Male patients require higher optimal effect-site concentrations of propofol during i-gel insertion with dexmedetomidine 0.5 mu g/kg

Abstract

Background: The pharmacokinetics and pharmacodynamics of an anesthetic drug may be influenced by gender. The purpose of this study was to compare effect-site half maximal effective concentrations (EC50) of propofol in male and female patients during i-gel insertion with dexmedetomidine 0.5 mu g/kg without muscle relaxants. Methods: Forty patients, aged 20-46 years of ASA physical status I or II, were allocated to one of two groups by gender (20 patients per group). After the infusion of dexmedetomidine 0.5 mu g/kg over 2 min, anesthesia was induced with a pre-determined effect-site concentration of propofol by target controlled infusion. Effect-site EC50 values of propofol for successful i-gel insertion were determined using the modified Dixon's up-and-down method. Results: Mean effect-site EC50 +/- SD of propofol for successful i-gel insertion was significantly higher for men than women (5.46 +/- 0.26 mu g/ml vs. 3.82 +/- 0.34 mu g/ml, p < 0.01). The EC50 of propofol in men was approximately 40 % higher than in women. Using isotonic regression with a bootstrapping approach, the estimated EC50 (95 % confidence interval) of propofol was also higher in men [5.32 (4.45-6.20) mu g/ml vs. 3.75 (3.05-4.43) mu g/ml]. The estimated EC95 (95 % confidence interval) of propofol in men and women were 5.93 (4.72-6.88) mu g/ml and 4.52 (3.02-5.70) mu g/ml, respectively. Conclusions: During i-gel insertion with dexmedetomidine 0.5 mu g/kg without muscle relaxant, male patients had higher effect-site EC50 for propofol using Schnider's model. Based on the results of this study, patient gender should be considered when determining the optimal dose of propofol during supraglottic airway insertion.