Methadone for Spinal Fusion Surgery.

During early recovery after surgery, intravenous opioids are typically administered to control the pain, either as intermittent bolus administration by nursing staff or by a patient-controlled analgesia device. Unfortunately, repeated doses or boluses of shorter-acting opioids, such as morphine, oxycodone and fentanyl, result in fluctuating blood concentrations, with the inherent risk of only relatively brief periods of adequate pain relief. Moreover, the use of shorter-acting opioids increases the risk of opioid-associated side effects, such as sedation, nausea and vomiting. An alternative approach to the postoperative use of shorter-acting opioids is therefore called for. In this respect, methadone is an opioid with unique pharmacological properties that may be advantageous when applied intraoperatively. A single-dose of this long acting opioid could provide a stable analgesia and potentially reduce the need for shorter-acting opioids Method: 150 patients will be included in an investigator-initiated, prospective, randomised, double-blind, controlled trial with three arms: intervention arm 1 (methadone administered at induction 0.15-0.2 mg/kg ideal body weight), Intervention arm 2 (methadone administered in the end of surgery 0.15-0.2 mg/kg ideal body weight), Control arm (morphine administered in the end of surgery 0.15-0.2 mg/kg ideal body weight). The study will be GCP-monitored, and is approved by the Danish Health and Medicines Authority (2020103115) and the Central Denmark Region Committees on Health Research Ethics (1-10-72-278-20). Objective The aim of this study is to investigate the effect of a single dose of intravenous intraoperative methadone on postoperative opioid consumption, pain and side effects in patients scheduled for spinal fusion surgery. A single dose of intravenous intraoperative morphine will be used as an active comparator. Hypothesis * Intravenous perioperative methadone reduces opioid consumption (oral cumulative equivalent dose) by 50% during the first 24 postoperative hours compared to intravenous morphine(primary outcome). * Methadone reduces opioid consumption the first 6 postoperative hours compared to intravenous morphine * Methadone reduces pain in the affected areas at rest and during coughing(1-72 hours after extubation) compared to intravenous morphine * Methadone increases patient satisfaction with pain management during the first 24 postoperative hours compared to intravenous morphine on a Numerical Rating Scale (NRS) from 0 to 10, where 0 is unsatisfied and 10 is satisfied * The effects of methadone is attenuated when administered prior to surgical incision compared to administration in the end of surgery * The frequency of opioid-related side effects is similar in the groups compared.