Erector Spinae Plane Block in Spine Surgeries

. The patient will be placed in the prone position. A high-frequency linear probe or a curved array probe, depending on the BMI of the patient, will be placed in longitudinal alignment, 2-3cm lateral to the vertebral column. The transverse processes of the vertebrae at the level of surgery, the erector spinae muscle, and the psoas muscle will be identified. A 5- or 8-cm 22-G ultrasound needle will be inserted with an in-plane technique in a cephalad-to-caudal direction until bone contact with the top of the transverse process is reached. After slight retraction of the needle, 20ml of bupivacaine 0.25% will be injected behind the erector spinae muscle. The same procedure will be repeated on the contralateral side.