Efficacy of the Quadratus Lumborum Block for Postoperative Pain Control in Patients Undergoing Elective Open Colorectal Surgery: A Randomized Double-blinded Controlled Trial

<title>Abstract</title> <p> <bold>Background</bold> Posterior quadratus lumborum block (QLB) is an inter-fascial plane block that generates both sensory and visceral analgesia with variety of dermatomal coverage, lasting up to 48 h. Most randomized controlled trials of posterior QLB have been limited to cesarean section and gynecological, laparoscopic, and hip surgeries. However, only a few case reports and retrospective studies have described posterior QLB in open colorectal surgery and its efficacy remains controversial. Therefore, this study aimed to assess the analgesic effects of posterior QLB in open colorectal surgery. <bold>Methods</bold> In this prospective, randomized, and controlled trial, 44 patients undergoing elective open colorectal surgery were randomized to receive standard multimodal analgesia alone (control group, n = 22) or in combination with posterior QLB (n = 22). The primary outcome was 24-h cumulative morphine consumption postoperatively. Secondary outcomes included 48-h cumulative morphine consumption, postoperative pain score, time to first analgesic requirement, side effects associated with posterior QLB and morphine, quality of recovery measured by the Thai QoR-35 questionnaire, postoperative clinical recovery, and patient satisfaction. <bold>Results</bold> Cumulative morphine consumption was lower in the QL group than the control group at both 24 h (29.89 ± 5.81 mg vs. 37.41 ± 5.31 mg, P &lt; 0.001) and 48 h (37.16 ± 7.78 mg vs. 47.09 ± 6.88 mg, P &lt; 0.001) postoperatively. Time to first morphine requirement was significantly longer in the QL group than the control group (62.05 ± 28.31 min vs. 25.68 ± 10.61 min, P &lt; 0.001). Both the Thai QoR-35 scores and patient satisfaction scores were not significantly different. <bold>Conclusions</bold> Posterior QLB significantly reduced morphine consumption at 24 h and 48 h postoperatively in patients undergoing elective open colorectal surgery. <bold>Trial registration: The study was registered in the Thai Clinical Trials Registry (TCTR) on www.thaiclinicaltrials.org</bold> on 24 ^th Aug 2021 (registration number:TCTR20210824009). </p>