External Oblique Intercostal Plane Block for Postoperative Analgesia After Major Upper Abdominal Surgery

Postoperative pain after major upper abdominal surgery is common and may delay recovery and increase opioid-related adverse effects. The External Oblique Intercostal Plane Block (EOIB) is a novel fascial plane block intended to improve analgesia for upper abdominal incisions.

This study is a prospective, single-center, randomized, assessor-blinded controlled trial in adults (18-85 years, ASA I-III) scheduled for elective major upper abdominal laparoscopic-assisted surgery (e.g., gastric, hepatic, gallbladder, pancreatic procedures) with expected operative time ≥2 hours and planned use of IV patient-controlled analgesia (PCA). Participants will be randomized 1:1 using a computer-generated, variable block-size sequence with allocation concealment via opaque sealed envelopes. The block-performing anesthesiologist will not collect outcomes; outcome assessors will be blinded to group assignment.

After induction of general anesthesia and before surgical incision, patients in the intervention group will receive ultrasound-guided bilateral EOIB at the 6th rib level using an in-plane technique; 25 mL 0.3% ropivacaine per side. Control participants will receive no regional block. All participants will receive standardized multimodal analgesia including IV PCA, antiemetic prophylaxis (dexamethasone 5 mg; ondansetron as needed), and NSAID use per ERAS practice.

The primary endpoint is total opioid consumption during the first 24 hours after surgery, expressed as IV morphine milligram equivalents (MME), including PCA and rescue opioids. Secondary outcomes include postoperative pain scores (0-10 verbal rating scale) at prespecified time points (including 24, 48, and 72 hours; at rest and with activity as applicable), quality of recovery (QoR-15 at 24/48/72 hours), opioid consumption at 24-48 hours, postoperative nausea and vomiting within 72 hours, intraoperative hemodynamic events, time to first flatus, and postoperative length of stay.

Inclusion criteria

• Obtain written informed consent from participants or their legal representatives
• Age between 18 and 85 years
• American Society of Anesthesiologists (ASA) physical status classification I-III
• Scheduled for elective laparoscopic major upper abdominal surgery (e.g., gastric, hepatic, gallbladder, pancreatic surgery)
• Expected surgical duration ≥ 2 hours
• Ability to use the intravenous patient-controlled analgesia (IV PCA) system

Exclusion criteria

• Hepatic disease (liver enzyme levels ≥ 2× the upper limit of normal)
• Renal disease (serum creatinine levels ≥ 2× the upper limit of normal)
• Allergy to local anesthetics or known study-related drugs
• Pregnancy or lactation
• Low surgical incision site (not involving the upper abdominal wall innervated by T6-T10 nerves)
• Coagulopathy or current use of anticoagulant medications
• Opioid use for more than 2 weeks in the past 6 months