Different Volumes of Local Anesthetics in Thoracolumbar Interfascial Plane Block

A curvilinear array ultrasound probe (Siemens ACUSON X300 Ultrasound System) will be placed at the targeted lumbar level.The corresponding spinous process and interspinal muscles will be identified, and the probe will be slided laterally to identify the longissimus muscle and iliocostalis muscle. Under ultrasound guidance, A 38-mm 22-gauge (22-G, 50-mm 'Stimuplex; BBraun, Melsung, Germany) regional block needle will be advanced in plane to the ultrasound beam in a medial to lateral orientation through the belly of longissimus muscle toward the iliocostalis muscle. Hydro-dissection with 2-3 ml of isotonic saline solution will confirm the correct needle tip position and, after negative aspiration, 0.25 % bupivacaine will be injected slowly whilst carefully monitoring the spread of local anesthetic into the fascial plane between the longissimus and iliocostalis muscles. The same procedure will be repeated on the contralateral side.

"Induction:~Induction of general anesthesia will be performed using a regimen of IV 2 μg/kg fentanyl and propofol IV 2 mg /kg. Tracheal intubation will be facilitated using 0.5 mg/kg IV of atracurium.~Maintenance:~Anesthesia will be maintained with inhaled isoflurane 0.8% in oxygen enriched air (FiO2=0.5). Maintenance doses of 0.1 m\\kg atracurium will be provided every 30 minutes. Then the patient will be placed in prone position."

patients will receive single shot of bilateral modified thoracolumbar interfascial plane block at the mid-level of the operative intervention with 20 ml 0.25%bupivacaine (10 ml on each side).

patients will receive single shot of bilateral modified thoracolumbar interfascial plane block at the mid-level of the operative intervention with 40 ml 0.25%bupivacaine (20 ml on each side).