Ultrasound Guided ESP Block Versus Intrathecal Morphine for Postoperative Analgesia in Major HPB Surgery.

Patients will be turned into the prone position. A high-frequency linear ultrasound probe will be placed in a longitudinal parasagittal orientation 2.5-3 cm lateral to the T8 spinous process. The erector spinae muscles will be identified superficial to the tip of the T8 transverse process. After local infiltration of the needle insertion site with 2-3 ml of 2% lidocaine, a 21G 10 cm needle will be inserted using an in-plane approach in a cranial to caudal direction to contact the T8 transverse process. The location of the needle tip will be confirmed by hydrodissection with 2 mL of lidocaine 2% and visualizing linear fluid spread lifting the erector spinae muscle off the bony shadow of the transverse process on ultrasonographic imaging. A volume of 20 mL of 0.25% Bupivacaine is injected will be injected at this point. The same procedure will be repeated for the opposite side.

Patients will be placed on their right side. An intrathecal injection of morphine 200 μg (0.2 mL of morphine sulfate 1 mg/mL) diluted in 1.8 mL normal saline will be administered at the L3-L4 or L4-L5 level with a 25 G Whitacre spinal needle.