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Question

Difficulty: MediumInfectious Diseases

Emergency medical services bring an unresponsive 21-year-old university student to the emergency department. Her roommate reports she had been complaining of a severe headache, nausea, and photophobia for the past 24 hours. Vital signs show a temperature of 39.2°C (102.5°F), blood pressure of 90/60 mmHg, heart rate of 115/min, and respiratory rate of 22/min. Physical examination reveals marked nuchal rigidity and a diffuse non-blanching petechial rash on her lower extremities. Fundoscopic examination demonstrates bilateral papilledema.

Arrange the following diagnostic and therapeutic steps in the most appropriate chronological sequence for this patient's management.

  1. 1Obtain two sets of peripheral blood cultures
  2. 2Administer intravenous ceftriaxone, vancomycin, and dexamethasone
  3. 3Perform a non-contrast CT scan of the head
  4. 4Perform a lumbar puncture to obtain cerebrospinal fluid

Answer

The most appropriate chronological sequence is: 1) Obtain blood cultures, 2) Administer empiric antibiotics and dexamethasone, 3) Perform a CT scan of the head, 4) Perform a lumbar puncture.
This patient presents with a classic presentation of meningitis (fever, nuchal rigidity, altered mental status) and a petechial rash highly suspicious for meningococcemia. Due to the presence of papilledema and unresponsiveness, there is a high risk of brain herniation if a lumbar puncture is performed immediately. Therefore, a CT scan of the head is required prior to the procedure. However, initiating antimicrobial therapy is a medical emergency and must not be delayed while waiting for imaging. The correct sequence is to first draw blood cultures to maximize diagnostic yield, immediately administer empiric antibiotics (ceftriaxone, vancomycin) and dexamethasone, then proceed with the CT scan, and finally perform the lumbar puncture once mass effect has been ruled out.

Step-by-Step Solution

1
Draw peripheral blood cultures
Secures blood samples for microbiological testing.
Must be done first to guide targeted therapy, taking care not to significantly delay life-saving antibiotic administration.
2
Administer empiric antibiotics and dexamethasone
Provides immediate treatment for suspected bacterial meningitis.
Because the patient has papilledema and altered mental status, an immediate lumbar puncture is contraindicated. Antibiotics must never be delayed for neuroimaging in suspected bacterial meningitis.
3
Perform a non-contrast CT scan of the head
Evaluates for intracranial mass lesions, midline shift, or severe cerebral edema.
Required before a lumbar puncture in this patient due to signs of increased intracranial pressure (papilledema, altered mental status) to prevent brainstem herniation.
4
Perform a lumbar puncture
Obtains cerebrospinal fluid for cell count, chemistry, Gram stain, and culture.
Once the CT scan confirms the absence of mass effect, the lumbar puncture can be safely performed to definitively diagnose the central nervous system infection.

Key Concept

In patients with suspected bacterial meningitis who have indications for a CT scan before lumbar puncture (e.g., papilledema, altered mental status, focal neurologic deficits), blood cultures should be drawn immediately, followed by empiric antibiotics and corticosteroids, prior to sending the patient for the CT scan.
Estimated Time:1m 30s
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Topics

Infectious Diseases

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