Unilateral subcostal anterior quadratus lumborum block versus intrathecal morphine for postoperative pain in laparoscopic nephrectomy: a randomized controlled trial

Intrathecal morphine (ITM) offers effective analgesia after laparoscopic nephrectomy but may cause side effects. The anterior subcostal quadratus lumborum (QL) block has been proposed as a safer alternative. This study evaluated whether anterior subcostal QL block is non-inferior to ITM in reducing postoperative opioid use. This single-center, randomized, observer-blinded, non-inferiority trial allocated 80 adult patients undergoing elective laparoscopic nephrectomy to receive single-injection unilateral anterior subcostal QL block (0.25% bupivacaine (0.4 mL/kg) containing epinephrine 1:400,000) or spinal anesthesia with 5 mcg/kg ITM (maximum 200 mcg) plus 7.5 mg isobaric bupivacaine. The primary outcome was the 24-hour cumulative intravenous morphine milligram equivalent (MME). Pain scores were recorded at rest and during activity at 0, 3, 6, 12, and 24 hours postoperatively. Patient satisfaction, recovery quality, and adverse effects were also evaluated. The median difference in 24 hours intravenous MME consumption between anterior subcostal QL block and ITM was 9.5 mg (95% CI 7 to 12; p<0.001), exceeding the non-inferiority margin. Patients with ITM reported lower pain scores and greater satisfaction at 24 hours (median (Q1-Q3), ITM 108 (102.25-113.5) vs anterior subcostal QL block 75.5 (58-100)) and discharge (ITM 117 (115-123.75) vs anterior subcostal QL block 94 (77-110); p<0.001). However, no between-group differences were observed in 30-day complication rates, including the Clavien-Dindo and Comprehensive Complication Index scores. Adverse effects, such as nausea, pruritus, and respiratory events, were comparable. Although designed as a non-inferiority trial, anterior subcostal QL block did not meet the threshold. While ITM resulted in lower opioid use, the study was not powered to establish superiority. Anterior subcostal QL block may be considered for patients at risk of ITM-related respiratory depression; however, its inconsistent cranial spread and limited visceral analgesia may explain its lower efficacy. Caution is also required in anticoagulated patients because of the deep anatomical location of the block. ClinicalTrials.gov: NCT06630858.