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

This prospective observational study is designed to evaluate the effects of modified thoracoabdominal nerve block through perichondrial approach (M-TAPA) and external oblique intercostal (EOI) plane block on intraoperative analgesia and opioid consumption in patients undergoing elective laparoscopic cholecystectomy. Abdominal wall blocks are widely used to improve perioperative analgesia; however, their impact on intraoperative opioid requirements when guided by objective nociception monitoring remains unclear.

All patients will receive standardized general anesthesia. Intraoperative analgesia will be 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)" will be used to assess nociceptive responses. Remifentanil infusion will be titrated according to SCA values to maintain adequate analgesia. Dose adjustments will be performed at predefined intervals, and changes will be considered valid only if sustained for a minimum duration.

Patients will receive either M-TAPA or EOI block as part of routine clinical practice. The choice of block will not be influenced by the investigators, in accordance with the observational design of the study. Data will be collected prospectively during the intraoperative period and postoperative follow-up.

The primary outcome of the study is the time-weighted average intraoperative remifentanil infusion rate (µg/kg/min). Secondary outcomes include total intraoperative remifentanil consumption (µg/kg), intraoperative hemodynamic parameters (heart rate and mean arterial pressure), frequency of deviations in SCA values from the target range, postoperative pain scores assessed using a numeric rating scale (NRS), time to first analgesic requirement, and total rescue analgesic consumption.

Perioperative analgesia will be standardized. All patients will receive intravenous dexketoprofen toward the end of surgery as part of routine clinical practice. Rescue analgesia will be provided with intravenous dexketoprofen when clinically indicated. Additional outcomes include postoperative nausea and vomiting and perioperative complications.

This study aims to provide objective data on the opioid-sparing effects of different abdominal wall block techniques when intraoperative analgesia is guided by nociception monitoring. The findings may contribute to optimizing analgesic strategies and improving perioperative pain management in laparoscopic surgery.