The effect of continuous intravenous lidocaine infusion on postoperative analgesia in elderly patients undergoing laparoscopic colorectal surgery.

BACKGROUND: This study aimed to evaluate the effect of continuous intravenous infusion of different doses of lidocaine on postoperative analgesia in elderly patients undergoing laparoscopic colorectal surgery. METHODS: In this prospective, randomized, double-blind pilot study, elderly patients undergoing laparoscopic colorectal surgery at the Affiliated Cancer Hospital of Guizhou Medical University between January 2024 and February 2025 were enrolled. All patients received anterior quadratus lumborum block under ultrasound guidance combined with general anesthesia. Participants were randomized into three groups based on the lidocaine infusion dose after tracheal intubation: Group L (1.0 mg/kg/h), Group M (1.5 mg/kg/h), and Group H (2.0 mg/kg/h). The primary outcome was postoperative pain intensity assessed by the Numeric Rating Scale (NRS) at predefined time points. Secondary outcomes included patient-controlled analgesia (PCA) usage, postoperative opioid consumption, requirement of intraoperative ephedrine, Modified Observer’s Assessment of Alertness/Sedation (MOAA/S) scores, and incidence of postoperative adverse events. RESULTS: A total of 114 patients aged ≥ 65 years (52 males and 62 females) were included with 38 cases in each group. Baseline demographic and clinical characteristics were comparable among the three groups. There were significant differences in postoperative pain NRS scores at 12-hour and 24-hour among three groups (both P < 0.001). Compared with the L group, the postoperative 12-hour and 24-hour pain NRS scores were significantly lower in both the M and H groups (P < 0.05) Compared to Group L, both Group M and Group H demonstrated significantly reduced cumulative PCA usage and postoperative opioid consumption (P < 0.05). Group H showed a higher requirement for intraoperative ephedrine compared to Groups L and M (P < 0.05). Upon entry into the post-anesthesia care unit, Groups L and M had significantly higher MOAA/S scores than Group H (P < 0.05). No significant differences were found in the incidence of adverse events among three groups (P > 0.05). CONCLUSION: In elderly patients undergoing laparoscopic colorectal surgery, continuous intravenous lidocaine infusion at 2.0 mg/kg/h significantly reduced postoperative pain intensity at 12 and 24 h compared with 1.0 mg/kg/h. Based on these findings, the effective dosage range appears to be 1.5–2.0 mg/kg/h. Further studies with larger sample sizes are needed to confirm these results. CLINICAL TRIAL NUMBER: ChiCTR2500097315 (Retrospectively registered).