Sevoflurane EC_(50) and EC_(95) Values for the Removal of the Laryngeal Mask Airway in Children

Objective To determine the concentrations of sevoflurane where 50%(EC50) and 95%(EC95) of the attempts to remove the laryngeal mask airway(LMA) would be successful in children.MethodsTwenty-five nonpremedicated children,aged 3-6 years,ASA physical status I,scheduled for inguinal herniorrhaphy were enrolled in this study.General anesthesia was induced and maintained with sevoflurane and 50%nitrous oxide in oxygen.After the surgery,the target concentration was maintained for at least 15 min,and then the LMA was removed.Each target concentration was predetermined by the Dixon's up-and-down method(with 0.1% as a step size) starting at 1.70% concentration of sevoflurane.A removal accomplished without coughing,teeth clenching,gross purposeful movement,breath holding or laryngospasm,during or within 1 min after removal was considered to be successful.ResultsThe concentration of sevoflurane to achieve successful LMA removal in 50% of children was 1.49%(95%CL,1.37%-1.59%) and in 95% of children was 1.70%(95%CL,1.59%-2.84%).ConclusionThe EC50 and EC95 values of sevoflurane for LMA smooth extubation in children aged 3~6 years were 1.49% and 1.70%,respectively.