Prospective, Randomized Study Bariatric surgery has been widely used in the treatment of obesity in recent years. It has been shown to be effective in reaching the ideal weight and reducing obesity-induced comorbidities. Laparoscopic sleeve gastrectomy (LSG) is defined as the first-step bariatric surgery for patients in the high surgical risk group. It has been shown that the laparoscopic approach has lower complication rates, shorter hospital stays, and earlier mobilization compared to open surgery. However, postoperative pain management is very important because it might cause major morbidity, especially pulmonary complications in the early postoperative period.

General recommendations for bariatric surgery include multimodal analgesia without sedatives, local analgesic infiltration, and early mobilization. Opioid analgesics are often preferred for pain management because of their strong analgesic potentials. However, opioids have undesirable adverse effects such as sedation, dizziness, constipation, nausea, vomiting, physical dependence and addiction, hyperalgesia, immunologic and hormonal dysfunction, muscle rigidity, tolerance, and respiratory depression. The morbidly obese patients treated with opioids experience increased risk for adverse effects such as atelectasis, which causes postoperative pulmonary complications, and obstructive sleep apnea, which causes hypoxemia, postoperative ileus and longer hospital stay due to nausea and vomiting. For this reason, in 2006, the American Society of Anesthesiologists (ASA) suggested minimizing or avoiding opioids during perioperative and/or postoperative pain management to the bariatric patients. Therefore, ASA recommends the use of multimodal analgesia including local anesthesia, regional anesthesia and nonsteroidal anti-inflammatory drugs (NSAIDs).

The ultrasound (US) guided erector spina plane (ESP) block is a novel interfacial plan block defined by Forero et al. at 2016. ESP block provides thoracic analgesia at T5 level and abdominal analgesia at T7-9 level. The ESP block contains a local anesthetic injection into the deep fascia of erector spinae. This area is away from the pleural and neurological structures and thus minimizes the risk of complications due to injury. Visualization of sonoanatomy with US is easy, and the spread of local anesthesic agents can be easily seen under the erector spinae muscle. Thus, analgesia occurs in several dermatomes with cephalad-caudad way. Cadaveric studies have shown that the injection spreads to the ventral and dorsal roots of the spinal nerves and creates sensory blockade in both posterior and anterolateral thorax. In the literature, it has been reported that ESP block provides effective analgesia after ventral hernia repair surgery in a randomized controlled study. In some case series and case reports it has been reported that ESP block provides effective analgesia after abdominal and bariatric surgeries. In the literature, there is not still any randomized study evaluating ESP block efficiency for postoperative analgesia management after laparoscopic sleeve gastrectomy surgery.

The aim of this study is to evaluate the efficacy of US-guided ESP block for postoperative analgesia management following laparoscopic sleeve gastrectomy. The primary aim is to compare postoperative opioid consumption and the secondary aim is to evaluate postoperative pain scores (VAS), adverse effects related with opioids (allergic reaction, nausea, vomiting).