(30 patients) will receive bilateral ultrasound guided erector spinae plane block using plain bupivacaine 100 mg diluted to volume using normal saline to achieve 50% concentration ( 50 mg plain pubivicaine in each side ).

(30 patients) will receive 0.1 mg /kg of intravenous morphine diluted to 10 ml volume using saline at the end of the operation.

The erector spinae block is achieved by injecting the local anesthetic solution (with possible adjuvants) between the erector spinae muscles (iliocostalis, longissimus, spinalis/ from lateral to medial) and the transverse process .

The technique is performed under ultrasound guidance.

The study will include 60 adult patients undergoing uncomplicated spine surgery under general anesthesia.

At the end of operation , Patients will be randomly divided using closed enveloped method into two equal groups.

• Group 1, (30 patients) will receive bilateral ultrasound guided erector spinae plane block using plain bupivacaine 100 mg diluted to volume using normal saline to achieve 50% concentration ( 50 mg plain pubivicaine in each side ).
• Group 2, (30 patients) will receive 0.1 mg /kg of intravenous morphine diluted to 10 ml volume using saline at the end of the operation.

postoperative pain assessment according to visual analogue scale ( VAS ) within 24 hours after the surgery.

0 - 3 mild pain ( better outcome )

4 - 6 moderate pain

7 - 10 severe pain

> 10 unbearable pain ( worst outcome)

use of intravenous morphine is mostly followed by undesirable side effects such as postoperative nausea and vomiting,urine retention and constipation.

so the target of this study is to show that if ESPB is more preferrable to IV morphine as regard both : postoperative anagesia and avoidance of side effects of systemic morphine.

patients of morphine group will be asked about having nausea or vomiting after surgery and over 24 hours after the operation.