• Xiao-Ming Deng, Wen-Jing Xiao, Geng-Zhi Tang, Mao-Ping Luo, and Kun-Ling Xu.
• Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China 100041.
• Anesth. Analg. 2002 Jun 1;94(6):1465-8, table of contents.

UnlabelledRopivacaine is a new long-acting amino-amide local anesthetic. The concentrations of ropivacaine used in caudal analgesia range from 0.1% to 0.5%. The purpose of this study was to determine the minimum local analgesic concentration of ropivacaine to provide caudal analgesia in children. In a prospective, randomized, double-blinded clinical study, we studied 26 ASA grade I patients aged 1 to 5 yr who were scheduled for hypospadias operation under general anesthesia with caudal ropivacaine analgesia. General anesthesia was maintained with an end-tidal enflurane concentration of 0.8% in 100% oxygen (0.5 minimum alveolar anesthetic concentration [MAC]). Each child received 1 mL/kg of ropivacaine solution through a caudal catheter. The first child received ropivacaine 0.2%, and subsequent concentrations were determined by the analgesic response of the previous patient to the initial skin incision by use of Dixon's up-and-down sequential allocation. The testing interval was set at 0.025%. The minimum local analgesic concentration of ropivacaine for caudal analgesia under general anesthesia with 0.5 MAC enflurane was 0.11% (95% confidence interval [CI], 0.09%-0.12%), and the 95% effective concentration was 0.13% (95% CI, 0.12%-0.21%). In conclusion, the minimum local analgesic concentration of ropivacaine to provide effective caudal analgesia in children under general anesthesia with 0.5 MAC enflurane was found to be 0.11% (95% CI, 0.09%-0.12%).ImplicationsRopivacaine is a new long-acting amino-amide local anesthetic. The concentrations of ropivacaine used in caudal analgesia ranged from 0.1% to 0.5%. This study determined the minimum local analgesic concentration of ropivacaine to establish effective caudal analgesia under general anesthesia with 0.5 minimum alveolar anesthetic concentration enflurane in children.

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