External Oblique Intercostal Block vs Erector Spinae Plane Block for Postoperative Analgesia After Laparoscopic Cholecystectomy

This study is designed as a multicenter, prospective, randomized controlled trial aiming to evaluate and compare the postoperative analgesic outcomes of two ultrasound-guided regional anesthesia techniques, external oblique intercostal block (EOIB) and erector spinae plane block (ESPB), in adult patients undergoing elective laparoscopic cholecystectomy.EOIB and ESPB are ultrasound-guided regional anesthesia techniques that have been described for postoperative analgesia in upper abdominal surgery. In this study, the regional analgesic technique to be administered will be determined by randomization, while all other aspects of perioperative care will follow standard institutional practice. Except for the randomized allocation of the regional block technique, the research team will not alter routine anesthetic management.

The primary objective of the study is to compare cumulative intravenous morphine consumption during the first 24 hours after surgery between patients receiving EOIB and those receiving ESPB. Secondary objectives include assessment of postoperative pain scores at rest and during movement, quality of recovery, postoperative nausea and vomiting (PONV), intraoperative opioid consumption, rescue analgesic requirements, block-related complications, and opioid-related adverse effects.

Clinical Routine and Analgesic Protocol

All patients will be managed according to the standard multimodal analgesia protocol routinely used in the general surgery operating rooms of the participating institutions. Preoperatively, standard ASA monitoring will be applied, intravenous access will be established, and perioperative fluid management will be provided according to institutional practice. Mild sedation will be administered using intravenous midazolam at a dose of 0.02 mg/kg. Supplemental oxygen will be delivered via nasal cannula during block performance.

General anesthesia will be induced and maintained using routinely applied anesthetic agents. Intraoperative opioid administration will be titrated according to hemodynamic parameters to maintain mean arterial pressure and heart rate within acceptable limits, and total intraoperative opioid consumption will be recorded.

Postoperatively, all patients will receive intravenous paracetamol and intravenous tramadol as part of routine analgesic care. Intravenous morphine patient-controlled analgesia (PCA) will be provided to all patients using standardized settings, including a 1 mg bolus dose, a 10-minute lockout interval, and a 4-hour limit of 20 mg. Rescue analgesia will consist of intravenous tramadol infusion when pain remains uncontrolled (NRS ≥4), followed by intravenous morphine if necessary, according to the predefined protocol.

Block Techniques (Performed as Part of Study Protocol)

EOIB Group:

Patients allocated to the EOIB group will receive bilateral ultrasound-guided external oblique intercostal block approximately 45 minutes before surgery. With the patient in the supine position, a high-frequency linear ultrasound probe will be placed longitudinally along the anterior midaxillary line. Using an in-plane approach, a block needle will be advanced into the fascial plane deep to the external oblique muscle. A total volume of 30 mL of 0.25% bupivacaine will be administered bilaterally. The block will be performed by experienced anesthesiologists.

ESPB Group:

Patients allocated to the ESPB group will receive bilateral ultrasound-guided erector spinae plane block approximately 45 minutes before surgery. With the patient in the sitting position, following skin disinfection and sterile preparation, a convex ultrasound probe will be placed in a sagittal orientation approximately 2-3 cm lateral to the T7 spinous process. Using an in-plane approach, the needle will be advanced into the fascial plane deep to the erector spinae muscle. A total volume of 30 mL of 0.25% bupivacaine will be administered bilaterally, with sonographic confirmation of cranial and caudal spread.

Postoperative Assessment

Postoperative pain will be assessed using the 11-point Numeric Rating Scale (NRS; 0-10) at rest and during movement (deep breathing or coughing) at 0, 3, 6, 12, 18, and 24 hours after surgery. PONV will be evaluated using a verbal descriptive scale, and antiemetic treatment will be administered as needed according to institutional protocols.

Quality of recovery and patient satisfaction will be assessed using the Turkish version of the Quality of Recovery-15 (QoR-15) questionnaire at 24 hours postoperatively. Intraoperative opioid consumption, time to first PCA demand, rescue analgesic requirements, block-related complications (including pneumothorax, hematoma, vascular puncture, epidural spread, intrathecal injection, and local anesthetic systemic toxicity), and opioid-related side effects such as nausea, sedation, and respiratory depression will be recorded.

Dermatomal sensory block distribution will be assessed using a pinprick test with a 27-gauge needle 30 minutes after block application.

All data will be collected by trained personnel blinded to group allocation. Due to the low-risk nature of the interventions and the short follow-up period, no independent data monitoring committee has been established.