Comparison of the Efficacy of One Level and Tow Level of Bilateral Thoracic Erector Spinae Plane Block Combined With General Anesthesia in Laparoscopic Bariatric Surgery for Obese Patients: Randomized Controlled Trial

using the in-plane approach, in caudal -to- cephalad direction, through the interfascial plane between the Erector Spinae and the underlying transverse process under strict aseptic precautions until the tip is deep to erector spinae muscle. the block will be performed bilaterally by injecting 60 mL of 0.25% bupivacaine (15 mL into each of four site) into the fascial plane between the deep surface of the Erector Spinae muscle and the bilateral transverse processes of the thoracic vertebrae 5 and 10 (at the most lateral part of the transverse process)