Effect of Opioid-Free Anaesthesia on Perioperative Period: A Review

Introduction: Balanced anaesthesia relies on the administration of opioids in the perioperative period as antinociceptive agents. There is no clear evidence that intraoperative opioids result in reduction of postoperative pain scores. Opioid-free anaesthesia (OFA), combination of various opioids-sparing techniques leading to no administration of intraoperative systemic, neuraxial or intracavitary opioids, arises from the attempt to develop anti-hyperalgesic techniques to improve postoperative pain control. Therefore, the aim of this review is to understand to which extend is opioid free beneficial in the perioperative period, more specifically the analgesic impact of this technique. Methods: The electronic databases Medline and PubMed were searched until November 2019. We included meta-analyses, randomized controlled trials and prospective studies investigating pain outcomes comparing any type of intra-operative opioid general anaesthesia with opioid-free general anaesthesia. The primary outcome was first measure of pain score at rest and at 24 postoperative hours. Secondary outcomes included rescue analgesia, intravenous (i.v.) morphine consumption equivalents at 24h postoperatively, rates of postoperative nausea and vomiting (PONV) within the first 24 postoperative hours, rates of rescue antiemetic drugs, length of stay in post-anaesthesia care unit (PACU) and total hospital length of stay. Eleven studies were identified, three of which are meta-analysis. Results: Mean pain scores at rest in the first measure as well as at 24 postoperative hours were lower in the opioid free anaesthesia (OFA) group than in opioid based anaesthesia (OBA). Use of rescue postoperative analgesia and i.v. morphine consumption equivalents were lower in the OFA group. A statistically significant trend toward a decrease in PONV and use of antiemetic drugs among patients who did not received opioids was observed. Length of stay PACU was longer in the opioid free group, but only three of six trials reported a statistically significant difference. Finally, total length of stay in the hospital was investigated by two trials and was similar between groups. Conclusion: OFA, when compared with OBA, does not present inferior results regarding pain scores or opioid consumption in the postoperative period. It is also associated with reduced postoperative nausea and vomiting. The OFA technique presents as future challenges an objective documentation of both its short-term and long-term benefits and inconveniencies. Further research with robust methodological trials with large sample sizes are required to better determine the efficacy and safety of opioid-free anaesthetic strategy.