Abstract
Background Perioperative lidocaine infusion benefits abdominal surgery patients, but the optimal dose in elderly patients remains unclear. While Transversus Abdominis Plane (TAP) block is a recognized analgesic method, its combination with lidocaine infusion in elderly patients needs further investigation. This study aims to assess the impact and safety of different lidocaine infusion doses combined with ropivacaine TAP block on postoperative analgesia in elderly patients undergoing colorectal cancer resection.Methods Patients (n = 55 per group) were randomized into four groups. After a preoperative 0.25% ropivacaine bilateral TAP block, patients received perioperative 1% lidocaine at 0.5, 1.0, or 1.5 mg/kg/h, or normal saline (placebo). Postoperatively, lidocaine groups used PCIA devices delivering lidocaine at 0.3–1.5 mg/kg/h for 72 hours; the placebo group received saline. The primary outcome was the incidence of moderate-to-severe pain during activity 24 hours postoperatively. Secondary outcomes included pain during movement and at rest over three days, quality of recovery, bowel function recovery time, postoperative morphine use, and adverse events related to opioids and local anesthetics. Plasma lidocaine levels were measured post-surgery and at 24 hours.Results The lidocaine 1.5 group had a significantly lower incidence of moderate-to-severe postoperative pain during movement compared to the control group at 24 hours (38.2% vs. 65.5%, Bonferroni corrected P = 0.004). No significant differences were observed in the lidocaine 1.0 or 0.5 groups. Other outcomes, including postoperative quality of recovery, morphine consumption, bowel function recovery time, and adverse reactions to opioids, were similar across groups (all P > 0.05). Only one instance of plasma lidocaine concentration exceeding 4.0 µg/ml was observed, with no serious adverse events.Conclusions For elderly patients, a 1.5 mg/kg/h lidocaine infusion may be safer and more effective, serving as a cornerstone for future research.Trial registration: Registered 25 May 2022—Retrospectively registered, https://classic.clinicaltrials.gov/ct2/results?term=NCT05412576