Early postoperative pain and opioid use after liver surgery: A systematic review and meta-analysis

Background Postoperative pain following liver resection remains a clinical challenge, and the optimal analgesic strategy is still debated. Objective To determine whether a single intrathecal morphine injection provides superior analgesia and opioid-sparing effects compared with conventional systemic or regional techniques in adult patients undergoing liver surgery. Methods PubMed, Embase, Web of Science citation index, and the Cochrane Library were searched from inception to August 2025 for randomized controlled trials comparing intrathecal morphine with alternative analgesic regimens in liver resection. The primary outcome was pain intensity at rest 24 h after surgery (standardized mean difference). Secondary outcomes included pain intensity at 48 and 72 h and cumulative opioid consumption within 24 h postoperatively. Random-effects meta-analyses and I² statistics were used to assess pooled effects and heterogeneity. Results Eleven randomized controlled trials (n = 535) met the inclusion criteria. Intrathecal morphine reduced 24-h postoperative pain scores with a moderate effect (standardized mean difference = −0.64; 95% confidence interval: −0.84 to −0.44; p < 0.001; I 2 = 55%) and decreased 24-h opioid consumption by 11.6 mg morphine equivalents (95% confidence interval: −19.3 to −3.9 mg; p = 0.003; I 2 = 96%). Differences in pain intensity at 48 and 72 h were not statistically significant. Adverse-event profiles were comparable between groups. Conclusion A single dose of intrathecal morphine provides clinically meaningful early analgesia and opioid-sparing benefits after liver resection without increasing adverse events. Incorporating intrathecal morphine into multimodal analgesic protocols may accelerate recovery; however, further high-quality trials are warranted to refine dosing and identify optimal patient selection.