Anesthesia for Spinal Surgeries

Spinal surgeries involve procedures like spinal decompression, discectomy, spinal fusion, scoliosis correction, and tumor excision. These surgeries often require spinal cord monitoring and controlled hypotension to improve surgical conditions and reduce blood loss.

1. Preoperative Considerations

✅ History & Examination

• Neurological status → Baseline motor and sensory deficits

• Risk factors → Anemia, bleeding disorders, cardiac conditions

• Airway assessment → Cervical spine surgeries may require awake fiberoptic intubation

✅ Investigations

• Hemoglobin, coagulation profile (Risk of bleeding)

• Electrolytes, renal function (If long surgery with fluid shifts)

• MRI, CT scan of the spine

✅ Medication Management

• Continue antihypertensives (Controlled hypotension planned)

• Stop anticoagulants as per protocol

• Steroid coverage (For chronic spinal cord compression patients)

2. Intraoperative Considerations

A. Choice of Anesthesia

✅ General Anesthesia (GA) with endotracheal intubation

✅ Total Intravenous Anesthesia (TIVA) preferred if spinal cord monitoring used

🚫 No N₂O (Expands air pockets, worsens dural tears)

B. Airway & Patient Positioning

✅ Airway Management

• Cervical spine injury → Awake fiberoptic intubation preferred

• Lumbar surgeries → Standard intubation

✅ Positioning

• Prone position (Most common) → Risk of pressure ulcers, venous congestion, airway edema

• Mayfield head clamp (For cervical spine surgeries)

• Lateral or sitting position (Less common)

🚨 Complications of Prone Position

• Hypotension (Venous pooling)

• Facial/airway edema (Prolonged prone position)

• Ophthalmic complications (Ischemic optic neuropathy – ION) → Maintain MAP > 65 mmHg

C. Spinal Cord Monitoring

Neurophysiological monitoring is used to detect early spinal cord injury.

✅ 1. Somatosensory Evoked Potentials (SSEPs)

• Assesses dorsal column function (Proprioception, vibration)

• Affected by volatile anesthetics (>0.5 MAC)

• TIVA (Propofol + Remifentanil) preferred

✅ 2. Motor Evoked Potentials (MEPs)

• Assesses corticospinal tract (Motor function)

• Highly sensitive to inhalational agents and muscle relaxants

• Avoid muscle relaxants after induction

✅ 3. Electromyography (EMG)

• Detects nerve root irritation during pedicle screw placement

• Requires minimal sedation

🚨 Monitoring Changes & Intervention

• Decrease in amplitude or increase in latency → Indicates spinal cord ischemia

• Increase BP, correct anemia, ensure normoxia, normothermia

D. Controlled Hypotension

Why? Reduces blood loss and improves surgical field visibility.

✅ Ideal MAP: 60–70 mmHg

✅ Methods

• Beta-blockers (Esmolol, Labetalol)

• Vasodilators (Sodium nitroprusside, Nitroglycerin)

• Propofol & Remifentanil infusion

• Desflurane, Sevoflurane (Low dose ≤ 0.5 MAC)

🚨 Contraindications

• Severe cardiovascular disease

• Renal dysfunction

• Elderly patients (Risk of spinal cord ischemia)

E. Fluid Management

• Balanced crystalloids (Ringer’s lactate) preferred

• Avoid excessive fluids (Risk of airway edema in prone position)

• Colloids/blood transfusion if major blood loss (>500 ml)

F. Temperature & Coagulation Monitoring

• Maintain normothermia (Hypothermia affects coagulation & SSEPs)

• Coagulation profile monitoring in major spine surgeries

3. Postoperative Considerations

✅ Smooth Emergence

• Avoid coughing, straining → Risk of hematoma, CSF leak

• Consider extubation in a semi-sitting position (Reduces airway edema)

✅ Post-op Pain Management

• Multimodal approach (IV Paracetamol, NSAIDs, Opioids, Epidural Analgesia)

• Avoid excessive opioids (Risk of respiratory depression)

✅ Complications

• Neurological deficits → Check motor & sensory function post-op

• Spinal hematoma → Sudden weakness → Urgent MRI, surgical decompression

• Hypotension due to blood loss → Fluid resuscitation, vasopressors

MCQs for Practice

1. Which of the following anesthetic agents is preferred for spinal surgeries with motor evoked potential (MEP) monitoring?

a) Sevoflurane

b) Propofol

c) Isoflurane

d) Ketamine

✅ Answer: b) Propofol

2. What is the most common complication of prone positioning in spinal surgery?

a) Hypotension

b) Venous air embolism

c) Laryngospasm

d) Hypothermia

✅ Answer: a) Hypotension

3. Why is controlled hypotension used in spinal surgery?

a) To prevent spinal cord ischemia

b) To improve visualization and reduce blood loss

c) To decrease cerebrospinal fluid (CSF) pressure

d) To enhance muscle relaxation

✅ Answer: b) To improve visualization and reduce blood loss

Viva Questions

1. What are the anesthetic goals for spinal surgeries?

2. How do volatile anesthetics affect spinal cord monitoring?

3. What measures can be taken to prevent ischemic optic neuropathy (ION) in prone positioning?

4. Why is TIVA preferred for spinal surgeries with neurophysiological monitoring?

5. What are the complications of controlled hypotension?