Although total intravenous anesthesia (TIVA) provides advantages such as accelerated recuperation and diminished postoperative nausea, it also has constraints, such as the potential for hemodynamic instability and inadequate analgesia. TIVA is less suitable for major surgeries, particularly those involving the spine, when used alone, due to these limitations, as they necessitate substantial muscle relaxation and pain management.

A non-competitive antagonist of the N-methyl-D-aspartate (NMDA) receptor, magnesium sulfate (MgSO4), exhibits antinociceptive properties. The infusion of Magnesium during general anesthesia has been shown to decrease the need for anesthesia and the consumption of postoperative analgesics in numerous clinical studies. MgSO4, when utilized as an adjunct to TIVA, has been demonstrated to decrease the duration of extubation, facilitate earlier emergence from anesthesia, and facilitate intraoperative neurophysiological monitoring (IOM) during spine surgery.

Dexmedetomidine is a selective α2-adrenoreceptor agonist whose sedative effects are predominantly mediated by its action on α-2 adrenergic receptors in the brain and spinal cord. It delivers efficient sedation without the pronounced respiratory depression that is frequently observed with other sedatives. Dexmedetomidine induces a profound sense of tranquility and alleviates anxiety by selectively targeting specific receptors in the central nervous system, in addition to offering analgesic advantages. Dexmedetomidine has been employed in the surgical intensive care unit to expedite the extubation process. Dexmedetomidine is now being utilized more frequently as an adjuvant for propofol-based TIVA in procedures that necessitateintraoperative neurophysiological monitoring.

There is a paucity of literature comparing TIVA with magnesium sulphate and TIVA with dexmedetomidine in spine surgeries.

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) physical status I, II.
• Scheduled for elective spine surgery up to two levels under general anesthesia

Exclusion Criteria:

• History of preoperative neuromuscular disease, hepatic impairment [defined as a known diagnosis of liver cirrhosis, hepatitis with elevated liver enzymes (>2 times upper standard limit), or Child-Pugh score B or C], renal impairment [defined as chronic kidney disease with an estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² or history of dialysis], endocrinal disorders [including uncontrolled diabetes mellitus (HbA1c >8.5%), thyroid dysfunction (untreated hypo/hyperthyroidism), or adrenal insufficiency], hematological disorder [such as anemia (Hb <10 g/dL), coagulopathies (INR >1.5, platelet count <100,000/mm³), or bleeding diathesis] or cardiovascular dysfunction [defined as history of ischemic heart disease, arrhythmias requiring treatment, heart failure (NYHA class II or higher), or uncontrolled hypertension (SBP >160 mmHg or DBP >100 mmHg)].
• Any degree of heart block.
• Known allergy to the study drugs.
• Scoliosis surgery.
• Cervical spine surgeries.
• Surgeries with an anticipated duration of more than 4 hours.
• Receiving magnesium supplementation.
• Any Preoperative Disturbed consciousness level or cognitive dysfunction.
• Drugs known to have a significant interaction with NMDAs.
• Chronic use of opioids and current treatment with a β-blocker or calcium channel blocker.