This randomized controlled clinical trial investigates the comparative efficacy of two novel regional anesthesia techniques - the Erector Spinae Plane Block (ESPB) and the External Oblique Intercostal Plane Block (EOPB) - for postoperative analgesia in patients undergoing elective laparoscopic cholecystectomy under general anesthesia.

A total of 90 patients aged 18-65 years, with ASA physical status I or II, were randomly assigned to one of three groups: ESPB, EOPB, or control. Blocks were performed under ultrasound guidance prior to surgical incision. Pain intensity was evaluated using the Visual Analog Scale (VAS), and rescue analgesic consumption was recorded over the first 24 hours postoperatively.

The study aims to determine whether ESPB or EOPB offers superior pain control and reduced opioid consumption, and to assess patient satisfaction and safety. The results will inform multimodal analgesia strategies for upper abdominal laparoscopic surgery.

Laparoscopic cholecystectomy (LC) is one of the most commonly performed upper abdominal surgeries. Despite being minimally invasive, LC is frequently associated with significant postoperative pain originating from both visceral and somatic sources. Inadequate pain control may lead to delayed recovery, increased opioid consumption, and patient dissatisfaction.

Regional anesthesia techniques have become increasingly important components of multimodal analgesia protocols for abdominal surgeries. Two recently described fascial plane blocks - the Erector Spinae Plane Block (ESPB) and the External Oblique Intercostal Plane Block (EOPB) - have shown promising results in reducing postoperative pain in thoracic and abdominal procedures.

This prospective, randomized, controlled clinical trial was conducted to evaluate and compare the analgesic effectiveness of ESPB and EOPB in patients undergoing elective LC under general anesthesia. After obtaining ethical approval (Protocol No: 2024/17/840-938) and informed consent, 90 adult patients aged 18-65 years with ASA physical status I or II were enrolled.

Participants were randomized into three groups using a sealed envelope technique:

Group 1 (ESPB): Received bilateral ultrasound-guided ESPB at the T7-8 level using 20 mL of local anesthetic solution (10 mL 0.5% bupivacaine + 10 mL 2% lidocaine) preoperatively.

Group 2 (EOPB): Received ultrasound-guided EOPB using the same volume and mixture of local anesthetic.

Group 3 (Control): Did not receive any regional block.

Postoperative pain was assessed using the Visual Analog Scale (VAS) at regular intervals (15 minutes, and at 2, 4, 8, 12, 16, and 24 hours). Rescue analgesia consisted of 50 mg dexketoprofen trometamol administered when VAS ≥4. If pain persisted, 50 mg tramadol was given as a second-line analgesic.

Primary endpoints included postoperative VAS scores and total rescue analgesic consumption over 24 hours. Secondary endpoints included time to first analgesic requirement, side effects, complications related to blocks, and patient satisfaction.

Initial results indicated that both ESPB and EOPB significantly reduced postoperative pain and analgesic requirements compared to the control group. While EOPB was technically easier to perform, ESPB provided longer-lasting analgesia. These findings may support the integration of ESPB or EOPB into routine multimodal analgesia protocols for laparoscopic abdominal surgeries.

Inclusion Criteria:

• Age 18-65 years
• ASA physical status I-II
• Undergoing elective laparoscopic cholecystectomy under general anesthesia
• Provided informed written consent
• BMI between 18.5 and 30 kg/m²
• Able to follow study instructions

Exclusion Criteria:

• Allergy to local anesthetics
• Chronic opioid use or chronic pain
• Coagulopathy or anticoagulant use
• Severe organ dysfunction
• Pregnancy or breastfeeding
• Neurological or psychiatric disorders
• Infection at injection site
• Refusal to participate

Individual participant data (IPD) will not be shared. The study was conducted as part of a postgraduate academic thesis, and ethical approval limits data use to the original analysis only. No public data repository or external sharing is planned.

The local anesthetic to be used in the study was prepared by two researchers who were not involved in the anesthesia application and did not participate in the postoperative data collection process. Postoperative patient data were recorded with the random ID assigned to each patient, and the researchers who collected data during this process were not informed about the patient groups. In addition, the anesthesiologist who performed the simple randomization also performed the nerve block, but was not involved in the collection of postoperative data. The anesthesiologists responsible for the anesthesia management and data collection process were not informed about the group distribution, and thus the study was conducted in a double-blind manner.