A 5-year-old girl is brought to the emergency department due to a 12-hour history of high … — USMLE Step 2 CK

A $5$ -year-old girl is brought to the emergency department due to a $12$ -hour history of high fever, severe frontal headache, and repeated vomiting. Over the past $2$ hours, she has become increasingly somnolent and difficult to rouse. Her temperature is $39.5^\circ\text{C}$ ( $103.1^\circ\text{F}$ ), blood pressure is $112/68\text{ mm Hg}$ , pulse is $135/\text{min}$ , and respirations are $26/\text{min}$ . Physical examination reveals marked nuchal rigidity and a positive Brudzinski sign. Neurologic examination demonstrates a Glasgow Coma Scale score of $10$ , sluggishly reactive pupils, and new-onset right-sided hemiparesis.

Arrange the following management steps in the most appropriate sequential order for this patient.

1Obtain peripheral blood cultures
2Administer empiric intravenous ceftriaxone, vancomycin, and dexamethasone
3Obtain a non-contrast computed tomography (CT) scan of the head
4Perform a lumbar puncture to obtain cerebrospinal fluid

Answer

The correct sequence is to first obtain blood cultures, immediately followed by the administration of empiric antibiotics and dexamethasone, then perform a head CT scan, and finally perform a lumbar puncture.

The standard of care for suspected bacterial meningitis requires prompt cerebrospinal fluid analysis via lumbar puncture, ideally before antibiotics are given. However, if a patient exhibits "red flag" signs such as altered mental status, new-onset seizures, focal neurologic deficits, or papilledema, a head CT is mandatory prior to lumbar puncture to rule out conditions that could cause cerebral herniation. Because the CT scan will delay the lumbar puncture, blood cultures must be drawn immediately, followed instantly by the administration of empiric antibiotics and dexamethasone. Once pharmacotherapy is initiated, the patient is sent for a CT scan. If the CT scan is reassuring, the lumbar puncture is then safely performed.

Step-by-Step Solution

Recognize the clinical presentation of suspected bacterial meningitis complicated by signs of increased intracranial pressure.

The patient has fever, nuchal rigidity, altered mental status (GCS 10), and a focal neurologic deficit (hemiparesis).

Identifying signs of increased intracranial pressure or a potential space-occupying lesion dictates the need for neuroimaging prior to invasive cerebrospinal fluid sampling.

Prioritize initial diagnostic cultures.

Obtain peripheral blood cultures as the first step.

Blood cultures provide a crucial opportunity to isolate the causative pathogen before antibiotics sterilize the blood, and they can be obtained rapidly without delaying life-saving therapy.

Initiate immediate life-saving pharmacotherapy.

Administer empiric intravenous ceftriaxone, vancomycin, and dexamethasone.

Because neuroimaging will delay the lumbar puncture, empiric therapy must be given immediately after blood cultures to prevent severe morbidity or mortality from untreated bacterial meningitis.

Perform risk-stratifying neuroimaging.

Obtain a non-contrast head CT scan.

The CT scan evaluates for significant mass effect, midline shift, or severe edema that would contraindicate a lumbar puncture due to the risk of brainstem herniation.

Perform definitive diagnostic testing.

Perform a lumbar puncture.

Once the CT scan confirms it is safe, cerebrospinal fluid should be obtained for analysis to guide targeted antimicrobial therapy, even if antibiotics have already been administered.

Key Concept

In patients with suspected bacterial meningitis who have indications for a head CT scan prior to lumbar puncture (e.g., altered mental status, focal neurologic deficits), blood cultures should be drawn and empiric antibiotics administered immediately, prior to neuroimaging.

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