Optimum concentration of bupivacaine for combined caudal-general anesthesia in children

Abstract

Caudal epidural anesthesia has become widely accepted as a means of providing postoperative pain relief and intraoperative supplementation to general anesthesia for children. To determine the best concentration of bupivacaine for combined general-caudal anesthesia in children, 122 children aged 1-8 yr scheduled for outpatient inguinal herniorrhaphy were randomized to receive, in a double-blind fashion, caudal anesthesia with bupivacaine in one of six concentrations (0.125, 0.15, 0.175, 0.2, 0.225, or 0.25%). After incision, a programmed reduction in inspired halothane resulted, if tolerated by the subject, in an inspired halothane concentration of 0.5% 10 min after incision. End-tidal halothane concentration at hernia sac ligation for subjects receiving 0.175% bupivacaine (0.55 ± 0.03%) was less than that for subjects receiving 0.15% bupivacaine (0.75 ± 0.05%; P < 0.05). Subjects receiving 0.175% bupivacaine also were discharged earlier from the postanesthesia care unit (PACU) (27 ± 1 min) than were subjects receiving 0.15% bupivacaine (38 ± 5 min; P = 0.05). Children receiving ≥ 0.2% bupivacaine tended to complain more of leg weakness after surgery; however, the difference did not reach statistical significance (39 of 67 vs. 16 of 47; P = 0.057). The incidence of complaints of leg weakness and paresthesia was positively correlated with bupivacaine concentration (r = 0.706; P = 0.05). Subjects receiving 0.125% bupivacaine had higher pain scores on arrival to the PACU than did those receiving 0.2% bupivacaine (P = 0.05); there were no other differences in pain scores. Subjects receiving 0.175% bupivacaine ambulated sooner (129 ± 6 min) than did subjects receiving 0.125 and 0.2% bupivacaine (202 ± 20 min, 207 ± 21 min; P ≤ 0.01). Subjects receiving 0.175% bupivacaine also were discharged home sooner (167 ± 8 min) than were subjects receiving 0.125 and 0.15% bupivacaine (248 ± 26 min, 255 ± 40 min; P ≤ 0.05). Discharge home was delayed in subjects with ineffective intraoperative caudal supplementation (262 ± 27 min vs. 196 ± 8 min; P < 0.01) and in subjects who received supplemental analgesics (253 ± 16 min vs. 177 ± 17 min; P < 0.001). Although all concentrations were effective for combined general-caudal anesthesia in children, we conclude that 0.175% bupivacaine offers the best combination of effectiveness and rapid recovery and discharge for pediatric surgical outpatients.