Opioid-Free Anaesthesia Improves Anaesthesia Recovery when Compared with that of Opioid-Based Anaesthesia. Systematic Review and Meta-Analysis of Clinical Trials

Introduction: Opioid free anesthesia (OFA) is a relatively new technique that has been questioned due to the lack of evidence regarding its benefit-risk balance. Methods: Four international databases were searched for clinical trials comparing OFA with opioid based anesthesia. The primary outcome was pain control and the secondary included postoperative nausea and vomiting (PONV), gastrointestinal recovery, respiratory depression, urinary retention, length of hospital stay, surgical complications, number of patients with cessation of the intervention and other side effects. Results: Pain was better controlled in the OFA group in all the measurements made (VAS 1h: Md= -0.81, CI95%= -0.48- -1.14, VAS 24h: Md= -1.25,CI95%=-2.41- -0.1, VAS >24h: Md= -1.36, CI95%= -1.73- -1). In the opioid group there was an increase in the risk of nausea (RR=2.69, CI95%=2-3.61) and vomiting (RR= 3.99, CI95%=2.06-7.74), whilst in the OFA group, there was an increased risk of bradycardia (RR=1.62, CI95%=1.02-2.57). The rest of the variables showed no differences between groups or could not be analyzed. Conclusion: There is a clear benefit of OFA in pain control and PONV, but there is also a higher risk of bradycardia. This technique should be considered in patients with a special risk of difficult postoperative pain control or PONV. However, the best drug combination to perform OFA is still unknown, as well as the type of patient that benefits more with less risk.