The Goal of This Study is to Evaluate the Effect of Ultrasound Guided Erector Spinae Plane Block on Postoperative Pain After Major Abdominal Surgeries

Aim of the work To evaluate the efficacy of ultrasound-guided erector spinae plane block for management of postoperative pain in patients undergoing major abdominal surgery under general anesthesia. Hypothesis * Null hypothesis: The investigators suppose that ultrasound-guided erector spinae plane block has no post-operative analgesic effect in patients undergoing major abdominal surgery. * Alternative hypothesis: The investigators suppose that ultrasound-guided erector spinae plane block has post-operative analgesic effect in patients undergoing major abdominal surgery. Study objectives Primary Objective: Comparison of opioid consumption in patients receiving erector spinae plane block in relation to control group. Secondary Objective: 1. Evaluate the hemodynamics (blood pressure, heart rate) and respiratory rate in patients receiving erector spinae plane block during postoperative period at 0, 2, 4, 6, 8, 12,24 hours. 2. Assessment of numeric rating scale (NRS) in patients receiving erector spinae plane block during rest and movement during postoperative period at 0, 2, 4, 6, 8, 12,24 hours.