Low and High Doses of Caudal Morphine on Quality of Postoperative Analgesia and Morphine-Related Side Effects in Pediatric Urethroplasty: a Randomized Controlled Trial

Abstract

Background: Urethroplasty or surgical reconstruction of urethra which is usually recommended treatment of abnormal urethral opening such as hypospadias. General anesthesia combined with caudal epidural block is the commonly used anesthetic technique for this type of surgery. The dose range of caudal epidural morphine is variable from 30 to 50 mcg/kg depended on severity of surgical pain. Both analgesic efficacy and adverse effects of morphine including pruritus, nausea/vomiting and respiratory depression are dose-related. The aim of our study is to compare the analgesic efficacy and complications of caudal morphine between low dose (30 mcg/kg) and high dose (50 mcg/kg) for urethroplasty in children. Methods: Thirty-six children, aged 1–7 years, ASA physical status I or II, who were scheduled to undergo elective urethroplasty, were enrolled and randomly divided into two groups which were low-dose (30 mcg/kg) and high-dose (50 mcg/kg) groups. The primary outcome was the FLACC Behavioral Pain Assessment score at 6 h after operation. The secondary outcomes included postoperative FLACC Behavioral Pain Assessment score at 0, 1, 2, 4, 12, and 24 h, dose of rescue analgesics, analgesic duration, incidence of adverse effects of morphine and parent’s satisfaction. Results: There were no statistical differences in postoperative pain score, overall use of rescue analgesics, analgesic duration and parent’s satisfaction between the two groups. However, the requirement of rescue analgesics was higher in low-dose group compared with high-dose group (P=0.180). Moreover, patients in high-dose group had higher incidence of adverse events than patients in low-dose group but the difference did not reach the statistical significance. The common side effects were nausea, vomiting and pruritus. None developed respiratory depression. Conclusion: Our data shown that low dose (30 mcg/kg) of caudal epidural morphine has no statistically significant difference in postoperative analgesia and adverse effects compared to high dose (50 mcg/kg) caudal epidural morphine in pediatric urethroplasty procedure