patients will receive bilateral ultrasound guided erector spinae block before the lumbar spine surgery starts.(20ml of bupivacaine 0.25%) after receiving general anesthesia

patients will receive standard general anesthesia for lumbar spine surgery according to hospital protocol.

. 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.

the analgesic effect of erector spine block will be assessed postoperative by numeric rating scale (NRS), if NRS is more than 3 the patient will receive a rescue dose of 5 milligrams of morphine

Measure mean blood pressure of patients postoperative every 4 hours

Measure heart of the patients postoperative every 4 hours