The effect of lidocaine patch for postoperative pain: A meta-analysis of randomized controlled trials

Study objective: The role of lidocaine patch (LP) in reducing postoperative pain by local anesthetic absorption has been evaluated in several studies; however, these trials have shown inconsistent results. This meta-analysis aimed to identify the benefits of LP, focusing on its pain-reducing and morphine-sparing effect in patients after surgery. Design: Meta-analysis. Setting: Published randomized controlled trials (RCTs) comparing the analgesic effects of LP after surgery to those of placebo or no patch. Patients: Eleven RCTs including 539 patients. Interventions: We searched electronic databases to identify relevant RCTs. Measurements: The primary outcome was postoperative pain score up to 48 h assessed using a numerical rating or visual analog scale, and the secondary outcomes were postoperative morphine consumption and side effects. The effect size was estimated by calculating the mean difference (MD) or risk ratio (RR), with 95% confidence interval (CI). Main results: LP significantly decreased postoperative pain score at 6 h (MD, −1.85; 95% CI, −2.98 to −0.72; p = 0.001), 12 h (MD, −1.48; 95% CI, −2.07 to −0.88; p < 0.001), 24 h (MD, −1.18; 95% CI, −1.65 to −0.7; p < 0.001), and 48 h (MD, −1.33; 95% CI, −2.46 to −0.19; p = 0.022). In contrast, no significant effect on postoperative morphine consumption was observed at 24 h (MD, −3.48 mg; 95% CI, −7.94 to 0.98 mg; p = 0.127) or 48 h (MD, −5.29 mg; 95% CI, −13.28 to 2.71; p = 0.195). LP was unrelated to local (RR, 1.00, 95% CI, 0.67 to 1.49; p = 0.987) or systemic side effects (RR, 0.76, 95% CI, 0.52 to 1.11, p = 0.151). Conclusions: LP can lower postoperative pain without side effects, compared to placebo or no patch. However, its morphine-sparing effect remains unclear.