Comparison Between Serratus Anterior Plane Block and Erector Spinae Plane Block to Control Postmastectomy Pain

Serratus anterior plane block was performed in the supine position placing the ipsilateral upper limb in abduction 90 degrees position. Aiming to find the serratus anterior muscle the investigator identified the fifth rib in the mid-axillary line by the linear probe in the sagittal plane. The latissimus dorsi muscle (superficial and posterior), teres major muscle (superior) and serratus muscles (deep and inferior) were detected using ultrasound. The investigator penetrated the serratus anterior muscle by a 25 GA, 90 mm spinal needle in-plane concerning the ultrasound probe from superoanterior to posteroinferior to inject deep to it.

Erector spinae plane block was performed at lateral decubitus with the operation site up, the vertebrae were counted from cephalad to caudal direction until reaching T5 spinous process as the first palpable spinous process is C7. The ultrasound probe was placed vertically 3 cm lateral to the T5 spinous process. Three muscles were identified superficial to the hyperechoic transverse process shadow as follows: trapezius, rhomboid major, and erector spinae. The needle was introduced from superior to inferior direction in-plane until the tip lay deep to erector spinae muscle.