patients scheduled for general anesthesia were divided into male group(n=27) and femal group(n=26)according gender.Anesthesia was induced with a propofol target-controlled infusion(TCI Marsh model) and sufentanyl TCI(Bovill model).Effect-site target concentration of propofol was 2.8 μg/mL.Ce of sufentanyl for the first patient started st 0.15 ng/mL.Ce of sufentanyl for each subsequent patient by the Dixon up-and-down method with an interval of 0.02 ng/mL. After both drugs reached target concentration,rocuronium 0.8 mg/kg was administered and the pain response wan observed. RESULTS: The EC₅₀ of sufentanly for preventing rocuronium induced withdrawal movements was (0.080±0.023),(0.103±0.019) ng/mL, respectively in male group and female group. From probit analysis, the EC₅₀ of sufentanly in male group and female group was 0.071 ng/mL(95% confidence limits 0.051-0.085 ng/mL), 0.098 ng/mL(95% confidence limits 0.085-0.108 ng/mL)and the EC₉₅ was 0.103 ng/mL(95% confidence limits 0.087-0.195 ng/mL), 0.120 ng/mL(95% confidence limits 0.109-0.176 ng/mL). EC₅₀ of sufentanly was significant higher in female group than that in male group. CONCLUSION: It is effective to prevent the movement from pain in response to the injection rocuronium with sufentanyl by TCI,and EC₅₀ of sufentanly is significant higher in female patients than that in male patients.

Key words: Up-and-down method, EC₅₀, Sufentanly, Rocuronium