Neuroanesthesia and Neurocritical Care
Core concepts
Understand cerebral blood flow autoregulation, the Monro-Kellie doctrine, and the determinants of intracranial pressure (ICP). Know how PaCO2, PaO2, mean arterial pressure, and cerebral metabolic rate affect CBF. Master the principles of neuroprotection: normothermia, normoglycemia, normocapnia, and avoidance of hypotension. Understand the management of raised ICP (head elevation, sedation, osmotherapy, controlled hyperventilation as a bridge). Know the anesthetic implications for craniotomy, awake craniotomy, and spine surgery, and the recognition and management of postoperative complications such as hematoma, seizures, and hyponatremia. Understand the Glasgow Coma Scale and brain-death criteria at a conceptual level.
Traps in questions
- Using hyperventilation as a routine rather than a short-term bridge; prolonged hypocapnia can cause ischemia.
- Forgetting that autoregulation is impaired in injured brain, so blood pressure changes directly affect CBF.
- Confusing the Monro-Kellie doctrine (fixed skull volume) with the ability to compensate via CSF and blood displacement.
- Missing that hyponatremia after neurosurgery may be SIADH or cerebral salt wasting, which have different volume status.
- Assuming a normal CT excludes raised ICP.
Worked example / rule of thumb
A patient with a traumatic brain injury and rising ICP: first ensure oxygenation and normocapnia, then head elevation, sedation, and osmotic therapy. Rule of thumb: every 1 mmHg rise in PaCO2 increases CBF by roughly 4%; use hyperventilation briefly and only for impending herniation.
Exam framing
Questions often test which intervention is first in raised ICP. Airway and oxygenation come before osmotic therapy, and hyperventilation is a rescue, not a maintenance strategy.