Median effective dose of dezocine inhibiting responses to insertion of laryngeal mask airway when combined with propofol in elderly patients

Abstract

Objective To determine the median effective dose(ED50)of dezocine inhibiting responses to insertion of laryngeal mask airway(LMA)when combined with propofol in the elderly patients. Methods American Society of Anesthesiologists physical statusⅠorⅡ patients, aged 66-75 yr, with body mass index of 20-25 kg/m2, were included in this study.Anesthesia was induced with dezocine at the initial dose of 0.2 mg/kg and propofol which was simultaneously administered by target-controlled infusion.The initial target plasma concentration of propofol was 1 μg/ml, and the concentration was increased in increments of 0.5 μg/ml every 3 min until the target concentration 3 μg/ml was achieved.LMA was inserted when bispectral index value reached 50-60.The dose of dezocine was determined using the up-and-down method.The response to insertion of LMA was defined as positive when patients developed coughing, laryngospasm and/or body movement during insertion or within 3 min after insertion.The dose of dezocine was increased/decreased in the next patient if the insertion response was positive or negative.The ratio between the two successive doses was 0.8.The ED50 and 95% confidence interval of dezocine inhibiting responses to insertion of LMA were calculated. Results When combined with propofol, the ED50 of dezocine inhibiting responses to insertion of LMA was 0.126 mg/kg, and the 95% confidence interval was 0.110-0.143 mg/kg. Conclusion The ED50 of dezocine inhibiting responses to insertion of LMA is 0.126 mg/kg when combined with propofol in the elderly patients. Key words: Analgesics, opioid; Propofol; Aged; Dose-response relationship, drug; Laryngeal masks