Sensory Analysis and Cutaneous Mapping of Different Regional Anesthesia Techniques

Overview

This prospective observational study aims to evaluate and compare the sensory block distribution and regression patterns of two regional anesthesia techniques - External Oblique Plane Block (EOPB) and Serratus Intercostal Plane Block (SIPB) - in patients undergoing laparoscopic cholecystectomy. Thirty adult patients (ASA I-III, BMI ≤ 35 kg/m², ≥50 kg) scheduled for elective laparoscopic cholecystectomy procedures will be included, with 20 in each block group. Sensory block areas will be assessed using pinprick test, and dermatomal mapping will visualize the spread. The findings are expected to improve understanding of block behavior and guide multimodal analgesia strategies in laparoscopic cholecystectomy.

This single-center, prospective observational study will be conducted at Samsun University Training and Research Hospital operating rooms between November 2025 and June 2026. The study will include patients aged 18-75 years, classified as ASA I-III, who are scheduled for elective laparoscopic cholecystectomy and have provided written informed consent. For pain management, these patients will undergo either serratus intercostal plane block (SIPB) or external oblique plane block (EOPB) under ultrasound guidance. Patients receiving one of these two block techniques will be observed, and the sensory block areas created will be evaluated. Both blocks will be performed bilaterally and under ultrasound guidance immediately before surgery. 0.25% bupivacaine will be used for the block applications, and 25 mL of local anesthetic will be injected into each side (a total of 50 mL). Thirty minutes after the block, patients will be evaluated for cutaneous sensory block using the "pinprick test." This evaluation will be standardized according to specific dermatome levels, covering the midline and both abdominal quadrants, in order to describe sensory loss on the skin. The data obtained will be analyzed to determine the dermatomal spread and the minimum and maximum areas of effect of the blocks. Additionally, findings related to block application time will be recorded observationally. A comparison between the groups will be made, and the degree of overlap between the sensory block areas and the surgical incision site will be evaluated.