Comparison of postoperative analgesia effects between subcostal anterior quadratus lumborum block and transversus abdominis plane block in bariatric surgery: a prospective randomized controlled study.

Background: Currently, the prevalence of obesity is on the rise annually. Bariatric surgery stands out as the most efficacious approach for addressing obesity. Obese patients are more prone to experience moderate to severe pain after surgery due to lower pain thresholds. Regional block, as an important component of multimodal analgesia in bariatric surgery, is crucial in reducing opioid consumption and alleviating postoperative pain in patients undergoing bariatric surgery. Transversus abdominis plane block (TAPB) has gained widespread utilization in bariatric surgery; however, its limitation of inadequate reduction of visceral pain in obese patients remains a significant concern. Therefore, it is imperative to explore new and more efficient strategies for analgesia. Quadratus lumborum block (QLB) has emerged as a popular nerve block in recent years, frequently utilized in conjunction with general anesthesia for abdominal surgery. In the cadaver study of QLB, it was confirmed that the dye level could reach up to T6 when using the subcostal anterior quadratus lumborum muscle approach, which could effectively reduce the incision pain and visceral pain of bariatric surgery patients during the perioperative period. However, there is currently a lack of research on the use of subcostal anterior QLB in patients undergoing bariatric surgery. Our study aims to investigate whether subcostal anterior QLB can provide superior perioperative analgesic efficacy for bariatric surgery under general anesthesia compared to TAPB, leading to reduced postoperative opioid consumption and a lower incidence of postoperative nausea and vomiting (PONV).

Methods and design: This study is a prospective, randomized controlled trial aiming to recruit 66 patients undergoing bariatric surgery. The participants will be randomly allocated into two groups in a 1:1 ratio: subcostal anterior QLB group (n = 33) and TAPB group (n = 33). The study aims to investigate the efficacy of subcostal anterior QLB and TAPB in obese patients who are scheduled to undergo bariatric surgery. Our primary outcome is to observe the amount of opioids used in the two groups 24 h after operation. The secondary outcomes included VAS of pain during rest/activity after operation, the type and dose of additional analgesics, the occurrence and severity of PONV, the type and dose of additional antiemetic drugs, postoperative anesthesia care unit (PACU) time, time of first postoperative exhaust, time to first out of bed activity, time to first liquid diet and postoperative admission days.

Discussion: Opioid analgesics are prone to causing adverse reactions such as nausea, vomiting, and respiratory depression, especially in obese patients. Multimodal analgesia, including nerve block, can effectively reduce the dose of opioids and alleviate their adverse effects. Currently, TAPB is the most prevalent nerve block analgesia method for abdominal surgery. Recent studies have indicated that subcostal anterior QLB offers advantages over TAPB, including a wider block plane, faster onset, and longer maintenance time. It is not clear which of the two nerve block analgesia techniques is better for postoperative analgesia in patients undergoing bariatric surgery. Our objective in this investigation is to elucidate the superior method between TAPB and subcostal anterior QLB for postoperative pain management in bariatric surgery.

Trial registration: ChiCTR ChiCTR2300070556. Registered on 17 April 2023.