Major lumbar spine surgeries are associated with significant postoperative pain that may last for days,So In this study, we intend to evaluate if preventive analgesia with a single injection dose of ultrasound guided bilateral erector spinae is a safe and better method of peri-operative analgesia for lumbar spine surgeries than preincisional local field block.

Patients scheduled for lumbar spine surgery will be recruited and a written informed consent will be obtained from patients.

All patients will be assessed clinically and investigated for exclusion of any of the above mentioned contraindications. Laboratory work needed will be: Complete blood count (CBC); prothrombin time and concentration (PT& PC); partial thromboplastin time (PTT); bleeding time (BT); clotting time (CT) , liver function tests and kidney function tests .

● Operating Room preparation & Equipment: The ultrasound used will be curvilinear high-frequency ultrasound transducer (Siemens acuson x300 3-5 MHz ultrasound)

• Methods: General anaesthesia will be induced. 1.5 μg/kg fentanyl based on lean body weight with maximum dose of 200 μg and 2 mg/kg propofol will be given based on total body weight. Tracheal intubation will be facilitated with 0.5 mg/kg atracurium based on ideal body weight.

Volume controlled ventilation will be adjusted to maintain normocapnia . Anesthesia will be maintained by using 1.5% isoflurane in a mixture of oxygen and air (50/50) and atracurium top ups at a dose of 0.1mg/kg every 30 minutes.

Patients will be placed in the prone position on a Relton Hall frame or padded bolsters.

• In group (A): local field block For the preincisional local field block, a 23-gauge needle is used to infiltrate 20mL of local anesthestic mixture of 0.25% bupivacaine and 1%lidocaine adrenaline (1;200000) will be injected in the subcutaneous space and in the paravertebral muscles on each side of the spinous processes of the presumed surgical approach.
• In group (B): Bilateral Ultrasound guided Erector spinae group. The patient will be in the prone position, after skin sterilization, ESP block will be performed at the level of L3. a curvilinear high-frequency ultrasound transducer will be placed sagittal 3 cm lateral to L3 spinous process where a hyperechoic shadow of the transverse process (TP) and erector spinae will be defined. A 22-gauge spinal needle will be inserted in cranial to caudal direction toward TP in plane to the ultrasound transducer until the needle touches the TP crossing the whole muscles. The location of the needle tip will be confirmed by visible normal saline solution separating erector spinae muscle off the bony shadow of the TP on ultrasound imaging. After confirming the needle site, 20 mL of local anesthestic mixture of 0.25% bupivacaine and 1%lidocaine adrenaline (1;200000) will be injected. The procedure will be repeated following the same steps on the other side.

The surgical intervention will be then allowed 20 minutes after finishing the block procedure.

All participants will be given 1 gram of intravenous paracetamol with maximum dose of 4 gm every 24 hour, together with 4 mg ondansetron 10 min prior to the end of surgery for postoperative nausea and vomiting prophylaxis.

Failed block (increase in HR and mean arterial blood pressure (MABP)>20% from base line with skin incision) will be treated by 0.5 ug/kg of fentanyl as top-up doses and increasing isoflurane concentration in case of inadequate response to fentanyl.

After skin closure , the patient will be turned to supine position,then inhalational anesthesia will be discontinued and reversal of muscle relaxation with atropine (0.02 mg/Kg) and neostigmine (0.05 mg/Kg) will be administered intravenous after return of patient's spontaneous breathing .the patient will be extubated awake, Patients will then be transferred to post anesthesia care unit (PACU) for 60 min to complete recovery and monitoring.

• At any time hypotension (defined as a decrease in mean arterial pressure (MAP) >25% from baseline value or systolic arterial pressure (SAP <100 mmHg)) will be treated with 5 mg IV bolus ephedrine and repeated every 3 minutes until the hypotension resolved. Bradycardia (HR <50 beats per minute) will be treated with atropine 0.5 mg IV.
• Rescue analgesia :

Intra operative:

0.5ug /kg of fentanyl as top-up doses at any time if blood pressure and heart rate increased by more than 20% from baseline reading .

Post-operative :

In the PACU ; VAS will be assessed 15 minutes after extubation and if the score is exceeding 4/10 , rescue analgesia in the form of Nalbuphine 0.1mg/kg will be given .another dose of Nalbuphine 0.1mg/kg can be given in the PACU if the score still more than 4 after 30 minutes of the 1st dose.

After discharging from the PACU; the analgesic plan will be intravenous paracetamol 1gm every 8hours and ketorolac 0.5mg/kg/6hours as a standard regimen , Nalbuphine 0.1mg/kg will be given as rescue analgesia on demand or at any time if VAS score exceeding 4(maximum 20mg per dose and 160mg in 24 hours)

Inclusion Criteria:

• Patients 18-65 years old.
• Patients undergoing Lumbar spine surgery (L1-L5).
• American society of anesthesiologists classification (ASA) I and II.
• BMI < 35
• Duration of surgery less than 3 hours

Exclusion Criteria:

• Patient's refusal.
• Bleeding disorders (platelets count < 150,000; INR >1.5; PC< 60%) and coagulopathies.
• Skin lesion, wounds or infection at the injection site.
• Known allergy to local anesthetic drugs.
• Chronic opioid users.
• Patients with pre-operative opioid consumption.
• Patients on long term therapy of Corticosteroids