Neurologic and Neurosurgical Critical Care
Intracranial dynamics
The Monro-Kellie doctrine states that brain, blood, and cerebrospinal fluid share a fixed volume, so adding any component raises intracranial pressure (ICP). Cerebral perfusion pressure equals mean arterial pressure minus ICP; typical targets are above 40 mmHg in infants and above 50 mmHg in older children. Autoregulation may be impaired after trauma, making pressure support critical.
Assessment and management
Use the Glasgow Coma Scale, pupillary examination, and serial neurologic checks. Cushing triad of hypertension, bradycardia, and irregular respiration signals herniation. Elevate the head, keep the neck midline, maintain normothermia, avoid hypotension and hypoxemia, and use hyperosmolar therapy (3% saline 3-5 mL/kg or mannitol 0.25-1 g/kg) for raised ICP. Brief hyperventilation is a bridge to definitive treatment, not a sustained strategy. Treat seizures promptly; status epilepticus follows benzodiazepines with levetiracetam or fosphenytoin, then a midazolam infusion. Avoid hypotonic fluids and steroids in traumatic brain injury.
Traps
A single normal ICP does not exclude herniation. Hyperthermia worsens outcomes. Prophylactic anticonvulsants may be used early after severe traumatic brain injury but are not continued indefinitely without seizures. Do not correct a high PaCO2 aggressively in a child with normal ICP.
Worked rule
A child has MAP 62 mmHg and ICP 22 mmHg. CPP is 40 mmHg, below the target of about 50 mmHg, so the priority is raising MAP and lowering ICP, not giving a fluid bolus of hypotonic solution.