Scheduled methadone reduces overall opioid requirements after pediatric posterior spinal fusion
A single center retrospective case series
November 2022 by Dr Bojana Stepanovic
- A retrospective chart review of 94 patients undergoing posterior spinal fusion for adolescent idiopathic scoliosis between 2015 and 2020 at the American Family Children’s Hospital, University of Wisconsin, USA.
- Three patient groups:
o Group PCA received a hydromorphone PCA without methadone
o Group PCA + Methadone received pre-incisional methadone and a hydromorphone PCA
o Group Methadone received pre-incisional methadone, scheduled postoperative methadone, and no PCA
- Methadone dosing:
o Pre-incisional methadone 0.2 mg/kg (max 20 mg)
o Post-operative methadone 0.1mg/kg (max 5 mg) IV in the PACU at first request for analgesia, and methadone 0.1 mg/kg (max 5 mg) IV 6 h after the PACU dose, with backup rescue hydromorphone IV boluses available on request.
- The primary outcome was postoperative opioid use over 72hrs. Secondary outcomes included pain scores, sedation scores and length of stay.
- Intraoperatively all patients received TIVA with remifentanil or fentanyl infusion and additional opioid boluses at the anaesthetist’s discretion.
- The study period included post-operative days 0-3.
- Group Methadone used significantly less opioid than Group PCA and Group PCA + Methadone
o Mean hydromorphone equivalents in mg/kg = 0.18 vs 0.33 and 0.30 respectively
- There were no statistically significant differences between the groups for secondary outcomes.
Intravenous methadone is a unique opioid that acts at multiple receptors, including mu-opioid, kappa- opioid, N- Methyl- D- aspartate (NMDA), serotonin, and norepinephrine. The clinical duration of action is dose-dependent and is significantly extended with repeat dosing. Methadone undergoes rapid redistribution after bolus administration and so supplementation of the pre-incisional dose with subsequent doses maintains analgesic plasma levels. Dose finding studies have found similar pharmacokinetics in adolescents and adults.
There was generally standardisation of care for spinal fusion patients with a streamlined multidisciplinary care pathway developed in 2015, which limits other confounding factors in post-operative care. All patients received standardised non opioid analgesia including gabapentin, acetaminophen and non-steroidal anti-inflammatories.
In terms of safety profile, none of the patients in the methadone groups experienced QT prolongation while on telemetry for the first 24 hrs post operatively.
This is a single centre retrospective chart review, so it is prone to bias and the numbers of patients in each group is small, with unequal patient sizes, and missing pain data points in all groups.
Total opioid was calculated incorporating methadone, hydromorphone, oxycodone and morphine doses and excluded short acting opioid doses of fentanyl, remifentanil, alfentanil and sufentanil.
There was a statistically significant difference in long-acting opioid use between all groups, however there was not a clinically significant difference between the PCA group and PCA + methadone group. This review suggests that the real opioid sparing benefit was gained by the scheduled methadone group receiving multiple doses of methadone.