This randomized controlled trial aims to compare the analgesic efficacy of bilateral ultrasound-guided erector spinae plane block (ESPB) versus bilateral external oblique intercostal plane (EOI) block in patients undergoing open cholecystectomy.

Patients will be randomly allocated into two groups to receive either ESPB or EOI block in addition to standard general anesthesia. The primary outcome is postoperative pain score assessed using the Numerical Rating Scale (NRS) at 2 hours after surgery. Secondary outcomes include intraoperative opioid consumption, postoperative nalbuphine requirements, time to first analgesic request, and hemodynamic changes.

This study seeks to determine the more effective regional anesthesia technique for improving perioperative analgesia in open cholecystectomy.

Open cholecystectomy is still indicated in selected patients such as those with complicated gallbladder disease or contraindications to laparoscopy. Effective perioperative pain management is essential to improve patient outcomes and reduce opioid consumption.

Regional anesthesia techniques have gained increasing interest, particularly with the use of ultrasound guidance. The erector spinae plane block (ESPB) is a relatively simple and widely used interfascial block that provides effective analgesia for abdominal surgeries. The external oblique intercostal plane (EOI) block is a newer technique targeting the upper abdominal wall.

In this prospective, randomized, double-blinded clinical trial, adult patients undergoing elective open cholecystectomy will be randomized into two groups. One group will receive bilateral ultrasound-guided ESPB, while the other group will receive bilateral ultrasound-guided EOI block, both performed after induction of general anesthesia and before surgical incision.

All patients will receive standardized general anesthesia. Pain will be assessed using the Numerical Rating Scale (NRS) at multiple time points postoperatively. Rescue analgesia with intravenous nalbuphine will be administered as needed.

The primary outcome is postoperative pain score at 2 hours. Secondary outcomes include intraoperative fentanyl consumption, total nalbuphine consumption over 24 hours, time to first analgesic request, hemodynamic parameters, and any block-related complications.

This study aims to provide evidence regarding the comparative effectiveness of ESPB and EOI block in open cholecystectomy surgeries.

Inclusion Criteria:

• Adult patients aged 18-65 years.
• Patients scheduled for elective open cholecystectomy.
• American Society of Anesthesiologists (ASA) physical status I-II.
• Patients who provide informed consent.

Exclusion Criteria:

• Patient refusal.
• Known allergy to local anesthetics.
• Coagulopathy or anticoagulant therapy.
• Infection at the site of injection.
• Severe hepatic, renal, or cardiac disease.
• Body mass index (BMI) > 35 kg/m².
• Pregnancy.

Individual participant data (IPD) will not be shared. The study investigators do not plan to make individual-level data publicly available. Results will be reported in aggregate form to ensure participant confidentiality.

The study is double-blinded. The anesthesiologist performing the block is not involved in intraoperative management or postoperative assessment. Patients, intraoperative care providers, and outcome assessors are blinded to group allocation.