The Efficacy of Ultrasound-Guided Rhomboid Intercostal Block Versus Serratus Plane Block in Mastectomy.

While the patient is in the supine position, the arm will be abducted, the ultrasound probe will be placed over the mid-clavicular region of the thoracic cage in sagittal plane. Ribs will be counted until the fifth rib will be identified in the midaxillary line. the latissimus dorsi (superficial and posterior ), teres major (superior), and serratus muscle (deep and inferior)will be identified overlying the fifth rib. As an extra reference point, thoracodorsal artery will be used, this aids in the identification of the plane superficial to the serratus muscle, 30 ml 0.25 %bupivacaine will be injected between latissimus dorsi and serratus anterior muscles at the level of the 5th rib in the mid axillary line.

In the rhomboid intercostal nerve block (RIB) group, the patient will be placed in a lateral position with the affected breast at the top. The ipsilateral arm will be extended to the same level as the ipsilateral chest and breast, and the scapula will be moved outward. On the oblique sagittal plane, a high frequency (6-12MHz) linear ultrasound probe will be placed on the medial edge of the scapula. The US landmarks, trapezius muscle, rhomboid muscle, intercostal muscles, pleura, and lung will be identified. Under the aseptic condition, a 22-gauge needle will be inserted in the plan to the US probe at T5 to T6 levels. Then, 0.25% bupivacaine (30 mL) will be injected into the inter-fascial plane between the rhomboid major muscle and the intercostal muscle, the diffusion of bupivacaine in the fascia between the rhomboid muscle and the intercostal muscle will be visualized. Then, the patient will be positioned in supine position.