Sevoflurane EC50 and EC95 values for laryngeal mask insertion and trachealintubation in children

The laryngeal mask airway (LMA(dagger)) is a simple, easy to use and safe m ethod for airway control in children. Its insertion needs less anaesthetic, and haemodynamic responses and postoperative sequelae are less than with l aryngoscopy and tracheal intubation. This study was designed to determine t he end-tidal concentrations of sevoflurane where 50% (EC50) and 95% (EC95) of the attempts to secure the airway would be successful. We randomly assig ned 40 children aged 4-12 yr undergoing general surgery to either LMA inser tion (n=20) or to laryngoscopy and tracheal intubation (n=20) under sevoflu rane anaesthesia. The initial end-tidal concentration of sevoflurane for ea ch 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 s evoflurane end-tidal concentrations in 0.3% steps were allowed for each chi ld. The logistic regression model was used to calculate the EC50 and EC95 v alues. Sevoflurane provided good conditions for both LMA insertion, and lar yngoscopy 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 inserti on 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 l aryngoscopy and tracheal intubation.