Ultrasound-Guided Transversus Abdominis Plane Block Using 0.125% versus 0.25% Bupivacaine for Postoperative Opioid Consumption in Kidney Transplant Recipients: A Prospective, Randomized, Double-Blind Clinical Trial.

Purpose: Transversus abdominis plane (TAP) block is a widely accepted technique for postoperative pain management in kidney transplant (KT) patients, typically with 0.25-0.5% bupivacaine. Lower concentrations, such as 0.125%, may reduce systemic toxicity while remaining effective. This study aimed to compare the efficacy and safety of 0.125% versus 0.25% bupivacaine for TAP block in KT patients. Patients and Methods: In this prospective, double-blind, randomized trial, KT patients received either 0.125% or 0.25% bupivacaine for ultrasound-guided TAP block prior to surgery, followed by intravenous fentanyl patient-controlled analgesia postoperatively. The primary outcome was 24-hour fentanyl consumption. Secondary outcomes included intraoperative fentanyl use, time to first analgesic request, pain scores, TAP block complications, opioid-related side effects, and patient satisfaction. Results: Seventy-six patients were enrolled, with 74 completing the study (37 per group). Baseline characteristics were comparable between groups. Intraoperative fentanyl use was significantly lower in the 0.25% bupivacaine group (140.5 ± 39.7 mcg) compared to the 0.125% group (166.8 ± 44.7 mcg; Conclusion: TAP block with 0.125% bupivacaine provided comparable postoperative opioid consumption and pain scores to 0.25%, without associated complications.