This non-randomized controlled study evaluated the efficacy of a right-sided unilateral Transversus Abdominis Plane (TAP) block for postoperative pain management in 60 adult patients undergoing elective laparoscopic cholecystectomy. Participants were equally divided into a control group receiving standard care and an intervention group that received an ultrasound-guided TAP block using 0.25% bupivacaine prior to extubation. While all patients received scheduled paracetamol and dexketoprofen, tramadol was administered as a rescue analgesic for resting pain scores of 5 or higher. The study's primary goal was to compare postoperative pain using the Verbal Numerical Rating Scale (VNRS) at 0, 6, 12, and 24 hours, with secondary outcomes tracking total rescue tramadol consumption, surgical variables, and postoperative complications to determine the TAP block's overall clinical benefit.

This non-randomised controlled study was conducted from May 2023 to July 2023 after receiving approval from the Institutional Ethical Review Board. The study protocol adhered to the ethical guidelines of the Declaration of Helsinki. Prior to surgery, written informed consent was obtained from all participants. The inclusion criteria for this study were as follows: individuals aged 18 years or older, scheduled for elective laparoscopic cholecystectomy to treat cholelithiasis, American Society of Anesthesiologists (ASA) physical status of I or II, with no communication barriers, able to cooperate during the intervention, and understanding the use of relevant assessment scales. The exclusion criteria encompassed the following: individuals with contraindications to nerve block, such as infection at the puncture site; those diagnosed with malignancy; individuals suffering from severe liver and kidney diseases, coagulation dysfunction, or similar conditions; individuals with a history of previous abdominal surgery or trauma; long-term users of sedative and analgesic drugs, or those with addiction to alcohol, sedatives, or analgesics; individuals experiencing chronic pain; those with known allergies to the drugs used in the study; individuals with mental illnesses that interfere with perception and pain assessment; individuals taking analgesics prior to surgery; individuals with a body mass index (BMI) ≥ 35; patients who were converted from laparoscopic surgery to open surgery; perforation of the gallbladder during cholecystectomy; women who are pregnant or breastfeeding, and patients who withdrew their consent at any stage of the study.

According to the results of the study performed by Ozciftci et al. (13) and using the the calculator at https://www.istatistikakademisi.com/sayfa/nicel-verilerde-orneklem-buyuklugu-hesabi.html, the standard effect size was determined as 0.78 with a 5% margin of error and 80% power, and it was deemed sufficient to include n = 26 cases in each group, and for this reason, 30 patients in each group, a total of 60 patients, were included in the study. The patients were equally divided into two groups in order to their administration to the hospital one by one. The control group (Group 1, n=30) consisted of patients who did not receive a TAP block, while Group 2 (n=30) comprised patients who underwent a right-sided unilateral TAP block. One patient who had malignant gallbladder pathology after LC and fou patients who gave missing data or who didn't want to participate in the study excluded during the study and five new patients enrolled.

Throughout the procedure, the study adhered to the established institutional protocol for anesthesia induction, monitoring, and maintenance. All patients underwent a standardized anesthesia induction process (using 2-3 mg/kg of propofol, 0.6-1.2 mg/kg of rocuronium, and 1 μg/kg of fentanyl). Following orotracheal intubation, patients were adjusted to maintain a tidal volume of 8 mL/kg, an Inspiration: Expiration ratio of 1:2, a respiratory rate of 12/min, and an end tidal CO2 level ranging from 30 to 40 mmHg in controlled ventilation mode. Anesthesia Throughout the procedure, the study adhered to the established institutional protocol for anesthesia induction, monitoring, and maintenance. All patients underwent a standardized anesthesia induction process (using 2-3 mg/kg of propofol, 0.6-1.2 mg/kg of rocuronium, and 1 μg/kg of fentanyl). Following orotracheal intubation, patients were adjusted to maintain a tidal volume of 8 mL/kg, an Inspiration: Expiration ratio of 1:2, a respiratory rate of 12/min, and an end-tidal CO2 level ranging from 30 to 40 mmHg in controlled ventilation mode. Anesthesia maintenance was achieved through a mixture of 60% oxygen and 40% air, along with sevoflurane (maintaining a minimum alveolar concentration of 2.5-3.0).

