Ropivacaine Pediatric Caudal Block Of The Minimum Effective Analgesic Concentration And Its Clinical Application

The First Part: The minimum Local Analgesic Concentrations of Ropivacaine for Caudal Block in Pre-school and School Aged ChildrenObjective:This prospective randomized, controlled and double blinded clinical study will use the method of Dixon's up-and-down to determine the MLAC of ropivacaine to establish caudal analgesia with light general anesthesia in pre-school and school aged children undergoing hypospadias repair.Methods:We studied 51 boys, ASA â…  , aged 1 ¹2. yr old, undergoing hypospadias repair surgery under general anesthesia with caudal analgesia. Children were allocated randomly into preschool-aged group (aged 1⁵ yr) and school-aged group (aged 6¹2 yr) . Anesthesia was induced via face mask with enflurane and 60% N₂O in oxygen. After placement of an iv cannula, propofol 2 mg/kg and succinylcholine 1 mg/kg were given to facilitate orotracheal intubation. All children were allowed to breath spontaneously and an end-tidal enflurane concentration of 0.8% in 100% oxygen was maintained before incision. After the anesthesia induction, the children were placed in the left lateral position, and caudal block was performed with a 22-gauge iv catheter. Each child received ropivacaine 1 ml/kg of the desired concentration. The first child in each group 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 Dixion's up-and-down sequential allocation. The testing interval concentration was set at 0.025%.Results:The MLAC of ropivacaine for caudal block under general anesthesia with 0.8% end-tidal enflurane in pre-school aged children was 0.105% (95%CI, 0.086%⁰.123%), and EC95 was 0.134% (95%CI, 0.118%⁰.241%) . The MLAC in school aged children was 0.158% (95%CI 0.141%⁰.175%), and EC₉₅ was 0.191% (95%CI, 0.175% 0.281%) . The MLAC in school aged children was 51% (95%CI, 36%⁶6%) higher than that in pre-school aged children.Conclusions:The MLAC of ropivacaine for caudal block in school-aged children was 51% higher...