External oblique intercostal plane block improves early postoperative analgesia after open liver surgery: A randomized, double-blind, controlled trial

Background The external oblique intercostal (EOI) plane block is a fascial plane block that targets the unilateral cutaneous branches of intercostal nerves, and spares the sympathetic trunk. We hypothesized that the ultrasound-guided EOI plane block might provide superior analgesia compared to systemic analgesia alone for patients after open liver surgery. Methods In this double-blind, randomized controlled trial, 74 patients scheduled for open liver surgery were assigned to receive either EOI plane block with 30 mL of 0.375% ropivacaine ( n = 37) or no EOI plane block ( n = 37). All patients received postoperative standard patient-controlled intravenous analgesia. Primary outcome was the resting numerical rating scale (NRS) pain score at 3 h postoperatively. The key secondary outcomes included opioid consumption, and the total number of analgesia interventions at 3 h, 6 h, 24 h, 48 h, and 72 h postoperatively; opioid-related side effects and block-related complications; postoperative functional recovery outcomes; total ropivacaine plasma concentrations at 5, 10, 30, 60, 120, and 180 min post-block. Results The primary outcome, the resting NRS pain score at 3 h postoperatively, was significantly lower in the block group than in the control group. The block group showed a shorter length of hospital stay. There were no significant differences in cumulative opioid consumption, frequency of analgesia, or opioid-related side effects. No block-related complications were observed, and total ropivacaine plasma concentrations remained below the toxicity threshold. Conclusions Ultrasound-guided EOI plane block reduces early postoperative pain. This technique should be regarded as a safe and effective component within a comprehensive postoperative multimodal analgesia regimen.