Objective To determine the median effective dose ( ED50 ) of sufentanil blunting re?sponses to double?lumen endotracheal intubation when combined with propofol. Methods American Socie?ty of Anesthesiologists physical statusⅠorⅡpatients, aged 45-64 yr, with body mass index<30 kg∕m2 , of Mallampati classⅠor Ⅱ, undergoing elective thoracic surgery under general anesthesia, were enrolled. Sufentanil was injected intravenously with the initial dose of 0?6μg∕kg, and then propofol 1 mg∕kg was in?jected slowly until the patients lost consciousness. After loss of consciousness, cisatracurium 0?3 mg∕kg was injected intravenously, and propofol 0-1?5 mg∕kg was injected intermittently to maintain bispectral index value ranging from 45 to 55. A double?lumen endotracheal tube was placed at 3 min after administrattion of muscle relaxants. The dose of sufentanil was determined by modified Dixon′s up?and?down method. The dose of sufentanil was increased∕decreased by 0?1 μg∕kg in the next patient. At least 6 independent cross?over pairs were observed, and the test was completed. The response to double?lumen endotracheal intuba?tion was defined as an increase in mean arterial pressure ≥ 20% of the baseline value and∕or heart rate >90 bpm within 5 min after intubation. The ED50 and 95% confidence interval of sufentanil blunting the re?sponses to double?lumen endotracheal intubation were calculated using probit method. Results The ED50 ( 95% confidence interval) of sufentanil blunting the responses to double?lumen endotracheal intubation was 0?464 (0?309-0?580) μg∕kg. Conclusion When combined with propofol, the ED50 of sufentanil blun?ting the responses to double?lumen endotracheal intubation is 0?464 μg∕kg.

Objective To determine the effective dose 50 (ED50) of sufentanil blunting the responses to double-lumen endotracheal intubation under propofol in elderly patients.Methods A retrospective analysis was conducted on patients aged 65-78 years with body mass index＜30 kg/m2 , American Society of Anesthesiologists (ASA) I or Ⅱ and Mallampati grade Ⅰ or Ⅱ who underwent onelung ventilation under general anesthesia.Induction of anesthesia was initiated with sufentanil.Then propofol was administered to maintain a bispectral index (BIS) value ranging between 45 and 55.When the patients lost consciousness, cisatracurium 0.30 mg/kg was administrated, followed by double lumen endotracheal intubation.The dose of sufentanil was determined by the up and down sequential test.The initial dose was 0.50 μg/kg and the difference between two successive doses was 0.10 μg/kg.Responses to double-lumen endotracheal intubation were defined as the increase in invasive systolic blood pressure≥20％ of the baseline values and/or heart rate ＞90 bpm within 3 min after tracheal intubation.The ED50 (95％ confidence interval) of sufentanil blunting the responses to double-lumen endotracheal intubation was calculated.Results The ED50 (95％confidence interval) of sufentanil blunting the responses to double-lumen endotracheal intubation in elderly patients was 0.331 μg/kg, and the 95％ confidence interval was 0.246-0.409 μg/kg.Conclusions Under propofol to maintain BIS 45 55, the ED50 of sufentanil blunting the responses to double-lumen endotracheal intubation in elderly patients was 0.331 μg/kg.