During a busy winter shift at the pediatric emergency department, a 6-week-old female infa… — USMLE Step 2 CK

During a busy winter shift at the pediatric emergency department, a $6$ -week-old female infant is triaged for severe respiratory distress. The parents describe a prodrome of clear rhinorrhea and a mild cough that began $4$ days prior. However, since this morning, she has been refusing to feed and appears to be struggling for each breath. She was born via spontaneous vaginal delivery at $39$ weeks gestation with an uncomplicated postnatal course.

Vital signs are as follows:
- Temperature: $37.6^\circ\text{C}$ ( $99.7^\circ\text{F}$ )
- Heart rate: $172$ /min
- Respiratory rate: $70$ /min
- Blood pressure: $85/50$ mm Hg
- Oxygen saturation: $85\%$ on room air

Physical examination reveals an ill-appearing infant with marked head bobbing, severe intercostal and subcostal retractions, and prominent nasal flaring. Lung auscultation demonstrates bilateral diffuse fine crackles and high-pitched expiratory wheezing. Capillary refill time is $3$ seconds.

Which of the following therapies are currently indicated for this patient? (Select all that apply)

Initiation of supplemental oxygen via high-flow nasal cannulaAnswer
Administration of intravenous isotonic crystalloid fluidsAnswer
C
Inhalation of nebulized albuterol
D
Administration of intravenous methylprednisolone
E
Empiric therapy with intravenous ceftriaxone

Answer

The indicated therapies for this patient are the initiation of supplemental oxygen via high-flow nasal cannula and the administration of intravenous isotonic crystalloid fluids.

The correct management steps are the initiation of supplemental oxygen via high-flow nasal cannula and the administration of intravenous isotonic crystalloid fluids. This infant presents with classic severe viral bronchiolitis, characterized by a viral upper respiratory prodrome progressing to lower respiratory tract signs (wheezing, crackles) and severe respiratory distress. The cornerstone of bronchiolitis management is supportive care. With an oxygen saturation of

85\%

, this patient requires immediate supplemental oxygen; high-flow nasal cannula (HFNC) is often preferred as it provides both heated, humidified oxygen and continuous distending pressure to stent open inflamed small airways. Furthermore, the patient's severe tachypnea (respiratory rate

70

/min) and increased work of breathing make oral feeding unsafe due to a high risk of aspiration. Therefore, providing hydration via intravenous isotonic fluids is an essential, life-sustaining intervention.

Step-by-Step Solution

Diagnose the underlying condition based on patient age and clinical presentation.

The patient is a 6-week-old infant with a viral prodrome followed by severe respiratory distress and wheezing, leading to a clinical diagnosis of severe viral bronchiolitis (most commonly due to Respiratory Syncytial Virus).

Accurately identifying bronchiolitis is critical to differentiate it from pediatric asthma, as the pathophysiologies and evidence-based treatments differ significantly.

Assess the severity of the respiratory distress to guide supportive care.

The patient has severe hypoxemia (SpO2 85%) and signs of impending respiratory failure (head bobbing, severe retractions, tachypnea of 70/min).

The degree of severity determines the level of supportive care needed, specifically the urgency of oxygenation and fluid management.

Select appropriate supportive therapies.

High-flow nasal cannula (HFNC) is selected to provide oxygen and distending pressure. Intravenous fluids are selected because enteral feeding is contraindicated at a respiratory rate of 70/min.

Supportive care targeting oxygenation and hydration is the proven mainstay of treatment for viral bronchiolitis.

Rule out inappropriate pharmacological interventions commonly used for other respiratory conditions.

Bronchodilators, systemic corticosteroids, and broad-spectrum antibiotics are excluded from the management plan.

These medications do not improve outcomes in viral bronchiolitis and expose the infant to unnecessary adverse effects and antimicrobial resistance.

Key Concept

The management of severe viral bronchiolitis in infants is entirely supportive, prioritizing adequate oxygenation (e.g., HFNC) and safe hydration (IV or enteral fluids if RR permits), while strictly avoiding ineffective pharmacological treatments like bronchodilators, systemic corticosteroids, and antibiotics.

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