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

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 μg/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 μg/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 μg/ml vs. 3.82 ± 0.34 μg/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) μg/ml vs. 3.75 (3.05–4.43) μg/ml]. The estimated EC95 (95 % confidence interval) of propofol in men and women were 5.93 (4.72–6.88) μg/ml and 4.52 (3.02–5.70) μg/ml, respectively. CONCLUSIONS: During i-gel insertion with dexmedetomidine 0.5 μg/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. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02268656. Registered August 26, 2014.