Bi-level Erector Spinae Plane Block and Pre-emptive Oral Tizanidine for Analgesia After Mastectomy Surgery

Block will be performed unilaterally with the patient in the sitting position leaning forward. The block will be done using a high frequency linear probe (6-13 MHz). The block area will be adequately sterilized and draped, then the ultrasound probe will be placed 2-3 cm laterally from the midline at the level of the T3 spinous process using a sagittal approach to identify the hyperechoic transverse process shadow deep to the trapezius, rhomboid major, and erector spinae muscles. Then, the needle will be inserted craniocaudally in-plane to reach the transverse process deep to the erector spinae muscle. Correct positioning of the needle will be confirmed through real-time visualization of 2-mL saline hydro dissection. After confirmation of needle position, 15 mL of bupivacaine 0.25% will be injected at each level. The same procedure was repeated for the second level T5 spinous process. block failure defined as the presence of full sensation after 30 minutes, patients will be excluded .

One hour prior to anesthesia induction, the patients will recieve oral placebo capsule that will have the same color, smell, and size as tizanidine.

One hour prior to anesthesia induction, the tizanidine group will receive a 4 mg tizanidine oral capsule.