EC_(50) of ropivacaine for epidural anesthesia in hypospadias repair in children

Objective To determine EC50 of ropivacaine for epidural anesthesia in hypospadias repair in children. Methods Sequential trial was conducted in 23 children aged 12 to 36 months scheduled for hypospadias repair under epidural anesthesia. The initial concentration of ropivacaine was 0.4%, with a total dose of 1 ～ 1.5 mL/kg. If the efficacy of analgesia was ideal, a lower concentration of ropivacaine was administered to the next child; if not, but analgesia was improved by lidocaine of 1.2%, the next child received ropivacaine of a higher concentration. The concentration of ropivacaine would not changed if analgesia was not ideal and not improved by lidocaine. The concentration was increased or decreased sequentially in a ratio of 1.4 based on the analgetic effect on the prior child. Results Among the 23 children, three were excluded from this study because of uncertain efficacy. The results showed that EC50 of ropivacaine for epidural anesthesia in the childaren was 0.168% (95% CI 0.163% ～ 0.175%). Conclusions EC50 of ropivacaine for epidural anesthesia in hypospadias repair in children is 0.168% on the sequential trial.