All surgical procedures were performed by two experienced senior surgeons. The surgeries followed a consistent approach. A 10mm incision was made in the midline, 2 cm below the xiphoid, and a 10mm periumbilical incision was made parallel to the pelvis. Two additional 5mm right subcostal incisions were performed for trocar insertion during laparoscopic cholecystectomy. All surgical procedures were conducted using a laparoscopic approach, and the abdomen was insufflated with CO2, with the insufflation pressure limited to 13 mmHg throughout the procedure. If a drain was used during the surgery, it was taken out of the abdomen through the 5mm trocar.

The TAP block was performed during the post-anesthesia phase before extubation. The procedure involved the use of an ultrasound system and a linear ultrasound transducer (6-12 Hz). To perform the TAP block, the linear probe was positioned 2 cm below the xiphoid to locate the rectus abdominis muscle and fascia. Moving the probe in a downward and lateral direction, the external oblique, internal oblique, and transversus abdominis muscles and fascia were identified over the oblique subcostal angle. A 1-2 ml dose of 2% lidocaine was then applied at the insertion site of the peripheral block needle. With the probe in the oblique subcostal position, the peripheral block needle (Braun, Ultra360, 100 mm, Germany) was carefully advanced along the fascia of the transversus abdominis and internal oblique muscles, from the medial to the inferolateral area of the probe. The accuracy of the block area was confirmed by infiltrating 1-2 ml of 0.9% isotonic sodium chloride, resulting in a hypoechoic and biconvex appearance, as described in the research conducted by Lee et al. (14), and 20 ml of 0.25% bupivacaine on the right side of the abdomen, following the administration described in Sahin et al.'s study (15).

Intravenous infusion of Paracetamol 1 g (Perfalgan®, Bristol-Myers Squibb, USA) was given to all patients at three time points: immediately after surgery, at the 6th hour, and at the 18th hour after surgery. Additionally, all patients received routine intravenous administration of dexketoprofen 50 mg (Arveles®, Menarini, Italy), immediately after surgery and at the 12th hour after surgery to manage pain. Verbal Numerical Rating Scale (VNRS) was administered to all volunteers for pain assessment as primary outcome at postoperative 0, 6, 12, and 24 hours, where scores between 0 and 10 could be assigned. If a patient reported a VNRS score of 5 or higher while at rest, they were given Tramadol hydrochloride (Contramal®, Grünenthal, Germany) at a dose of 0.5 mg/kg. The total amount of tramadol consumed after surgery, as well as age, gender, BMI, operation time, the use of a drain, and postoperative complications, were recorded for each patient as scondary outcome.

Inclusion Criteria:

• individuals aged 18 years or older, scheduled for elective laparoscopic cholecystectomy to treat cholelithiasis, American Society of Anesthesiologists (ASA) physical status of I or II, with no communication barriers, able to cooperate during the intervention, and understanding the use of relevant assessment scales

Exclusion Criteria:

• individuals with contraindications to nerve block, such as infection at the puncture site; those diagnosed with malignancy; individuals suffering from severe liver and kidney diseases, coagulation dysfunction, or similar conditions; individuals with a history of previous abdominal surgery or trauma; long-term users of sedative and analgesic drugs, or those with addiction to alcohol, sedatives, or analgesics; individuals experiencing chronic pain; those with known allergies to the drugs used in the study; individuals with mental illnesses that interfere with perception and pain assessment; individuals taking analgesics prior to surgery; individuals with a body mass index (BMI) ≥ 35; patients who were converted from laparoscopic surgery to open surgery; perforation of the gallbladder during cholecystectomy; women who are pregnant or breastfeeding, and patients who withdrew their consent at any stage of the study.