Surgical procedures on the spine and spinal cord are common and are performed for a wide variety of diseases. They range from minimally invasive, single-level decompression to highly complex, multi-stage extensive reconstruction. Operative procedures for degenerative spine diseases and herniated discs are most common in those under 60 years of age. While those over 60 years of age most commonly undergo spine surgery for spinal stenosis

Patients undergoing spine surgery experience severe pain in the postoperative period. Recent studies show that the incidence of acute postoperative pain following spine surgery vary from 30 to 64%. Postoperative pain may also increase morbidity and incidence of complications and prolong postoperative rehabilitation. In addition, it is a risk factor for development of chronic pain syndromes

Postoperative pain is usually treated with oral or intravenous opioids in combination with non-steroidal anti-inflammatory drugs. However, they often results in insufficient pain control and side effects such as respiratory depression, nausea, and vomiting.

Epidural anaesthesia and analgesia have been shown to be superior to intravenous analgesia. The former is better with respect to pain quality, incidence of side effects, pulmonary, cardiac, and gastrointestinal dysfunction. However, it may be associated with hemodynamic instability. Migration of the epidural catheter with unpredictable absorption of the local anaesthetics remains a challenge to the anaesthetists. The Erector Spinae block proved to be efficient in controlling post-operative pain. It is a simple interfascial plane block, published in 2016. It provides effective analgesia for 24 hours in patients undergoing lumbar spine surgery.

Therefore, a prospective, randomized study was designed to compare the analgesic and side effects of the epidural analgesia with the Erector Spinae block in patients undergoing lumbar spine surgery. To our knowledge, this is the first clinical trial that compares the Erector Spinae block with the epidural analgesia in a variety of lumbar spine surgeries.

History will be taken from all patients. Age and then American Society of Anaesthesiologists' (ASA) score will be recorded.

Preoperatively patients' pain score, laboratory investigations as complete blood picture, coagulation profile, liver and renal functions will be recorded. General examination will be carried out with examination of the back to exclude infection at the injection site and anatomical deformities.

Baseline vital signs will be recorded including non-invasive measurement of systolic, mean, diastolic arterial pressures, and heart rate and oxygen saturation.

After inserting an intravenous (IV) access, the patient will be pre-medicated with midazolam in a dose 0.1 mg/kg and metoclopramide in a dose 0.1-0.2 mg/kg.

Upon arrival to the operating room, appropriate monitors (continuous pulse oximetry, electrocardiography and non-invasive blood pressure) will be placed. Then, general anaesthesia will be induced. 1.5 μg/kg fentanyl and 2 mg/kg propofol will be given. Tracheal intubation will be facilitated with 0.5 mg/kg atracurium. Anaesthesia will be maintained using isoflurane in oxygen and air. Additional doses of 0.1 mg/kg atracurium will be administrated every 30 minutes. A urinary catheter will be placed for control of diuresis. the patient will receive either lumber epidural or erector spinae analgesia according to the group randomization.

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

Failed block is defined as increase in heart rate (HR) and mean arterial blood pressure (MABP)>20% from base line with skin incision. This will be treated by 1ug /kg of fentanyl as top-up doses and increasing isoflurane concentration in case of inadequate response to fentanyl.

In case of decrease in MABP>20% from base line, the patient will receive a 500 ml ringer infusion with 5 mg ephedrine. If HR decrease to 45 beats/minute, atropine 0.5 mg will be given.

postoperative nausea and vomiting will be managed with 0.1 mg/kg ondansetron

Inclusion Criteria:

• ASA I, II patients
• Aged 18-60 years
• Undergoing elective lumbar spine decompression and fusion surgery, using the posterior approach, under general anaesthesia.

Exclusion Criteria:

• Patients with severe cardiac diseases as ischemic heart disease, rheumatic valve disorders and cardiomyopathy.
• Contraindication to neuroaxial anaesthesia e.g. patients on anticoagulants, infection at the injection site and coagulopathy
• Hypersensitivity to the local anaesthetics used.
• Patient refusal.
• Neurologic deficits in the form of sensory loss, motor weakness or preexisting pain symptoms due to neurologic diseases apart from back pain associated with the planned operation.
• Patients with previous back surgeries