End-tidal concentrations of sevoflurane and desflurane for ProSeal laryngeal mask airway removal in anaesthetised adults A randomised double-blind study

BACKGROUND The optimal end-tidal sevoflurane and desflurane concentration for successful ProSeal laryngeal mask airway (PLMA) removal in unpremedicated anaesthetised adults has not been determined. OBJECTIVES We determined end-tidal sevoflurane and desflurane concentration in 50% of anaesthetised adults (EC50: concentration at which there is 50% chance of patients showing 'no movement' response) for smooth PLMA removal. DESIGN Randomised controlled double blind study. SETTING Operating theatre of a government tertiary care institute. The study period was December 2011 to January 2013. PATIENTS Thirty nine unpremedicated American Society of Anesthesiologists (ASA) physical status I and II women with cervical carcinoma (aged 30 to 60 years) scheduled for implantation of intracavity caesium under general anaesthesia with PLMA as an airway device were included in the study. INTERVENTIONS The participants were randomised to one of the two groups receiving either desflurane or sevoflurane for anaesthesia maintenance. Anaesthesia induction was performed with intravenous propofol. Predetermined end-tidal sevoflurane concentration (initiating at 2%) or desflurane (initiating at 4%) was sustained for 10 min before PLMA removal was attempted. End-tidal concentrations were increased/decreased (step-size 0.2% for sevoflurane and 0.5% for desflurane) using Dixon and Massey up and down method in the next patient depending upon previous patient's response. Patient responses to PLMA removal were classified as 'movement' or 'no movement'. MAIN OUTCOME MEASURES EC50 was calculated as the mean of the crossover pairs' midpoints in each group and further confirmed by probit regression analysis. RESULTS EC50 (95% confidence interval) of sevoflurane and desflurane for PLMA removal were 1.58% (0.669 to 2.060) and 2.79% (2.733 to 2.841), respectively. CONCLUSION Predicted EC50 and EC95 of sevoflurane and desflurane for smooth removal for the PLMA were 1.58 (0.669 to 2.060), 2.27 (1.859 to 21.16), 2.79 (2.733.2.841) and 3.27% (3.173 to 3.395), respectively. TRIAL REGISTRATION Registered with Clinical Trial Registry of India (URL: http://www.ctri.in), Registry ref no: CTRI/2012/12/004285.