General Critical Care Medicine for the Neuro Patient
The organizing framework
General critical care in a neuro exam tests whether you can manage oxygenation, hemodynamics, electrolytes, and infection without causing secondary brain injury. The central principle: the brain is an organ that tolerates hypoxia, hypotension, hypo/hyperglycemia, and fever poorly. Every general ICU decision should be filtered through its effect on cerebral perfusion and metabolism.
Must-know concepts
- Ventilation: lung-protective strategies (low tidal volume) apply, but permissive hypercapnia is generally avoided when ICP is elevated because CO2 dilates cerebral vessels and raises ICP.
- Hemodynamics: fluid resuscitation and vasopressors to maintain MAP; distinguish hypovolemic from distributive shock.
- Sodium and osmolality: both hyponatremia (cerebral edema, seizures) and overly rapid correction (osmotic demyelination) are tested; SIADH vs cerebral salt wasting is a classic distinction.
- Glucose control: avoid both hypoglycemia and marked hyperglycemia.
- Fever: treat aggressively; fever worsens outcome after brain injury.
- Sedation and analgesia can confound the neurologic exam; know which agents preserve reactivity.
Traps
A frequent trap is choosing a therapy that is correct for general ICU patients but harmful here-for example, aggressive hyperventilation, or rapid correction of chronic hyponatremia. Another is missing that a "stable" patient is actually hypotensive relative to their brain's needs.
Worked example
A comatose patient has serum sodium 118 mmol/L. The safe correction rate is generally ≤8–10 mmol/L in 24 hours to reduce osmotic demyelination risk. Rule of thumb: slow and steady for sodium; fast and aggressive for herniation-the two urgency profiles are opposite.