Patients in Group I received a preoperative bilateral ultrasound-guided erector spinae plane block (ESPB) with 20 ml of 0.25% bupivacaine hydrochloride (prepared by combining 10 ml of 0.5% bupivacaine hydrochloride with 10 ml of saline) for each side.

Patients in Group II received a preoperative bilateral ultrasound-guided erector spinae plane block (ESPB) with 30 ml of 0.25% bupivacaine hydrochloride (prepared by combining 15 ml of 0.5% bupivacaine hydrochloride with 15 ml of saline) for each side.

The ESPB will be performed at the T8-T9 vertebral levels. Patients will be placed in the prone position, and skin preparation will be performed with 10% povidone-iodine. Local anesthesia of the skin and subcutaneous tissue will be provided with 3 ml of 2% lidocaine at the target injection site.

Under ultrasound guidance, a sterile-covered linear probe (8 MHz) will be used to visualize the T8 spinous process in the horizontal plane at the midline. The probe will then be rotated to the longitudinal plane, approximately 3 cm lateral to the midline, to visualize the transverse process and the overlying erector spinae muscle. A 22-gauge, 80-mm block needle will be advanced in-plane in a cranio-caudal direction until it contacts the transverse process. The needle was then withdrawn slightly, and its placement between the erector spinae muscle and the transverse process was confirmed through hydrodissection. The patients in Group I received 20 ml of 0.25% (2.5 mg/ml) bupivacaine hydrochloride

The total amount of morphine (in milligrams) consumed by the patient via the Patient-Controlled Analgesia (PCA) device.

Pain intensity measured at rest and during movement (dynamic) using a scale from 0 (no pain) to 10 (worst possible pain).