The dose of caudal epidural analgesia and duration of postoperative analgesia

Background: Single dose caudal epidural is commonly utilized for postoperative analgesia in children. Previous studies have determined the optimal concentration of local anaesthetic, and the minimal volume to produce a desired dermatomal distribution. However, none has sought the optimal volume to administer. The specific aim of this study was to determine whether the volume of caudal epidural local anaesthetic influenced the duration of postoperative analgesia. Methods: Fifty-four children aged 1-6 years and ASAPS I-II scheduled for elective inguinal herniorraphy were enrolled in this randomized and blinded clinical trial. They received a standardized general anaesthetic with one of three possible doses of caudal epidural analgesic: 0.7, 1.0, or 1.3 ml.kg^-1 of 0.175% bupivacaine with 1: 200 000 epinephrine. The patients were assessed by blinded observers during in-hospital recovery and by parents at home. Results: The principal outcome measure of time until first postoperative analgesic requirement was similar between the groups (4.2, 3.6, and 4.8 h respectively). Other effects which might be altered by epidural analgesia, including time until first void, ambulation, and discharge readiness did not differ between groups. Conclusions: Increasing local anaesthetic dose and volume do not increase the duration of postoperative analgesia of caudal epidural in children undergoing inguinal herniorraphy.