Dose-response relationship of alfentanil in combination with midazolam-etomidate inhibiting cardiovascular responses to laryngeal mask airway implantation in elderly patients / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the dose-response relationship of alfentanil in combination with midazolam-etomidate inhibiting cardiovascular responses to laryngeal mask airway implantation in elderly patients.Methods:American Society of Anesthesiologists Physical Status Ⅰ or Ⅱ patients of either sex, aged 65-85 yr, with body mass index of 20-30 kg/m 2, undergoing elective operation under general anesthesia, were enrolled in this study.Midazolam 0.025 mg/kg was intravenously injected for adequate sedation, 5 min later mean arterial pressure and heart rate were recorded for 3 consecutive times at 3-min interval, the mean value was collected and considered as the baseline value.Etomidate 0.2 mg/kg was intravenously injected, and alfentanil and rocuronium 0.6 mg/kg were intravenously injected when bispectral index value < 60.A laryngeal mask airway was inserted at 1.4 min after intravenous injection of alfentanil, and mechanical ventilation was performed.The dose of alfentanil was determined by the Dixon′s up-and-down method.The initial dose of alfentanil was set at 6.83 μg/kg.The dose of alfentanil in the next patient was determined according to the development of cardiovascular response to laryngeal mask airway placement.If the cardiovascular response to laryngeal mask airway placement occurred, the dose was increased for the next patient, and if cardiovascular response to laryngeal mask airway placement did not occur, the dose was decreased, and the ratio between the two successive doses was 1.0∶1.1.The cardiovascular response to laryngeal mask airway placement was defined as increase in maximum mean arterial pressure or maximum heart rate by≥20% of baseline values within 2 min after laryngeal mask airway placement.The median effective dose (ED 50), 95% effective dose (ED 95) and 95% confidence interval (95% CI) of alfentanil inhibiting cardiovascular responses to laryngeal mask airway placement in elderly patients were calculated by the Probit method. Results:When combined with midazolam and etomidate, the ED 50 (95% CI) of alfentanil inhibiting the cardiovascular responses to laryngeal mask airway placement in elderly patients were 5.605 (5.036-6.082) μg/kg, and the ED 95 (95% CI) were 6.625 (6.125-9.763) μg/kg. Conclusions:When combined with midazolam and etomidate, the ED 50 and ED 95 of alfentanil inhibiting the cardiovascular responses to laryngeal mask airway placement are 5.605 and 6.625 μg/kg, respectively, in elderly patients.