Two Bupivacaine Concentrations for Rectus Intercostal Fascial Plane Block After Laparoscopic Cholecystectomy

Pain after laparoscopic cholecystectomy remains a clinically relevant problem despite the minimally invasive nature of the procedure, and current recommendations favour multimodal, opioid-sparing analgesia including regional techniques. The rectus intercostal fascial plane block (RIFPB) is a recently described interfascial technique in which local anesthetic is injected into the plane between the rectus abdominis muscle and the 6th and 7th costal cartilages, targeting the anterior and lateral cutaneous branches of the T6-T9 thoracoabdominal nerves. In a previous randomized controlled trial conducted at the investigators\' institution, bilateral RIFPB after laparoscopic cholecystectomy significantly reduced the need for rescue analgesia (17.9% versus 55.3%) and pain scores during the first 12 postoperative hours. That trial, however, used 30 mL of 0.25% bupivacaine per side (60 mL, 150 mg in total), a dose approaching the recommended upper limit, and its limitations section highlighted the need to determine whether comparable analgesia can be achieved with lower doses. Because the efficacy of fascial plane blocks depends on the spread of local anesthetic, large volumes are preferred, which increases total dose and the risk of local anesthetic systemic toxicity (LAST); reducing concentration as volume increases has therefore been recommended. Equal-volume comparisons in transversus abdominis plane and erector spinae plane blocks suggest that lower local anesthetic concentrations provide comparable analgesia. No study has yet compared different concentrations for RIFPB. The aim of this trial is to compare, at a fixed volume of 30 mL per side (60 mL in total), bilateral RIFPB performed with 0.25% bupivacaine, bilateral RIFPB performed with 0.125% bupivacaine, and routine analgesic management with port-site infiltration (control), in adults undergoing elective laparoscopic cholecystectomy under general anesthesia. Ninety patients will be randomly allocated in a 1:1:1 ratio. The primary outcome is total rescue tramadol consumption during the first 24 postoperative hours. Secondary outcomes are numeric rating scale (NRS) pain scores at rest and on movement, the proportion of patients requiring rescue analgesia, time to first rescue analgesic, the incidence of nausea, vomiting and pruritus, block-related complications and signs of LAST, patient satisfaction, and length of hospital stay. The investigators hypothesize that RIFPB at either concentration will reduce postoperative analgesic consumption and pain scores compared with the control group, and that the lower concentration will provide comparable analgesia while halving the total bupivacaine dose (75 mg instead of 150 mg) and thereby reducing the risk of LAST.