Twenty-eight patients undergoing unilateral total knee replacement under spinal anesthesia were randomized to receive either intravenous lidocaine infusion (n=14) or normal saline (n=14). The primary outcome was the duration of sensory block after spinal anesthesia. Secondary outcomes included onset time of sensory and motor block, duration of motor block, time to first postoperative analgesic request, postoperative pain scores (VAS), and the requirement for additional analgesia in the first 24 hours. Outcomes were assessed during surgery and up to 24 hours postoperatively. Overall, the study showed that intravenous lidocaine significantly prolonged the sensory block and motor block duration, delayed the first postoperative analgesic request, and reduced postoperative pain scores and additional analgesia needs. These findings suggest that intravenous lidocaine infusion is a useful perioperative analgesic adjunct in total knee replacement.