Median effective target effect-site concentration of sufentanil inhibiting responses to insertion of laryngeal mask airway when combined with propofol in elderly patients

Abstract

Objective To determine the median effective target effect-site concentration (EC50) of sufentanil inhibiting responses to insertion of laryngeal mask airway (LMA) when combined with propofol in the elderly patients.Methods ASA physical status Ⅰ or Ⅱ patients,aged 66-75 yr,with body mass index of 19-30 kg/m2,scheduled for elective transurethral resection of prostate under general anesthesia,were included in this study.Anesthesia was induced with propofol given by target-controlled infusion.The initial target effect-site concentration (Ce) of propofol was 1 μg/ml,and the Ce was increased by 0.5 μg/ml every 1 min until it was increased to 2 μg/ml and maintained at this level for 5 min.Sufentanil was simultaneously administered by target-controlled infusion.The target Ce of sufentanil was 0.3 ng/ml in the first patient.The concentration of sufentanil was determined using the modified Dixon's up-and-down method.After the patients lost consciousness,LMA was inserted after the target effect-site and plasma concentrations were balanced.The insertion response was defined as positive when MAP and HR increased by 20％ of the baseline value within 5 min after insertion of LMA.The Ce of sufentanil was increased/decreased in the next patient if the insertion response was positive or negative.The ratio between the two successive concentrations was 1.2.The EC50 and 95 ％ confidence interval of sufentanil blunting responses to insertion of LMA was calculated using Probit analysis.Results When combined with propofol,the EC50 (95％ confidence interval) of sufentanil blunting responses to insertion of LMA was 0.160 (0.130-0.188) ng/ml.Conclusion The EC50 of sufentanil inhibiting responses to insertion of LMA is 0.160 ng/ml when combined with propofol in the elderly patients. Key words: Sufentanil ; Propofol ; Aged ; Dose-response relationship, drug