Neurologic Critical Care
Intracranial physiology
Monro-Kellie doctrine: brain, blood, and CSF share a fixed volume; adding mass first displaces CSF and venous blood, then raises ICP steeply. CPP = MAP − ICP. A patient with ICP 22 and MAP 62 has CPP 40 - inadequate - and the correct response is to raise MAP, not merely to bolus osmotherapy.
Traumatic brain injury
Avoid hypoxia and hypotension (each independently worsens outcome). Target ICP <22 mmHg and CPP 60–70 mmHg. Hyperosmolar therapy (mannitol or hypertonic saline) for raised ICP; short-acting hyperventilation only as a bridge for impending herniation; no steroids. Seizure prophylaxis for 7 days after severe TBI but not longer.
Other entities
Aneurysmal subarachnoid hemorrhage: nimodipine, euvolemia, early aneurysm securing, watch for hydrocephalus and rebleeding. Intracerebral hemorrhage: smooth blood pressure control, reverse anticoagulation urgently. Ischemic stroke: thrombolysis within 4.5 hours in eligible patients, thrombectomy for large-vessel occlusion. Status epilepticus: benzodiazepine, then a second-line antiseizure drug, then intubation with anesthetic infusion for refractory cases; obtain EEG because nonconvulsive status is common.
Brain death
Exclude sedatives, neuromuscular blockade, hypothermia, and severe metabolic derangement; confirm apnea with an appropriate PaCO2 rise; document spinal reflexes do not preclude the diagnosis.
Traps
- Prophylactic hyperventilation in TBI.
- Steroids for TBI.
- Treating ICP while ignoring CPP.
- Assuming a sedated patient cannot be having seizures.
- Declaring brain death without a proper toxicology and temperature review.
Rule of thumb
Hypotension and hypoxia are the two most correctable causes of secondary brain injury; fix them before escalating sedation or osmotherapy.