direct comparisons between ESPB and M-TAPA for postoperative analgesia after LC remain limited. This is an important area of clinical interest because the two blocks differ significantly in their anatomical targets, mechanism of analgesia, and likely dermatomal coverage. The ESPB provides analgesia through paravertebral spread affecting both dorsal and ventral rami, thereby offering posterior and visceral pain relief, whereas M-TAPA directly targets the thoracoabdominal nerves, resulting in better anterior and lateral abdominal wall analgesia. Understanding which technique offers superior or more balanced analgesia could help to optimise regional anaesthesia strategies in LC and to improve patient outcomes.

Laparoscopic cholecystectomy (LC) has largely replaced open cholecystectomy as the standard surgical treatment for symptomatic gallbladder disease. The minimally invasive approach is associated with significantly less postoperative pain, shorter hospital stay, faster return to normal activity, lower risk of wound infection, and better cosmetic results. (1,2) Despite these advantages, many patients still experience moderate to severe pain in the early postoperative period. This pain results from a combination of somatic pain at trocar insertion sites, visceral pain due to gallbladder bed irritation, and referred shoulder pain from diaphragmatic stretching caused by pneumoperitoneum. (3) Effective postoperative pain control is crucial not only to improve patient comfort but also to reduce opioid consumption, facilitate early ambulation, and decrease postoperative pulmonary complications. (4) Traditionally, postoperative analgesia following LC has relied on multimodal regimens including systemic non-steroidal anti-inflammatory drugs (NSAIDs), opioids, port-site local infiltration, and intraperitoneal local anaesthetic instillation. (5) While opioids remain an important analgesic option, their side effects-such as nausea, vomiting, respiratory depression, pruritus, and delayed recovery-can adversely affect the quality of postoperative recovery. (6) Consequently, there has been increasing interest in the use of ultrasound-guided regional anaesthetic techniques as part of multimodal analgesia to improve pain control and reduce opioid requirements after LC.

Among these regional approaches, the erector spinae plane block (ESPB) has gained significant attention in recent years. The ESPB involves injecting local anaesthetic into the fascial plane deep to the erector spinae muscle, typically at a thoracic vertebral level. This allows cranio-caudal spread and potential diffusion into the paravertebral and epidural spaces, resulting in both visceral and somatic analgesia across multiple dermatomes. (7) 4. It was found that bilateral Erector Spinae Plane Block has shown promising benefits for postoperative analgesia after laparoscopic cholecystectomy which includes, reduction in postoperative pain scores, reduced opioid requirements, improved recovery and improved postoperative respiratory function and these findings highlight ESPB as an effective, safe and easy to perform block for postoperative analgesia after laparoscopic cholecystectomy. (8) A newer alternative regional technique is the Modified Thoracoabdominal Nerve Block through the Perichondrial Approach (M-TAPA). First described by Tulgar et al., this block targets the anterior and lateral cutaneous branches of the thoracoabdominal nerves (T5-T12) by depositing local anaesthetic in the perichondral plane beneath the costal cartilage. (9) Its theoretical advantage lies in providing both anterior and lateral abdominal wall analgesia, which corresponds well to the sites of trocar insertion in LC. Early evidence has been promising and demonstrated that bilateral M-TAPA significantly reduced postoperative pain scores. M-TAPA significantly reduced 24-hour opioid consumption and decreased the incidence of postoperative nausea and vomiting and also shortened hospital stay and improved patient satisfaction following LC.

AIM OF THE WORK To compare the analgesic efficacy of the Erector Spinae Plane Block (ESPB) versus the Modified Thoracoabdominal Nerve Block through the Perichondrial Approach (M-TAPA) for postoperative pain control in patients undergoing laparoscopic cholecystectomy under general anaesthesia.

Primary outcome:

Time to First Analgesic request.

Secondary outcomes:

1. Total Nalbuphine consumption.
2. Visual analogue score (VAS) in the first 24 hours after surgery.
3. Patient satisfaction.
4. Quality of postoperative recovery (QOR 15).
5. Incidence of complications or adverse events.

PATIENTS After approval of the Medical Ethical Committee of the Faculty of Medicine, Alexandria University and having an informed written consent from every patient included in this study, the present study will be carried out in Alexandria University Main Hospital on 50 patients aged between 30 and 65 years, of both sexes, belonging to American Society of Anesthesiologists classes I-III who are scheduled for laparoscopic Cholecystectomy. The study will be designed as a double-blinded, single-center prospective, randomized comparative design. The sample size is approved to be sufficient by the department of statistics, Medical Research Institute, Alexandria University.

By using SPSS program version 28, (12) A minimal total sample size of (34) patients undergoing laparoscopic cholecystectomy (17) per group is needed to detect an assumed difference of (1) (13) in mean visual analogue scale (VAS) between a group of patients receiving erector spinae plane block with an assumed mean of (2.4±1.1) vs another group receiving modified thoracoabdominal nerve block with an assumed mean of (1.4±0.9) to evaluate the efficacy of both procedures regarding pain control after laparoscopic cholecystectomy using independent t test with a significance level of (0.05) and 80% power.

