EDAIC Neuroanesthesia and Neuromonitoring 4 — Questions and Answers
Question 1: A patient undergoing spine surgery develops loss of MEP signals bilaterally 30 minutes after distraction. The FIRST response should be:
- Increase the volatile anesthetic to deepen sedation
- Immediately notify the surgeon and consider reducing distraction (Correct answer)
- Administer IV methylprednisolone
- Increase mean arterial pressure with vasopressors
Correct answer: Immediately notify the surgeon and consider reducing distraction
Loss of MEPs during spine distraction suggests cord ischemia or mechanical injury; the surgeon must be alerted immediately to reduce distraction and relieve the insult.
Question 2: Which volatile anesthetic concentration most reliably abolishes MEP signals and should be avoided during spine surgery with neuromonitoring?
- >0.25 MAC
- >0.5 MAC
- >1.0 MAC (Correct answer)
- >1.5 MAC
Correct answer: >1.0 MAC
Volatile agents at greater than 1.0 MAC consistently suppress MEPs to an unmonitorable level, making TIVA with propofol/remifentanil preferable for spine neuromonitoring.
Question 3: Near-infrared spectroscopy (NIRS) monitors cerebral oxygenation in which vascular territory?
- Predominantly arterial (70% arterial, 30% venous)
- Predominantly venous (25% arterial, 75% venous) (Correct answer)
- Pure arterial capillary bed only
- Equal arterial and venous contributions
Correct answer: Predominantly venous (25% arterial, 75% venous)
NIRS measures regional cerebral oxygen saturation (rSO2) in a predominantly venous (75%) compartment, reflecting overall cerebral oxygen supply-demand balance.
Question 4: Which anesthetic technique is associated with the lowest incidence of postoperative cognitive dysfunction (POCD) in elderly patients undergoing major surgery?
- Regional anesthesia alone (Correct answer)
- TIVA with propofol
- Volatile anesthesia with sevoflurane
- Ketamine-based general anesthesia
Correct answer: Regional anesthesia alone
Regional anesthesia avoids systemic effects of general anesthetic agents on the CNS and is associated with the lowest rates of POCD in elderly surgical patients.
Question 5: In a patient with a known intracranial arteriovenous malformation (AVM) presenting for embolization, which hemodynamic concern is specific to AVM resection?
- Intraoperative hypotension from vasodilation
- Normal perfusion pressure breakthrough (Correct answer)
- Cerebral vasospasm from contrast media
- Venous air embolism from sinus proximity
Correct answer: Normal perfusion pressure breakthrough
Normal perfusion pressure breakthrough occurs when chronic hypoperfusion surrounding an AVM is reversed post-resection, causing hyperemia and hemorrhage in surrounding brain.
Question 6: Which CSF finding is characteristic of bacterial meningitis requiring emergent antibiotic therapy?
- Glucose >60 mg/dL, protein 20-45 mg/dL, lymphocytic pleocytosis
- Glucose <40 mg/dL, protein >100 mg/dL, neutrophilic pleocytosis (Correct answer)
- Xanthochromia, elevated RBCs, normal glucose
- Normal glucose, mildly elevated protein, oligoclonal bands
Correct answer: Glucose <40 mg/dL, protein >100 mg/dL, neutrophilic pleocytosis
Bacterial meningitis classically presents with low CSF glucose (<40 mg/dL), high protein (>100 mg/dL), and neutrophilic pleocytosis requiring immediate antibiotics.
Question 7: During craniotomy for supratentorial tumor, which maneuver most rapidly reduces brain bulk to facilitate surgical access?
- Head elevation to 30 degrees
- Mannitol 1 g/kg IV bolus
- Controlled hyperventilation to PaCO2 30-35 mmHg
- Lumbar CSF drainage (Correct answer)
Correct answer: Lumbar CSF drainage
Lumbar CSF drainage provides the most rapid and controlled reduction in intracranial volume and brain bulk, offering direct decompression.
EDAIC Neuroanesthesia and Neuromonitoring 4
A patient undergoing spine surgery develops loss of MEP signals bilaterally 30 minutes after distraction.
The FIRST response should be: