The aim of the study is to evaluate the difference of postoperative analgesic effects and opioid consumption between ultrasound-guided unilateral oblique subcostal, posterior, or dual TAP blocks in patients undergoing laparoscopic cholecystectomy for cholelithiasis.

Laparoscopic cholecystectomy is one of the most frequent operations. Laparoscopic cholecystectomy is a less invasive technic that provides early mobilization and reduces hospitalization time thus preferred to laparotomy often. There is a minimum of 4 trochar incisions on the right side of the abdomen at epigastric, umbilical, midclavicular subcostal, and anterior axillary subcostal regions in laparoscopic cholecystectomy. Some patients have a drainage tube at the middle/lower right abdomen. Thus the right side of the abdomen is the target side for abdominal wall blocks.

Most patients complain of moderate pain after surgery which requiring opioids, mostly in the upper abdomen, lower abdomen, and shoulder. The pain has three components; somatic pain at the anterior abdominal wall, visceral pain caused by pneumoperitoneum and referred shoulder pain. Preventing postoperative pain is important for reducing respiratory complications and hospitalization time also improve patient satisfaction. Opioids are preferred less due to their side effects like nausea-vomiting and respiratory depression although which is preferable for moderate and severe pain. Transversus abdominis plane (TAP) block is the most preferred abdominal wall block to provide effective postoperative pain control for reducing perioperative analgesic requirements like opioids.

TAP block was first described by Rafi by anatomic landmark technic then by Hebbard with ultrasonographic guidance. TAP block is a regional technic and a plan block that blocks the thoracolumbar nerves that innervate the anterior and lateral abdominal wall and passes in between the muscles' internal oblique and transversus abdominis. External oblique, internal oblique, and transversus abdominis muscles are displayed sequentially by ultrasonography. A hypoechoic, spindle-shaped separation of the fascia by hydrodissection technic is performed by local anesthetic injection in between the internal oblique muscle (or rectus abdominis) and transversus abdominis muscle. Dermatomal spread is differentiated with subcostal, oblique subcostal, and posterior approaches.

In oblique subcostal TAP block, anesthetic solution spreads across the location of T6-L1 nerves thus suitable for surgeries at both superior and inferior the umbilicus. Some other studies show that posterior TAP block can block the T5 to L1 thoracolumbar nerves thereby spreading into paravertebral space. The paravertebral spread of the posterior TAP block suggests that the analgesic efficacy will be long-lasting by blocking the thoracolumbar sympathetic chain and will spread to a wider dermatomal area. In this study, the investigators aimed to compare the analgesic efficacy and opioid-sparing effects of oblique subcostal, posterior, and dual TAP blocks in patients undergoing laparoscopic cholecystectomy. Taking the advantage of the paravertebral extension of the posterior approach and the wide spread of the oblique subcostal approach on the anterior abdominal wall, it's supposed to be the dual TAP block will result in lower pain scores.

All patients will have general anesthesia. For premedication midazolam 0.03mg/kg will be used for all patients. At the induction of the anesthesia, patients will receive propofol 2 mg/ kg, fentanyl 2 μg/kg, and rocuronium 0.6 mg/ kg IV. After enough muscle relaxation patients will be orotracheally intubated. General anesthesia will be maintained with sevoflurane and air/O2 mixture. The end-tidal carbon dioxide partial pressure will be maintained between 32 and 36 mmHg by adjusting the pressure-controlled mechanical ventilation. All patients will receive tramadol 1mg/kg, paracetamol 1gr, and ondansetron 8mg intravenously before skin closure. Postoperatively ultrasound-guided right oblique subcostal and posterior TAP blocks will be performed on all patients. Postoperatively starting from at the postoperative care unit (0th hour) then 2nd,4th, 6th, 8th, 12th and 24th hours pain intensity by numerical rating scale (NRS) at rest and with motion, sensory dermatomal involvement by pinprick test, Ramsey sedation scales, nausea and vomiting scores, and rescue analgesic medication requirements will be recorded. Besides heart rate, blood pressure, respiratory rate, peripheric oxygen saturation, mobilization time, side effects if there are any will be recorded at the aforementioned hours. Patients with NRS≥4 will receive dexketoprofen 50mg as rescue analgesic medication. If NRS≥7 tramadol 100mg will be administered.

The study will start after getting written informed consent from patients who are informed about the study and potential risks. The study is a prospective, clinical, randomized controlled, quadruple-blinded, and monocenter study. Participation of the 60 patients undergoing laparoscopic cholecystectomy had been planned. Patients will be randomized into three groups of 20 patients each.

Inclusion Criteria:

• Patients undergoing elective laparoscopic cholecystectomy for cholelithiasis
• ASA (American Society of Anesthesiologists) I-II

Exclusion Criteria:

• Patient refusal
• Perforation of the gallbladder
• Patients with acute cholecystitis
• History of the previous gallbladder surgery
• Pregnancy
• Morbid obesity
• Psychiatric disorder
• Epilepsia
• Renal insufficiency
• Coagulopathy
• Patients known allergic to drugs used for study

There is no plan to make IPD (individual participant data) available to other researchers