Analgesic Effect of Ultrasound-Guided Caudal Block Versus Quadratus Lumborum Plane Block in Lumbar Spine Surgery in Adult Patients: A Double-Blinded Prospective Comparative Study.

Background: Postoperative pain following lumbar spine surgery (LSS) can significantly impact recovery and patient satisfaction. Ultrasound-guided regional techniques such as quadratus lumborum plane block (QLPB) and caudal block (UGCB) have been proposed to enhance postoperative analgesia while reducing opioid consumption and opioid-related adverse effects (AEs). Objectives: To compare the analgesic efficacy and safety of ultrasound-guided QLPB versus ultrasound-guided caudal block in adult lumbar spine stabilization surgery. Methods: This randomized, double-blinded, prospective comparative study included 111 adult patients (18 - 60 years, ASA physical status I - II) scheduled for elective lumbar spine stabilization surgery. Patients were randomly allocated into three equal groups: Control (standard analgesia), ultrasound-guided caudal block (UGCB), or ultrasound-guided QLPB. Blocks were performed under ultrasound guidance after induction of general anesthesia using 0.25% bupivacaine. The primary outcome was the time to first postoperative rescue analgesia. Secondary outcomes included postoperative pain scores using the Numerical Pain Rating Scale (NPRS), total 24-hour postoperative opioid (meperidine) consumption, intraoperative opioid requirements, hemodynamic variables, and block- or opioid-related adverse events over the first 24 postoperative hours. Results: The time until the initial rescue analgesia was significantly delayed with QLPB in comparison to control and Caudal, with medians of 15, 1, and 5 h, respectively (P < 0.001). The total 24-hour (meperidine) intake was significantly diminished with QLPB as opposed to Caudal and control (P < 0.05). Numerical Pain Rating Scale scores were significantly diminished in QLPB and Caudal as opposed to control at 30 min, 1, 2, 4, 8, and 24 h (P < 0.001), with comparability detected at 12 h and 18 h. Intraoperative fentanyl administration was markedly diminished in the QLPB and Caudal groups, in contrast to the control group (P < 0.001). The occurrence of nausea and vomiting exhibited comparability across groups. Conclusions: Both ultrasound-guided caudal block and QLPB significantly improved postoperative analgesia compared with standard analgesic management following lumbar spine stabilization surgery. However, QLPB provided longer-lasting analgesia and was associated with lower postoperative opioid consumption than caudal block, highlighting its advantage for prolonged postoperative pain control.