Dexmedetomidine as an Adjuvant to Bupivacaine in Ultrasound-guided Pericapsular Nerve Group Block( PENG)

Patients meeting the inclusion criteria will be randomly assigned to receive either:

Group A: PENG block with bupivacaine only (number of patients: 42) Group B: PENG block with bupivacaine and dexmedetomidine (number of patients: 42)

Preoperative assessment:

Preoperative assessment of all patients undergoing elective laparoscopic shoulder surgical procedures under general anaesthesia comprised of history taking, clinical examination, laboratory testing (complete blood count, kidney function tests, and liver function tests), electrocardiogram, and chest X-ray. The study protocol will be explained to the patients, and their consent will be obtained.

The visual analogue score (VAS) will be explained to all patient in details as it will be used as a measurement tool for assessment of postoperative pain

Operating Room preparation & Equipment:

The ultrasound used will be Siemens ACUSON X300 Ultrasound System, the scanning probe is a linear probe 8-14 MHZ. A 50-mm block needle 22 gauge will be used. (SonoPlex Stim Cannula, Germany).

All blocks will be given by one researcher using 20 ml of drug 0.25% bupivacaine either alone or with dexmedetomedine.

After arrival to the anesthetic room, an 18-gauge intravenous cannula will be placed at the forearm contralateral to the operated arm, standard monitoring will be used (non-invasive arterial blood pressure, ECG, pulse oximetry).

Premedication will be given intravenously in the form of 0.03 mg/kg midazolam, ranitidine 2.0 mg/kg IV and metoclopramide 0.1 mg/kg IV).

Patients will be randomly assigned to either the intervention group will receive PENG block with bupivacaine 0.25% and dexmedetomidine 1 µg/kg (maximum dose of 100 µg) diluted in normal saline (total volume of 20 mL) or control group will receive PENG block with bupivacaine 0.25% (20 mL) diluted in normal saline.

PENG block:

The patient will be asked to lie supine with his or her arm then positioned in a 45-degree abducted external rotation. A linear ultrasound probe was placed lengthwise between the coracoid and humeral head. Once the humeral head, subscapular muscle tendon, and deltoid muscle were identified, a 50-mm needle will be inserted using the "in plane" technique. The needle then will be advanced through the deltoid muscle and towards the subscapularis tendon, until a bony-like hard tissue is felt, preventing further advancement of the needle. The needle is placed now between the deltoid muscle and subscapularis tendon in which injection will be done.

Thirty minutes after performing the block patients will receive general anaesthesia. Anaesthesia will be induced with propofol (2 mg/kg), fentanyl (2 μg/kg) and atracurium (0.5 mg/kg). The GA will be maintained by isoflurane (1.2 %) and Atracurium (0.1 mg/kg/20 min). the surgery will then be started and intraoperative vital signs as heart rate, MAP (mean arterial blood pressure) will be monitored all throughout. If at anytime during the operation hypertension and tachycardia were observed, fentanyl 50 mic will be given as an intraoperative rescue analgesia.

After skin closure, muscle relaxation will be reversed using Neostigmine (0.04mg/kg) and Atropine (0.01mg/kg) after the return of spontaneous breathing. After extubation patients will be transferred to the post-anesthesia care unit (PACU) for 60 min for complete recovery and monitoring.

If at any point hypotension occurred (defined as a decrease in mean arterial pressure > 25% from the baseline value or systolic arterial pressure of 100 mmHg), it will be treated with 5 mg of IV bolus ephedrine, which will be repeated every 3 min until the hypotension resolved. Bradycardia (defined as an HR of 40 beats/min) will be treated with intravenous atropine (0.5 mg).

Postoperative vital signs (heart rate and MAP) and VAS for pain will be recorded at 0, 2, 6, 12, 24 hours and if VAS ≥3 or when the patient asks for analgesia, morphine IV (0.1mg/kg) will be given (rescue analgesia) targeting VAS ≤ 2 while the maximum allowed dose of morphine is 30 mg / 24 hours. The time to first call for analgesia is defined as (the time interval from tracheal extubation to first dose of morphine administration) will be recorded. The patient will receive paracetamol (1gm/8hrs IV) as a regular analgesia as soon as he is discharged from the recovery and admitted to the post-operative ward. The total amount of morphine in the first postoperative 24 hours will be calculated in both groups If the patient requires more than two doses of rescue analgesia in the first hour following surgery, the block will be deemed to have failed.

-Post operative haemodynamic will be assessed (heart rate and MAP at the same time point).

Incidence of adverse effects, such as hypotension, bradycardia, and sedation.