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Difficulty: MediumInfectious Diseases

A 58-year-old woman is brought to the emergency department by her husband due to a 24-hour history of severe headache, confusion, and high fever. Her temperature is 39.2°C (102.6°F), blood pressure is 110/70 mm Hg, pulse is 115/min, and respirations are 18/min. Physical examination reveals marked nuchal rigidity. Funduscopic examination shows bilateral optic disc swelling (papilledema). She is somnolent but localizes to painful stimuli. There are no focal motor deficits. The physician suspects acute bacterial meningitis. Arrange the following interventions in the most appropriate chronological order of execution.

  1. 1Obtain blood cultures
  2. 2Administer empiric intravenous dexamethasone and antibiotics
  3. 3Perform a non-contrast CT scan of the head
  4. 4Perform a lumbar puncture

Answer

The correct sequence of management is: Obtain blood cultures, followed by administration of empiric intravenous dexamethasone and antibiotics, then perform a non-contrast CT scan of the head, and finally perform a lumbar puncture.
In adult patients with suspected bacterial meningitis who exhibit high-risk features (altered mental status, papilledema, focal neurologic deficits, new-onset seizures, or an immunocompromised state), a head CT is mandatory before a lumbar puncture. However, because obtaining the CT scan will delay the lumbar puncture, empiric antibiotic therapy and adjunctive dexamethasone must be initiated immediately after blood cultures are drawn. Therefore, the exact order is: Blood cultures -> Empiric antibiotics + Dexamethasone -> Head CT -> Lumbar Puncture.

Step-by-Step Solution

1
Identify indications for a head CT scan prior to lumbar puncture.
The patient has papilledema and altered mental status, which are high-risk features dictating the need for a head CT before proceeding with a lumbar puncture.
Performing a lumbar puncture in the presence of focal intracranial lesions or significantly elevated intracranial pressure can precipitate life-threatening brain herniation.
2
Determine the sequence of diagnostics and therapeutics in cases where a CT scan delays the lumbar puncture.
Blood cultures must be drawn, immediately followed by empiric antibiotics and dexamethasone, before sending the patient to the CT scanner.
Bacterial meningitis is a medical emergency. If a lumbar puncture is delayed by the need for neuroimaging, antimicrobial therapy must not be delayed, as early administration significantly reduces mortality and neurologic morbidity.
3
Sequence the diagnostic imaging and invasive procedure.
The CT scan is performed, followed by the lumbar puncture if the CT is negative for mass effect.
The CT ensures safety. Even though antibiotics have already been administered, the lumbar puncture is still necessary to analyze the cerebrospinal fluid (e.g., cell counts, protein, glucose, and bacterial antigens or PCR) to confirm the diagnosis and streamline therapy.

Key Concept

Management sequence for suspected bacterial meningitis with high-risk features
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Topics

Infectious Diseases

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