Perioperative intravenous lidocaine infusion for postoperative pain control: a meta-analysis of randomized controlled trials

Various strategies have been proposed for postoperative pain control. Among those, intravenous lidocaine infusion (IVLI) has gained in interest. However, its clinical benefit remains unclear. This systematic review is an evaluation of the analgesic efficacy and safety of IVLI during general anesthesia.A systematic search was performed using MEDLINE, EMBASE, Cochrane, and SCOPUS databases, likewise, grey literature. The review included all randomized controlled trials that used a placebo or any comparator and evaluated IVLI during general anesthesia for any type of surgery. Primary outcomes were pain control and opioid requirement. Secondary outcomes were mortality, length of stay, ileus recovery time, nausea/vomiting, and adverse events. Random effects models were used and heterogeneity was assessed using the I2 index.From 5,472 citations retrieved, 29 studies involving a total of 1,754 patients met eligibility. At six hours postoperatively, intravenous lidocaine infusion reduced pain at rest (weighted mean difference [WMD]-8.70, 95% confidence intervals [CI] -16.19 to -1.21), during cough (WMD -11.19, 95% CI -17.73 to -4.65), and during movement (WMD -9.56, 95% CI -17.31 to-1.80). Intravenous lidocaine infusion also reduced opioid requirement (morphine) (WMD -8.44 mg, 95% CI -11.32 to -5.56), time to first flatus (WMD -7.62 hr, 95% CI-10.78 to -4.45), time to first feces (WMD -10.71 hr, 95% CI -16.14 to -5.28), nausea/vomiting (risk ratios = 0.71, 95% CI 0.57-0.90), and hospital length of stay (WMD -0.17 days, 95% CI -0.41 to 0.07). Abdominal surgery was strongly associated with benefit. For the 12 studies that systematically screened adverse events, the incidence of cardiac and neurologic adverse events was comparable. Eight studies observed toxic plasma levels.Perioperative IVLI reduced postoperative pain and opioid requirement, as well as ileus recovery time, hospital length of stay, and nausea/vomiting. Intravenous lidocaine infusion was effective mainly in abdominal surgery populations. Considering that toxic levels were detected and that adverse events were not systematically screened for in most studies, dose and safety of IVLI should be established before recommending its use.