The effect of intravenous lidocaine infusion on subarachnoid anesthesia in patients undergoing total knee replacement: a randomised controlled trial

Purpose Intravenous lidocaine is a non-opioid analgesic adjunct for perioperative pain relief. The aim of our study was to explore whether concurrent administration of intravenous lidocaine prolongs the duration of sensory block during total knee replacement (TKR) under spinal anaesthesia. Methods This prospective randomized double blind controlled trial was conducted on 28 patients (14 in lidocaine group and 14 in the control group) undergoing unilateral TKR under spinal anesthesia. In the lidocaine group, intravenous lidocaine 1.5 mg<middle dot>kg(-1) followed by an infusion of 1.5 mg<middle dot>kg(-1)<middle dot>h(-1) was administered intraoperatively after spinal anesthesia. The primary outcome was the duration of sensory block of spinal anesthesia. Secondary outcomes included onset time of sensory and motor block, duration of motor block, time to first postoperative analgesic, postoperative visual analog scale (VAS) scores and postoperative analgesia requirement in 24 h after surgery. Results The duration of sensory and motor block was longer in the lidocaine group (Mean +/- SD; 112.50 +/- 5.80 min versus 78.21 +/- 9.12 min; p < 0.001 and 237.14 +/- 9.14 min versus 215.00 +/- 10.12 min; p < 0.001, respectively). Time to requirement of first rescue analgesia was 184.29 +/- 9.38 min in the lidocaine group and 127.14 +/- 23.35 min in the control group (p < 0.001). VAS scores were lower in the lidocaine group at 4, 8, 12 and 24 h after surgery (p < 0.00001, p < 0.00001, p < 0.00006, p = 0.032, respectively). Requirement of additional analgesia in the first 24 h was higher in the control group. There were no clinical signs to suggest lidocaine toxicity in any patient. Conclusion During unilateral TKR under spinal anaesthesia, concurrent use of intravenous lidocaine prolonged sensory block and reduced postoperative analgesic requirements.