The aim of this study is to compare the analgesic effect of bilateral US-guided ESPB using bupivacaine alone versus bupivacaine and DEX in lumbar fusion surgeries.

Surgical treatment of adult lumbar spinal disorders is associated with a substantial risk of perioperative complications. The improvement in management and the development of new techniques in anesthesia and surgical sciences have led to substantial reduction of complications related to lumbar spine surgeries.

Understanding these complications is important and valuable for both the patient and the surgeon. Nevertheless, complications represent undesirable consequences of lumbar spine surgery in adult patients.

Degenerative lumbar disease is one of the most common chronic diseases worldwide. The general incidence of lumbar stenosis accompanied by a significant deterioration in the quality of life reaches 5 % among patients aged < 50 years and approximately 10 - 15 % among elderly patients (50 - 70 years old) Moreover, lumbar stenosis appears to be one of the most common causes of decompression and fusion interventions in the lumbar spine in > 50 years old patients Lumbar surgeries refer to any type of surgical intervention involving any lumbar spine or lower back (between one or more of the L1 - S1 level), including operations for trauma and deformity. The complexity of procedures leads to an increase in comorbidities Major lumbar spine surgery causes severe postoperative pain, which typically persists for at least three days Risk factors most frequently associated with mortality include but are not limited to patients' age, sex, and comorbidity status Postoperative pain is one of the most troublesome pains for the surgical patients and is one of the causes of morbidity and prolonged hospital stay. Various studies have reported that maximal pain occurs in the first 4 postoperative hours and gradually declines by the third postoperative day .

Opiates and non-steroidal anti-inflammatory drugs have been routinely used across the world. Recent resurge of regional anesthetic techniques offer some advantages, especially reduced postoperative nausea and vomiting and less sedation .

Ultrasound (US)-guided erector spinae plane blockade (ESPB) was first developed by Forero in 2016 as an easy and safe way of managing thoracic neuropathic pain. Since that time, this block has gained in popularity and has been used to effectively provide analgesia for a variety of surgeries, including spine surgery .

Erector spinae plane blockade may also have a better safety profile when compared with neuraxial analgesia, perhaps because of direct visualization of the needle under ultrasonography guidance and the ease of placement, although this has not been decisively proven One disadvantage of this block is the short duration of action after a single injection Dexmedetomidine (DEX), is a highly selective and potent central alpha-2 adrenergic receptor agonist. Administration of this adjuvant in miscellaneous methods has received considerable attention in recent years Due to its analgesic and sedative effects, besides the lack of any respiratory-sparing effects, administration of this adjuvant is effective in reducing the need for opioids in the perioperative period and may even result in cooperative sedation.

The neuraxial administration of dexmedetomidine has nociceptive effects on somatic and visceral pains. It also reduces postoperative pain and prolongs analgesia.

Local anesthetic combined with DEX has been reported to prolong analgesia following several blocks. However, it is presently unclear whether adjuncts such as DEX will significantly prolong the duration of ESPB in lumbar fusion surgery.

Oxidative stress is a condition caused by an imbalance between the production and accumulation of reactive oxygen species (ROS) and the body's ability to detoxify these products.

An excess of ROS causes damage to all cellular components. The process of oxidative stress causes the peroxidation of lipids and proteins, the formation of lipid peroxides, DNA fragmentation, and the development of cell death.

ROS activity is usually assessed indirectly by measuring stable products derived from the interaction of these radicals with cellular components. The most-studied cellular antioxidants are superoxide dismutase (SOD) , glutathione peroxidase 1 (GPX1) and human malondialdehyde (MDA).

These enzymes provide the first line of defense against tissue damage caused by ROS. As part of the antioxidant pathway, SOD accelerates the conversion of superoxide to H2O2, while catalase and GPX convert H2O2 to water. SOD and GPX can be measured in serum or plasma to establish the levels of oxidative stress and antioxidant capacity of the body.

Inclusion Criteria:

• Patients of both genders
• age between 18-65 years
• American Society of Anesthesiologists (ASA) physical status I-II**
• scheduled for lumbar spine fusion surgeries ( 2 or 3 level lumbar fusion with or without decompression ) under general anesthesia .

Exclusion Criteria:

• Patient refusal.
• Patient with chronic use of opioid analgesia.
• Uncooperative patients with communication difficulties, which might prevent a reliable postoperative assessment.
• Contraindication to regional anesthesia (bleeding disorder, use of any anticoagulants, local infection).

Known allergy to local anesthetics.