Context: The single-use Laryngeal Mask Airway (LMA) Supreme is a new supraglottic airway device. It has been reported to be reliable and easy-to-use in clinical practice; however, the anaesthetic techniques for its insertion are not standardised.
Objectives: The purpose of this study was to determine the ED50 of end-tidal sevoflurane concentration for successful LMA Supreme insertion without the use of neuromuscular blockade.
Design: A prospective observational study.
Setting: A single tertiary care surgical centre.
Patients: Thirty-one consecutive elective patients scheduled for minor elective surgery under general anaesthesia.
Intervention: Patients were preoxygenated with 100% oxygen and anaesthetised using normal tidal volume inhalation of sevoflurane. The target sevoflurane concentration was determined using a modified Dixon's 'up-and-down' method (starting at 2.5% with 0.5% as the step size). After the predetermined end-tidal concentration had been established and maintained for 10 min, LMA Supreme insertion was attempted.
Main outcome measure: The main outcome measure was the patient's response to LMA Supreme insertion, classified as either 'movement' or 'no movement'. The mean of the concentrations of seven cross-overs from 'movement' to 'no movement' was used to estimate the ED50.
Results: The estimated sevoflurane concentration for successful LMA Supreme insertion in 50% of adults was 3.03 ± 0.75% (95% confidence interval 2.3 to 3.7%). The values of the ET50 and ET95 obtained by logistic regression were 2.83 and 5.30%, respectively.
Conclusion: Sevoflurane alone can provide acceptable conditions for insertion of the LMA Supreme in adults, at an estimated minimum alveolar anaesthetic concentration of 3% with minimal adverse effects.