Meningitis and encephalitis

^a Glucose: 1 mg/dL = 0.0555 mmol/L.

Antibiotic treatment should not be delayed for CT scan or until lumbar puncture results are available.
Empiric antibiotics are based on common organisms by age:
- 2–50 years old: N. meningitides, S. pneumoniae.
- >50 years old: S. pneumoniae, N. meningitides, L. monocytogenes.
A standard empiric regimen for meningitis in adults is
- Ceftriaxone 2 g IV every 12 hours and vancomycin 30 mg/kg loading and dosing every 12 hours for trough concentration of 15–20 micrograms/mL.
- Ampicillin 2 g IV every 4 hours for patients older than 50 years.
- Acyclovir 10 mg/kg IV every 8 hours for suspected HSV encephalitis.
Adjunctive dexamethasone is also recommended at 10 mg IV every 6 hours initiated prior to or concurrent with antibiotic therapy.

Patients with a history of shunt, recent neurosurgery, or penetrating trauma should receive anti-pseudomonal coverage as well.
Clinical findings and lumbar puncture results can be much more subtle in immunocompromised patients.

The most likely causes of decompensation are hemodynamic or respiratory impairment.
Patients should be evaluated for airway protection and those who are at risk of aspiration should be endotracheally intubated.
Patients who are hypotensive are likely septic and should be managed aggressively with fluids and pressors according to early goal-directed therapy protocols.
Nonconvulsive or convulsive status epilepticus can occur with encephalitis and should be managed with benzodiazepines as first-line agents.

Vasopressor of choice: Hypotensive patients are likely septic and should be managed with norepinephrine as a first-line agent.