Fentanyl versus remifentanil-based TIVA for pediatric scoliosis repair: does it matter?

Opioid-induced hyperalgesia (OIH) and acute opioid tolerance have been demonstrated extensively in patients undergoing adolescent idiopathic scoliosis (AIS) repair. Remifentanil infusion has been strongly linked to both tolerance and OIH in these patients; however, the impact of using an intraoperative fentanyl infusion has not been well studied. This study aims to determine if patients undergoing operative management of AIS have decreased opioid consumption and pain scores when an intraoperative fentanyl infusion is used as compared with a remifentanil infusion.

This is a retrospective chart review of patients with AIS who underwent posterior spinal fusion. During the period January 2012-June 2013, patients received remifentanil infusion as part of total intravenous anesthesia. From July 2013 to June 2015, remifentanil was replaced by fentanyl as standard protocol. The remifentanil cohort included 37 patients and the fentanyl cohort included 25 patients. The primary outcome was the total opioid consumption (morphine equivalents) in the first 24 hours postsurgery. Secondary outcomes included mean postoperative pain score in the first 24 hours postsurgery, postoperative opioid consumption 24-48 hours after surgery, time to extubation, time to assisted ambulation, length of stay, and incidence of postoperative nausea and vomiting.

Compared with the remifentanil group, the fentanyl group had significantly higher postoperative opioid usage during the first 48 hours and significantly higher postoperative mean pain score during the first 24 hours. There was no difference between the two groups in mean pain score for 24-48 hours, extubation time, time to assisted ambulation, length of stay, or postoperative nausea and vomiting.

Despite concerns for hyperalgesia and acute tolerance, remifentanil is widely used for intraoperative opioid infusions for surgical correction of AIS. This retrospective study examined a practice change from intraoperative remifentanil to intraoperative fentanyl as a potential approach to avoid OIH. Surprisingly, patients receiving fentanyl intraoperatively showed increased postoperative opioid use and pain scores in the first 24 hours postsurgery compared with the prior cohort receiving remifentanil. Substitution of fentanyl for remifentanil during surgical correction of AIS does not appear to solve the problem of OIH or acute tolerance. Prospective studies are needed to confirm this unexpected result.