Chapter 105. Spinal Surgery and Neurophysiologic Monitoring

• Evaluation of risk depends on several factors:
  • Elective versus emergent versus staged surgery
  • One versus several vertebral levels
  • Primary versus repeat procedure
• ALL cases of spine surgery associated with:
  • Risk of medullary injury
  • Risk of significant blood loss
  • Rare occurrence of significant venous emboli (beware if PFO)
  • Higher prevalence of chronic pain and drug dependence
• Prone positioning associated with:
  • Cardiovascular instability
  • Positioning injuries: pressure points and nerve damage, rarely rhabdomyolysis
  • Visual loss
  • Difficult access to airway
• Patients with previous high (above T5) spinal cord injury (See Chapter 32)
  • Abnormal autonomic responses (hypertensive crisis or hypotension and bradycardia)
  • Vasoplegia (relative hypovolemia)
  • Atelectasis from inefficient cough and/or hypoventilation
  • Bladder spasticity
  • Creatinine does not correlate with renal function
  • Intramuscular injections may have delayed absorption

• Severe scoliosis: assess for MH susceptibility and latex allergy
• Baseline neurologic status: document any preexisting neurologic deficit, look for symptoms appearing during/exacerbated by neck motion (especially in presence of rheumatoid arthritis or spinal stenosis with cervical myelopathy)
• Discuss type of neuromonitoring with surgeon and specialized personnel
• Baseline visual status: document any preexisting visual defect
• Cardiopulmonary comorbidities and physiological reserve
  • Noninvasive cardiac testing in patients with major AHA/ACC risk factors, or intermediate AHA/ACC risk factors and limited exercise tolerance
  • Risk of blood loss: blood work (Hb/Hct, platelets, PT/PTT, ABO typing), assess vascular access, order blood products if necessary
  • Severe scoliosis with pulmonary HTN: obtain baseline ABG and PFTs, look for cor pulmonale, possible need for postoperative ventilation
  • Anti-hypertensive drugs: no ACEIs and/ARBs the day of surgery; no diuretics the day of surgery if history of orthostatic hypotension
• Diffuse articular disease
  • Assess ROM in neck and TMJ (high incidence of difficult airway)
  • Assess ROM in limbs (risk of difficult positioning)
• Chronic pain and drug dependence: consider placement of epidural catheter by surgeon during procedure and specialized pain consultation
• Anticipate need for ICU after surgery
• All patients should receive following information:
  • Risk of neurologic injury, importance of neurologic evaluation immediately after surgery (ETT sometimes still in place), rare necessity to perform wake-up test during procedure (patient maintained in prone position)
  • Risk of blood loss, possible necessity to transfuse blood products
  • If prone position: risk of visual loss (see postop complications Chapter 62)
  • If long procedure (>6 hours), especially if prone and/or cervical, possible necessity to maintain sedated after surgery with ETT in place until safe to extubate
  • If awake fiberoptic intubation: give usual information
  • If major surgery in elderly patient: risk of postoperative cognitive dysfunction

Before induction:

• Prone positioning: make sure specialized table is available with adequate padding
• Usual GA setup plus two large-bore IV lines, A-line, CVL if patient with limited reserve or if high risk of venous air embolism, Foley
• Hemodynamic monitoring to guide fluid administration or if high risk of blood loss
• Have vasopressors, fluid warmers, and blood transfusion sets available. Consider intraoperative blood salvage techniques

Induction:

• Awake fiberoptic intubation if limited cervical and/or temporo-mandibular ROM
• Low-pressure ETT cuffs ...