Patient grouping and randomization:

Patients will be randomized by sealed envelope technique into two equal groups (25 patients each):

Group (1): Twenty-five patients will receive bilateral ESP block with injection of 20 ml 0.25% bupivacaine.

Group (2): Twenty-five patients will receive bilateral M-TAPA block with injection of 20 ml of 0.25% bupivacaine.

METHODS For every patient in the study the following will be done.

Preoperative assessment:

1. Proper history taking.
2. Complete clinical examination.
3. Routine laboratory investigations and any other investigation needed.

Patient preparation:

On arrival to the operative theatre, a 20G intravenous cannula will be inserted in a peripheral vein.

The technique of anaesthesia will be explained to the patients. All patients will be premedicated with midazolam 0.05 mg/kg IV.

Monitoring:

Using a multichannel monitor (mindray patient monitor Model (iMEC10) CHINA), the patients will be monitored for:

1. Noninvasive arterial blood pressure.

2. Lead II electrocardiography (for rate and Rhythm).

3. Pulse oxygen saturation (SpO2 %).

4. End tidal CO2 (ETCO2). Standardized general anesthesia will then be induced in both groups.

   Anesthetic technique: Pre-oxygenation will be done for 3 minutes. Induction will be done with propofol 2 mg/kg intravenous (IV), fentanyl 2 μg/kg IV and atracurium 0.5 mg/kg IV to facilitate endotracheal intubation. Then volume control mechanical ventilation will be set, Tidal Volume 8ml/kg of ideal body weight and will be adjusted according to ETCO2 to maintain it between 35-40 mmHg. (15) Anesthesia will be maintained with 1-1.5% Isoflurane in 50% O2 and air. Muscle relaxation will be maintained with atracurium 0.1 mg/kg IV. (16) All patients will receive Dexamethasone (8 mg) intravenously as anti-emetic. (17)

   Regional anesthetic technique:

   After induction of general anaesthesia and prior to surgical incision, patients will be positioned for administration of the regional block according to their assigned study group.

   ● Erector Spinae Plane Block (ESPB) Group o With the patient in the lateral position, using complete aseptic techniques, the T8 spinous process will first be identified in the midline using a high-frequency linear ultrasound probe (Sonosite). The probe will then be moved 2-3 cm laterally to visualize the characteristic hyperechoic shadow of the T8 transverse process, along with the overlying erector spinae muscle.

   Using an in-plane technique, an 18-gauge block needle will be advanced in a cranio-caudal direction until the needle tip contacts the posterior aspect of the T8 transverse process. The correct needle placement will be confirmed by hydrodissection of the interfascial plane with 2-3 ml of 0.9% normal saline, ensuring separation between the erector spinae muscle and the transverse process.

   Following confirmation of correct placement, 20 ml of 0.25% bupivacaine will be injected slowly under continuous ultrasound guidance. The spread of local anaesthetic in the fascial plane, extending cranio-caudally between the erector spinae muscle and the transverse processes, will be observed in real time to confirm adequate distribution.

   The same process will be repeated on the other side.

   ● Modified Thoracoabdominal Nerve Block (M-TAPA) Group

   For patients allocated to the M-TAPA group, the procedure will be performed under similar aseptic and ultrasound-guided conditions, using the same type of needle and concentration of local anaesthetic. With the patient in the supine position, the ultrasound probe will be placed transversely over the costal margin at the T8-T9 level, and the perichondrial plane will be identified beneath the costal cartilage. Using an in-plane approach, the needle will be advanced until the tip reaches the desired plane, and correct positioning will be confirmed by hydrodissection with 2-3 ml of 0.9% saline. Subsequently, 20 ml of 0.25% bupivacaine will be injected, with visualization of local anaesthetic spread beneath the costal cartilage confirming proper deposition.

   The same process will be repeated on the other side. After the completion of surgery, residual neuromuscular blockade will be reversed with neostigmine 0.05 mg/kg and atropine 0.02 mg/kg intravenously. Following full recovery of spontaneous respiration and protective airway reflexes, patients will be extubated and transferred to the post-anesthesia care unit (PACU) for monitoring and postoperative evaluation.

   ● Post-operative management

   All patients will receive intravenous paracetamol 1 g every 6 hours, as well as Ketorolac 30 mg every 12 hours as baseline analgesia in the immediate post-operative period. If the VAS score is equal to or greater than 4, rescue analgesia in the form of intravenous nalbuphine 0.1 mg/kg will be administered and recorded. (16,18)

   Postoperative nausea and vomiting (PONV) will be assessed using a 4-point scale (0 = none, 1 = mild, 2 = moderate, 3 = severe) at the same time intervals as pain assessment. If moderate or severe nausea occurs, intravenous ondansetron 4 mg will be administered as rescue antiemetic therapy.

   Post operative outcomes will be assessed in ward by Doctors who are blinded to patient group assignment and study design.

Inclusion Criteria:

• Age: between 30 - 65
• American Society of Anaesthesiologists physical status: I- III
• Body mass index: 18-35 kg.m-2

Exclusion Criteria:

• Patient Refusal
• Allergy to local anaesthetic agents.
• Skin infection at the site of injection.
• Coagulopathy.
• Diabetes Mellitus