A 3-week-old male infant is evaluated in the emergency department for a 12-hour history of… — USMLE Step 2 CK

A $3$ -week-old male infant is evaluated in the emergency department for a $12$ -hour history of decreased feeding and increased somnolence. The parents report that he has been difficult to rouse for his usual feedings. He was born at term via an uncomplicated vaginal delivery to a mother who received standard prenatal care. Vital signs reveal a rectal temperature of $38.6^\circ\text{C}$ ( $101.5^\circ\text{F}$ ), heart rate of $168/\text{min}$ , respiratory rate of $54/\text{min}$ , and blood pressure of $70/45\text{ mmHg}$ . Physical examination shows a lethargic infant who awakens only briefly to stimulation. The anterior fontanelle is soft and flat. Cardiopulmonary examination is unremarkable, with no wheezing or retractions. Skin examination reveals scattered $1$ to $2\text{ mm}$ yellow-white pustules on a splotchy erythematous base distributed over the anterior chest and back. Which of the following is the most appropriate next step in management?

Perform a full sepsis evaluation and initiate intravenous ampicillin and gentamicinAnswer
B
Initiate intravenous vancomycin and cefepime pending blood culture results
C
Admit for observation and initiate intravenous acyclovir monotherapy
D
Administer nebulized albuterol and monitor oxygen saturation
E
Provide reassurance, administer the scheduled rotavirus vaccine, and discharge home

Answer

The most appropriate next step is to perform a full sepsis evaluation and initiate intravenous ampicillin and gentamicin.

Any infant less than

28\text{ days}

old with a fever (rectal temperature

\ge 38.0^\circ\text{C}

100.4^\circ\text{F}

) requires a full sepsis evaluation, which includes blood, urine, and cerebrospinal fluid cultures. Because clinical signs of infection in neonates are non-specific and they can deteriorate rapidly, empiric intravenous antibiotics must be initiated immediately after cultures are obtained. The standard empiric regimen is ampicillin (to cover Listeria monocytogenes and group B Streptococcus) and an aminoglycoside such as gentamicin (to cover gram-negative organisms like Escherichia coli). The infant's cutaneous findings represent erythema toxicum neonatorum, a benign and self-limiting condition that should not alter or delay the mandatory sepsis pathway.

Step-by-Step Solution

Identify the critical clinical presentation.

A 3-week-old neonate presents with a documented fever of

38.6^\circ\text{C}

and clear signs of lethargy.

Neonates have immature cell-mediated immunity and are at an exceptionally high risk for invasive bacterial infections, making fever a medical emergency.

Evaluate the dermatologic findings.

The scattered yellow-white pustules on an erythematous base correctly identify erythema toxicum neonatorum.

This is a benign, self-limiting newborn rash that requires no specific intervention and should not distract from the primary sepsis workup.

Determine the required diagnostic and therapeutic interventions.

A full sepsis workup (blood, urine, and cerebrospinal fluid cultures) must be performed, followed immediately by empiric ampicillin and gentamicin.

This antibiotic regimen specifically targets the most common neonatal pathogens: group B Streptococcus, Escherichia coli, and Listeria monocytogenes.

Key Concept

Any neonate under 28 days of age presenting with a fever requires an immediate full sepsis evaluation and empiric treatment with intravenous ampicillin and an aminoglycoside (or third-generation cephalosporin), regardless of other benign physical exam findings.

Estimated Time:1m 15s

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