Sevoflurane EC50 and EC95 values for laryngeal mask insertion and tracheal intubation in children.

The laryngeal mask airway (LMA) is a simple, easy to use and safe method for airway control in children. Its insertion needs less anaesthetic, and haemodynamic responses and postoperative sequelae are less than with laryngoscopy and tracheal intubation. This study was designed to determine the end-tidal concentrations of sevoflurane where 50% (EC50) and 95% (EC95) of the attempts to secure the airway would be successful. We randomly assigned 40 children aged 4-12 yr undergoing general surgery to either LMA insertion (n=20) or to laryngoscopy and tracheal intubation (n=20) under sevoflurane anaesthesia. The initial end-tidal concentration of sevoflurane for each child was determined according to the response of the previous child in the same group. Up to three attempts to secure the airway with increasing sevoflurane end-tidal concentrations in 0.3% steps were allowed for each child. The logistic regression model was used to calculate the EC50 and EC95 values. Sevoflurane provided good conditions for both LMA insertion, and laryngoscopy and tracheal intubation without serious adverse effects. The EC50 and the EC95 of sevoflurane were 1.57 (SD 0.33)% and 2.22% for LMA insertion and 2.20 (SD 0.31)% and 2.62% for laryngoscopy and tracheal intubation. Thus, less sevoflurane is required for LMA insertion in children than for laryngoscopy and tracheal intubation.