Comparative Study Between Ultrasound Guided External Oblique Intercostal Plane Block and Erector Spinae Block for Postoperative Analgesia in Hepatectomy Incision in Cancer Patients

A 20G IV cannula will be inserted. All patients will be premedicated with IV midazolam 0.01-0.02 mg/kg 30 minutes preoperatively. all patients will be monitored continuously using ECG, NIBP, peripheral arterial oxygen saturation and end tidal carbon dioxide throughout the duration of surgery.

Induction of general anaesthesia will be done by propofol 1.5-2 mg/kg, fentanyl 1-2 μg/kg, and atracurium 0.5 mg/kg IV. All patients will receive paracetamol 1 gm by IV drip, ketorolac 30 mg IV drip. Anaesthesia will be maintained by sevoflurane 2%-3% in O2/air mixture with reinjection of atracurium 0.1 mg/kg every 30 minutes. The same procedures will be applied to all patients.

Group 1 - External Oblique Intercostal Block (EOI) Patients positioned in the supine position with their ipsilateral arm abducted. A 12-15 MHz linear transducer (FUJIFILM Sonosite M-Turbo C Ultrasound System) will be used for ultrasonography. With the proceduralist at the patient's ipsilateral shoulder, the chest wall is systematically scanned. Initially the probe is placed in a cephalad to caudad paramedian direction at the anterior axillary line, and the external oblique muscle identified at the level ribs 6 and 7 in line with the xiphoid process. To confirm correct identification of the external oblique muscle, the probe is moved in the caudad direction following the external oblique muscle. At the subcostal level, the ultrasound probe is rotated 90° to see the convergence with the internal oblique and transversus abdominus muscles. The probe is then moved back to the initial identification point for the external oblique muscle. The EOI plane is identified deep to the external oblique muscle and superficial to the sixth and seventh ribs and their associated intercostal muscles. Local anaesthetic is then infiltrated subcutaneously and a 16 G Tuohy needle is inserted cephalad to caudad, and the EOI plane was hydro-dissected with saline,20 ml of local anaesthetic injected (0.25% bupivacaine)(8).

Group 2 - Erector Spinae Block (ESP) The patient in lateral position, then spinous processes were palpated and marked directly on the skin by a dermographic pencil, and the correctness of the final marking was confirmed by sonographic inspection. A 21-gauge, 50 mm needle was inserted with a cephalad-to-caudal direction into the posterior thoracic wall at the T5 level, to reach the respective transverse process.

The proper needle tip positioning was checked by ultrasound guidance with a 12.5 MHz linear probe (FUJIFILM Sonosite M-Turbo C Ultrasound System) the visualization of a linear fluid spread that distended the fascial plane between the erector spinae muscles group and the transverse process while injecting 2 mL of normal saline solution was considered confirmatory.

Subsequently, 20 mL of local anaesthetic injected 0.25% bupivacaine (9).

Intraoperative rescue analgesia of fentanyl 1 μg/kg will be given if the mean arterial blood pressure or heart rate rises above 20% of baseline levels. Ringer acetate will be infused to replace the fluid deficit, maintenance and losses, and the patients will be mechanically ventilated at appropriate settings that keep end-tidal CO2 at 30- 35 mmHg.

The 1st reading of mean arterial pressure (MAP) and heart rate (HR) will be recorded before induction of general anaesthesia to be defined as a baseline reading while another reading will be noted immediately before surgical incision and at 15-minute intervals intraoperatively.

At the end of surgery residual neuromuscular blockade will be reversed using neostigmine (0.05 mg/kg) and atropine (0.02 mg/kg), and extubation will be performed after complete recovery of the airway reflexes.

The patients will be transferred to the post-anaesthesia care unit (PACU) where the Visual Analogue Scale score (VAS), MAP and heart rate will be noted immediately on arrival, and the patients will be observed till fulfilling the criteria of discharge then transferred to the ward where multimodal analgesia will be provided as the following: IV paracetamol 1 g /8 hours and IV ketorolac 30mg/8 hours.

Post-operative rescue analgesia will be provided in the form of IV morphine 0.1 mg per kg if the patient VAS Score ≥ 4. The total amount of morphine given in 24 hours will be recorded for both groups. A maximum dose of 0.5 mg/kg/24hours of morphine is allowed. VAS, MAP, and heart rate will be noted at 1, 6, 12, and 24 hours postoperatively. Side effects of morphine include: nausea, vomiting, sedation, and respiratory depression (respiratory rate <10/minute), and they will be recorded.

Postoperative nausea and vomiting (PONV) will be rated on a four-point verbal scale; (none =no nausea, mild =nausea but no vomiting, moderate=vomiting one attack, severe =vomiting >one attack). 0.1 mg/kg of IV ondansetron will be given to patients with moderate or severe postoperative nausea and vomiting.