Comparison of M-TAPA and External Oblique Intercostal Block for Intraoperative Opioid Consumption in Laparoscopic Cholecystectomy

This prospective, randomized, interventional study compares the effects of modified thoracoabdominal nerve block through perichondrial approach (M-TAPA) and external oblique intercostal plane block (EOI) on intraoperative analgesia and opioid consumption in patients undergoing elective laparoscopic cholecystectomy. Eighty patients are randomized into two groups: the M-TAPA group and the EOI group. All patients receive standardized general anesthesia. Intraoperative analgesia is guided using the Skin Conductance Algesimeter (SCA), which reflects sympathetic nervous system activity by measuring fluctuations in skin conductance. The SCA parameter "peaks per second (PPS)" is used to assess nociceptive responses, and remifentanil infusion is titrated according to SCA values. Patients assigned to the M-TAPA group receive bilateral ultrasound-guided M-TAPA block, while patients assigned to the EOI group receive bilateral ultrasound-guided external oblique intercostal plane block. In both groups, 20 mL of 0.25% bupivacaine is administered on each side. Perioperative analgesia is standardized. All patients receive intravenous dexketoprofen toward the end of surgery. During postoperative follow-up, intravenous paracetamol is administered as rescue analgesia when the numeric rating scale (NRS) pain score is 4 or higher. The primary outcome is the time-weighted average intraoperative remifentanil infusion rate (µg/kg/min). Secondary outcomes include total intraoperative remifentanil consumption, intraoperative hemodynamic parameters, SCA measurements, postoperative pain scores, time to first rescue analgesic requirement, rescue analgesic consumption, postoperative nausea and vomiting, and perioperative complications. The study aims to compare the opioid-sparing and analgesic effects of M-TAPA and EOI under objective nociception-guided intraoperative analgesia.

Inclusion Criteria: * Patients aged 18-80 years * ASA physical status I-III * Scheduled for elective laparoscopic cholecystectomy under general anesthesia * Ability to provide written informed consent Exclusion Criteria: * Patient refusal * Known allergy to local anesthetics * Chronic opioid use or opioid dependence * Neurological or psychiatric disorders affecting pain perception * Use of medications affecting autonomic nervous system activity, such as beta-blockers * Infection at the injection site * Coagulopathy or anticoagulant therapy * Pregnancy