Ultrasound-Guided PECS II Block With the patient in a supine position, her arm in a neutral position, and under complete aseptic technique, a 6 to 13 MHz ultrasound linear transducer probe (Mindray, Shen zhen, China) will be positioned below the distal one-third of the clavicle to visualize the pectoralis major and minor muscles, SAM, pectoral branch of the thoracoacromial artery, the second and third ribs, and the external intercostal muscles between the ribs. The needle will be inserted in-plane in a medial-to-lateral direction until its tip is placed between the SAM and the external intercostal muscles. The first injection will be done below the SAM using 20 mL bupivacaine 0.25% at the level of the second rib to block the intercostobrachial nerves and the lateral branches of the third to the sixth intercostal nerves. The needle will be withdrawn until its tip is placed between the pectoralis major and minor muscles, and an additional 10 mL of bupivacaine 0.25% will be injected.

The analgesic efficacy of PECS II-PIFB versus SAPB in patients scheduled for MRM by the total analgesic consumption (nalbuphine in mg) during the first 24 hours.

postoperatively, the numeric rating scale (NRS) for pain assessment during rest and ipsilateral arm movement