Analgesic effects of methadone and magnesium following posterior spinal fusion for idiopathic scoliosis in adolescents: a randomized controlled trial.

Purpose: To provide optimal conditions for neurophysiological monitoring and rapid awakening, remifentanil is commonly used during pediatric spinal surgery. However, remifentanil may induce hyperalgesia and increase postoperative opioid requirements. We evaluated the potential of methadone or magnesium to prevent remifentanil-induced hyperalgesia.

Methods: Using a prospective, randomized, blinded design, adolescents presenting for posterior spinal fusion to treat idiopathic scoliosis were assigned to receive desflurane with remifentanil alone (REMI), remifentanil + methadone (MET) (0.1 mg/kg IV over 15 min), or remifentanil + magnesium (MAG) (50 mg/kg bolus over 30 min followed by 10 mg/kg/h). Primary outcomes were opioid requirements and postoperative pain scores. Secondary outcomes included intraoperative anesthetic requirements, neurophysiological monitoring conditions, and emergence times.

Results: Data analysis included 60 patients. Total opioid requirement (hydromorphone) in the REMI group (received perioperatively and on the inpatient ward) was 0.34 ± 0.11 mg/kg compared to 0.26 ± 0.10 mg/kg in the MET group (95% confidence interval (CI) of difference: - 0.14, - 0.01; p = 0.035). The difference in opioid requirements between the REMI and MET group was related to intraoperative dosing (0.04 ± 0.02 mg/kg vs. 0.02 ± 0.01 mg/kg; 95% CI of difference: - 0.01, - 0.02; p = 0.003). No difference was noted in pain scores, and no differences were noted when comparing the REMI and MAG groups.

Conclusion: With the dosing regimens in the current study, the only benefit noted with methadone was a decrease in perioperative opioid requirements. However, given the potential for hyperalgesia with the intraoperative use of remifentanil, adjunctive use of methadone appears warranted.