Optimal pain relief in day-case surgery is imperative to patient comfort and timely discharge from hospital. Short-acting opioids are commonly used for analgesia in modern anaesthesia, allowing rapid recovery after surgery. Plasma concentration fluctuations from repeated dosing of short-acting opioids can cause patients to oscillate between analgesia with potential adverse effects, and inadequate analgesia requiring rescue dosing. Methadone's unique pharmacology may offer effective and sustained analgesia with less opioid consumption, potentially reducing adverse effects. Using a double-blind, randomised controlled trial, we compared post-anaesthesia care unit opioid consumption between day-case gynaecological laparoscopy patients who received either intravenous methadone (10 mg), or short-acting opioids intraoperatively. The primary outcome was post-anaesthesia care unit opioid consumption in oral morphine equivalents. Secondary outcomes included total opioid consumption, discharge opioid consumption, pain scores (0-10) until discharge, adverse effects (respiratory depression, postoperative nausea and vomiting, excess sedation), and rate of admission. Seventy patients were randomly assigned. Patients who received methadone consumed on average 9.44 mg fewer oral morphine equivalents in the post-anaesthesia care unit than the short-acting group (18.02 mg vs 27.46 mg, respectively, 95% confidence interval 0.003 to 18.88, P = 0.050) and experienced lower postoperative pain scores at every time point, although absolute differences were small. There was no evidence of lower hospital or discharge opioid consumption. No significant differences between the methadone and short-acting groups in other outcomes were identified: respiratory depression 41.2% versus 31.4%, Padjusted >0.99; postoperative nausea and vomiting 29.4% versus 42.9%, Padjusted >0.99; overnight admission 17.7% versus 11.4%, Padjusted >0.99; excess sedation 8.82% versus 8.57%, Padjusted >0.99. This study provides evidence that, although modestly, methadone can reduce post-anaesthesia care unit opioid consumption and postoperative pain scores after day-case gynaecological laparoscopy. There were no significant differences in any secondary outcomes.
Keywords: Pain management; adult anaesthesia; anaesthetics; gynaecological surgery; methadone; minimally invasive surgery; opioid analgesia; opioid-sparing; perioperative care; postoperative pain management.