Efficacy and safety of intravenous lidocaine in thyroidectomy: a systematic review and meta-analysis with trial sequential analysis and meta-regression

BACKGROUND: Thyroidectomy is a common surgical procedure associated with postoperative pain and postoperative nausea and vomiting (PONV), which may impair early recovery and quality of recovery (QoR). Intravenous (IV) lidocaine has been proposed as a component of multimodal analgesia; however, its efficacy and safety in patients undergoing thyroidectomy remain uncertain. Therefore, this systematic review and meta-analysis aimed to evaluate the efficacy and safety of perioperative IV lidocaine in this population. METHODS: Following PRISMA guidelines, a systematic search was conducted across PubMed, Scopus, Web of Science, and the Cochrane Library from inception to Aug 13 2025. Randomised controlled trials (RCTs) comparing IV lidocaine with placebo (normal saline) in adult patients undergoing thyroidectomy were included. The primary outcome was postoperative pain scores at 1, 4, 8, 12, 24, and 48 h. Secondary outcomes included quality of recovery (QoR) scores; incidence of postoperative nausea and vomiting (PONV); use of antiemetics; duration of anaesthesia; total postoperative opioid consumption; and postoperative analgesia use. Meta-analyses were performed using random-effects models. The Hartung-Knapp-Sidik-Jonkman (HKSJ) method was applied when moderate or substantial heterogeneity was present (I² > 40%), whereas the DerSimonian and Laird (DL) method was used when heterogeneity was low to moderate (I² ≤ 40%). RESULTS: Eleven RCTs involving 943 patients (121 males and 822 females; mean age 46.2 years; mean operative duration 84.4 min) were included. Overall, all outcomes were supported by moderate-certainty evidence, except for postoperative pain at 8 h, which was supported by low-certainty evidence. Postoperative pain scores were lower in the lidocaine group at time points (1, 4, 12, 24, and 48 h). At 24 h, pain outcomes favoured lidocaine (standardised mean difference [SMD] - 0.52, 95% CI - 1.01 to - 0.03; P = 0.0417; I² = 88.2%), and this benefit persisted at 48 h (SMD - 0.36, 95% CI - 0.68 to - 0.03; P = 0.0303; I² = 34.1%). Lidocaine significantly improved QoR on postoperative day 1 (MD 6.05, 95% CI 3.23 to 8.88; P < 0.0001; I² = 39.7%) and on day 2 (MD 6.52, 95% CI 4.97 to 8.06; P < 0.0001; I² = 0.0%). IV lidocaine significantly reduced the incidence of PONV compared with control (risk ratio [RR] 0.46, 95% CI 0.30 to 0.70; P = 0.0004; I² = 0.0%), while the requirement for rescue antiemetic therapy and the duration of anaesthesia did not differ significantly between groups. CONCLUSION: IV lidocaine was associated with reduced postoperative pain scores, nausea and vomiting, as well as improved QoR in patients undergoing thyroidectomy. However, the relationship between statistical significance and clinical relevance varied across pain outcomes. Accordingly, the clinical relevance of the analgesic effect should be interpreted with caution.