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

Objective To determine the median effective effect-site concentration （EC50 ） of remifentanil inhibiting responses to laryngeal mask airway insertion when combined with propofol in elderly male patients . Methods Thirty ASA physical status Ⅰ or Ⅱ male patients ,aged 65〉yr ,with body mass index 〈30 kg/m2 , scheduled for elective transurethral resection of bladder tumor or prostate under general anesthesia ,were enrolled in this study .Anesthesia was induced with target-controlled infusion of propofol with a target plasma concentration （Cp） of 3 μg/ml .When Observer′s Assessment of Alertness/Sedation （OAA/S ） score ≤1 ,remifentanil target-controlled infusion was started with the initial target Cp set at 4.0 ng/ml . The concentration of propofol was adjusted until BIS value reached 55-65 ,and then the laryngeal mask airway was inserted .Modified Dixon’s up-and-down method was used to determine the Cp of remifentanil . Each time the Cp of remifentanil increased/decreased in the next patient depending on whether or not the response to laryngeal mask airway insertion occurred . The ratio of the two successive Cps was 1.2 .The response to laryngeal mask airway insertion was defined as development of coughing ,laryngospasm and/or body movement during insertion or within 3 min after insertion .The number of patients in whom inhibition of responses to insertion was effective/ineffective was recorded .The EC50 of remifentanil required to inhibit responses to laryngeal mask airway insertion and the 95% confidence interval when combined with propofol were calculated .Results The EC50 （95% confidence interval ） of remifentanil required to inhibit responses to laryngeal mask airway insertion was 1.86 （1.64-2.12） ng/ml when combined with propofol in elderly male patients .Conclusion The EC50 of remifentanil required to inhibit responses to laryngeal mask airway insertion is 1.86 ng/ml when combined with propofol in elderly male patients . Key words: Piperidines; Propofol; Aged; Laryngeal mask; Dose-response relationship,drugs