Analgesic efficacy of systemic lidocaine using lean body mass based dosing regime versus placebo in bariatric surgery: a prospective, randomised, double-blind, placebo-controlled, single-centre study

Intravenous lidocaine is used as an adjuvant analgesic agent in perioperative settings. It has been investigated in various patient populations and surgical interventions, but there are limited data on its efficacy, particularly for patients undergoing bariatric surgery. Obese patients are at high risk of postoperative respiratory complications and can be expected to benefit from anaesthetic techniques that minimise opioid administration. We studied administration of lidocaine hydrochloride 1% i.v. to general anaesthesia at a dose of 1.5 mg kg−1 (lean body mass×1.28) or placebo in patients undergoing bariatric surgery. Subjects randomly assigned to each group were surveyed for 48 h after surgery for experienced pain (primary outcome), and administered opioids, postoperative nausea and vomiting (PONV), resumption of bowel function, and length of hospital stay (secondary outcomes). We recruited and randomised 140 subjects to either the lidocaine or placebo group; 137 completed the study. Subjects with pain numeric rating scale (NRS) >3 within the first 4 h postoperatively were similar in both groups (proportion of any NRS >3 within first 4 h lidocaine group: 47/68 (69%) vs placebo group: 44/69 (63%), P=0.507; within first h P=0.177, within second h P=0.513, within third h P=0.145, within fourth h P=0.510). There was no difference in maximal pain score, opioid consumption, recovery of bowel function, incidence of PONV, or length of hospital stay. Lidocaine does not improve postoperative pain scores, analgesia, or any secondary outcomes in patients undergoing bariatric surgery. NCT03667001.