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Question

Difficulty: HardInfectious Diseases

A 62-year-old female presents to the emergency room accompanied by her daughter, who reports that her mother has been increasingly confused and feverish over the preceding 24 hours. Her past medical history is notable for a deceased-donor renal transplant performed three years ago, maintained on a regimen of tacrolimus and mycophenolate mofetil. Vital signs show a temperature of 39.4°C (102.9°F), blood pressure of 110/65 mm Hg, pulse of 112/min, and respirations of 20/min. Physical examination reveals marked nuchal rigidity and a positive Kernig sign. The patient is somnolent but arousable to verbal stimuli. There are no focal motor deficits, but fundoscopic examination is deferred due to poor patient cooperation. The clinical team suspects acute bacterial meningitis and prepares to initiate the management protocol. Arrange the following critical next steps in the most appropriate chronological sequence.

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

Answer

The correct sequence is: Obtain blood cultures, administer empiric antibiotics and dexamethasone, perform a CT scan of the head, and finally perform a lumbar puncture.
The correct sequence for managing suspected bacterial meningitis in a patient with indications for neuroimaging prior to lumbar puncture begins with obtaining blood cultures. Indications for a CT scan before lumbar puncture include an immunocompromised state, history of central nervous system disease, new-onset seizure, papilledema, focal neurologic deficit, or altered mental status. Because the CT scan will delay the lumbar puncture, immediate administration of empiric antibiotics (including ampicillin for Listeria coverage in an immunocompromised host) and adjunctive dexamethasone follows. A noncontrast CT of the head is then performed to rule out mass effect, and if safe, the lumbar puncture is performed last.

Step-by-Step Solution

1
Identify indications for neuroimaging prior to lumbar puncture.
The patient has an immunocompromised state (renal transplant) and altered mental status (somnolence), both of which mandate a CT scan of the head before performing a lumbar puncture.
Performing a lumbar puncture in the presence of a space-occupying lesion can lead to fatal cerebral herniation.
2
Determine the impact of the required CT scan on treatment timing.
Because the CT scan will delay the lumbar puncture, empiric therapy must be given beforehand.
Delaying antimicrobial therapy in bacterial meningitis significantly increases mortality and neurologic morbidity.
3
Sequence the interventions appropriately based on diagnostic yield and therapeutic urgency.
Blood cultures are drawn first, immediately followed by empiric antibiotics and dexamethasone, then the CT scan, and finally the lumbar puncture.
Blood cultures should be drawn before antibiotics sterilize the blood, but antibiotics must be given before the patient leaves for the CT scanner.

Key Concept

Management sequence for suspected bacterial meningitis with high-risk features requiring neuroimaging prior to lumbar puncture.
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Topics

Infectious Diseases

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