The effect of dexmedetomidine pretreatment on the median effective bolus dose of propofol for facilitating laryngeal mask airway insertion.

Abstract

We designed this study to investigate the effect of dexmedetomidine (1μg/kg) pretreatment on the median effective dose (ED50) of propofol for facilitating successful laryngeal mask airway (LMA) insertion compared to propofol alone. Forty patients were randomized to either the control group (n=21) or the dexmedetomidine group (n=19). After infusion of normal saline or dexmedetomidine 1µg/kg over 10min, 1% lidocaine 0.5mg/kg, followed by propofol 2.5mg/kg was administered and the laryngeal mask airway was inserted without muscle relaxants. The ED50 of propofol for successful LMA insertion was determined by the modified Dixon's up-and-down method. The ED50 and ED95 were also calculated using an isotonic regression method, based on the pooled adjacent-violators algorithm-adjusted response rate, and the confidential interval (CI) was estimated using a bootstrap approach. The ED50 of propofol for smooth insertion of the LMA was significantly higher in the control group than in the dexmedetomidine group (3.1±0.4 vs 1.9±0.3mg/kg, P<0.001). From isotonic regression analysis using a bootstrap approach, the ED50 and ED95 of propofol was 2.9mg/kg (83% CI 2.5-3.3mg/kg) and 3.9mg/kg (95% CI 3.5-4.0mg/kg) in the control group, and 1.8mg/kg (83% CI 1.8-2.1mg/kg) and 2.4mg/kg (95% CI 2.0-2.5mg/kg) in the dexmedetomidine groups, respectively. The apnea time was not significantly different between the two groups. Pretreatment with dexmedetomidine 1μg/kg could reduce the propofol requirement by 38% for facilitating LMA insertion without prolonged respiratory depression and hemodynamic instability.