Perioperative plasma lidocaine concentrations and their impact on pain control. A systematic review and meta-analysis.

AIM: To review the relationship between drug concentrations of perioperative intravenous lidocaine and their analgesic effects. METHODS: We systematically searched SCOPUS, Medline, EMBASE, CENTRAL, and Web of Science (inception to March 2024) for randomized controlled trials comparing intraoperative lidocaine to placebo or control in adults undergoing non-cardiac surgery. Studies reported pain outcomes and plasma lidocaine concentrations. Bias was assessed using the Cochrane risk-of-bias tool, and data was analyzed with a random-effects model to determine mean difference (MD) and 95% confidence intervals (CI). RESULTS: Fifteen studies (445 lidocaine, 453 control patients) were included. Lidocaine lowered post-anesthetic care unit (PACU) opioid use (8 studies, MD: -3.00, 95% CI [-5.00, -1.01], p = 0.0092, I2 = 57%), with meta-regression indicating greater reduction at higher plasma concentrations (regression coefficient: -3.05, 95% CI [-4.48, -1.61], p = 0.002). However, 11 studies found no significant difference in 24-hour postoperative opioid consumption or pain scores. Nausea and vomiting incidence were similar between groups, and a few patients experienced lidocaine-related adverse events. CONCLUSION: Perioperative lidocaine infusion reduces PACU opioid consumption, with greater effects at higher concentrations, although significant heterogeneity was noted. Further research is needed to identify optimal concentrations for clinically significant analgesic benefits. PROTOCOL REGISTRATION: International Platform of Registered Systematic Review and Meta-analysis Protocols (INPLASY) ID: INPLASY202180046, DOI: 10.37766/inplasy2021.8.0046.