The median effective dose, ED₅₀, of rocuronium bromide for inserting the laryngeal mask airway (LMA) in children was not known. The purpose of this study was to determine the clinical ED₅₀ (cED₅₀: median value of rocuronium dose of 6 set of crossing success and failure by Dixon's up-and-down method) of rocuronium to insert a LMA in pediatric patients.

Children aged 2 to 12 years (n = 21) and scheduled for urologic, orthopedic, plastic or ophthalmic surgery lasting less than 2 hr under general anesthesia were enrolled in this study. After applying a standard cardiorespiratory monitor, all patients received thiopental sodium 5 mg/kg for induction of anesthesia. Insertion of LMA was attempted 90 seconds after administration of rocuronium and manual ventilation with 8 vol% of sevoflurane. We recorded the movement of patients, blood pressure and heart rate. The initial dose of rocuronium was 0.3 mg/kg, and in accordance with Dixon's up-and-down method, the rocuronium concentration for consecutive patients in each patient was varied with increments or decrements of 0.05 mg/kg based on the result of previous patient.

The cED₅₀ of rocuronium required to insert a LMA was 0.09 mg/kg with 8 vol% sevoflurane. With isotonic regression, cED₉₅ of rocuronium was 0.13 mg/kg (95% confidence intervals 0.096-0.14 mg/kg).

This study demonstrated that the cED₅₀ and cED₉₅ of rocuronium were 0.09 mg/kg and 0.13 mg/kg in children respectively. It provides satisfactory conditions for LMA insertion in anesthetized children and decreases the excessive hemodynamic change.