Intraoperative infusion of 0.6-0.9 µg·kg(-1)·min(-1) remifentanil induces acute tolerance in young children after laparoscopic ureteroneocystostomy.

BACKGROUND Intraoperative infusion of opioids has been associated with increased postoperative pain and analgesic requirements, but the development of tolerance in young children is less clear. This prospective, randomized, double-blinded study was designed to test the hypothesis that the intraoperative administration of remifentanil results in postoperative opioid tolerance in a dose-related manner in young children. METHODS We enrolled 60 children (aged 1-5 yr) who were undergoing elective laparoscopic ureteroneocystostomy. Patients were randomized and received an intraoperative infusion of 0, 0.3, 0.6, or 0.9 µg·kg·min remifentanil. Postoperative pain was managed by a parent/nurse-controlled analgesia pump using fentanyl. The primary outcome included the total fentanyl consumptions at 24 and 48 h postsurgery. Secondary outcomes were the postoperative pain scores and adverse effects. RESULTS The children who received 0.6 and 0.9 µg·kg·min remifentanil required more postoperative fentanyl than the children who received saline or 0.3 µg·kg·min remifentanil (all P < 0.001) for 24 h after surgery. The children who received 0.3-0.9 µg·kg·min intraoperative remifentanil reported higher pain scores at 1 h after surgery than the children who received saline (P = 0.002, P = 0.023, and P = 0.006, respectively). No significant intergroup differences in recovery variables were observed, but vomiting was more frequent in the 0.9 µg·kg·min remifentanil group than in the other groups (P = 0.027). CONCLUSIONS The intraoperative use of 0.3 µg·kg·min remifentanil for approximately 3 h (range: 140-265 min) did not induce acute tolerance, but the administration of 0.6 and 0.9 µg·kg·min remifentanil to young children resulted in acute tolerance for 24 h after surgery in an apparently dose-related manner.