In mid-January, a distressed father arrives at the emergency department with his 15-month-… — USMLE Step 2 CK

In mid-January, a distressed father arrives at the emergency department with his $15$ -month-old toddler. The child has been experiencing rapidly worsening respiratory distress over the past $12$ hours. The father reports that the illness began $4$ days ago with a runny nose, mild cough, and decreased appetite. The child's medical history is significant for atopic dermatitis, and his $6$ -year-old sister recently missed school due to a severe asthma exacerbation.

Temperature is $38.1^\circ\text{C}$ ( $100.6^\circ\text{F}$ ), pulse is $172$ /min, and respirations are $68$ /min. Pulse oximetry shows an oxygen saturation of $87\%$ on room air. The child appears lethargic but becomes irritable when handled. Physical examination reveals marked nasal flaring, grunting, and deep subcostal retractions. Auscultation of the chest demonstrates a prolonged expiratory phase with diffuse polyphonic wheezes, as well as fine inspiratory crackles at both lung bases. Cardiac examination reveals a regular tachycardia without murmurs. The liver edge is palpable $3$ cm below the right costal margin.

Capillary blood gas analysis on room air reveals the following:

Parameter	Value	Reference Range
pH	$7.30$	$7.35 - 7.45$
pCO $_2$	$56$ mmHg	$35 - 45$ mmHg
pO $_2$	$50$ mmHg	$80 - 100$ mmHg
HCO $_3^-$	$26$ mEq/L	$22 - 28$ mEq/L

Which of the following is the most appropriate initial management for this patient?

A
Administration of systemic corticosteroids and inhaled beta-2 agonists
Provision of supplemental oxygen therapy and upper airway suctioningAnswer
C
Intravenous administration of ceftriaxone and azithromycin
D
Administration of intravenous furosemide and implementation of fluid restriction
E
Intravenous infusion of sodium bicarbonate to correct the acid-base derangement

Answer

The most appropriate initial management is the provision of supplemental oxygen therapy and upper airway suctioning.

The correct intervention is the provision of supplemental oxygen therapy and upper airway suctioning. This patient is presenting with severe viral bronchiolitis, evidenced by his age (15 months), the winter season, a 4-day viral prodrome (rhinorrhea), and the hallmark physical exam finding of wheezing combined with fine inspiratory crackles. The crackles represent alveolar and small-airway fluid and cellular debris, which distinguishes bronchiolitis from asthma. Because bronchiolitis is a self-limiting viral illness, the standard of care is entirely supportive. Given his significant hypoxia (SpO2 87%) and impending respiratory fatigue (acute respiratory acidosis on CBG with a pCO2 of 56 mmHg), supplemental oxygen is immediately indicated. Upper airway suctioning is also critical as infants are obligate nasal breathers, and clearing secretions can significantly decrease the work of breathing.

Step-by-Step Solution

Analyze the patient's demographics, history, and timing.

The patient is a 15-month-old presenting in mid-winter with a 4-day viral prodrome (rhinorrhea) followed by respiratory distress.

Establishing the classic epidemiological and historical pattern for viral bronchiolitis (most commonly Respiratory Syncytial Virus).

Differentiate the physical exam findings from alternative diagnoses.

The presence of diffuse polyphonic wheezes AND fine inspiratory crackles is highly specific for bronchiolitis (inflammation and sloughing of bronchiolar epithelium). Asthma typically presents with wheezing without crackles.

To deliberately override the cognitive bias created by the patient's history of eczema and family history of asthma, ensuring accurate diagnosis.

Interpret the palpable liver edge in the context of respiratory distress.

The liver is palpable 3 cm below the costal margin due to downward displacement by hyperinflated lungs (flattened diaphragms), not due to true hepatomegaly or right heart failure.

To rule out cardiac etiologies that would require completely different management (e.g., diuretics).

Evaluate the capillary blood gas.

pH is 7.30 and pCO2 is 56 mmHg, indicating an acute respiratory acidosis secondary to air trapping and respiratory muscle fatigue.

To assess the severity of the respiratory failure and confirm that the primary issue is ventilation/oxygenation, not a primary metabolic derangement.

Determine the standard of care intervention for the confirmed diagnosis.

Supportive care with supplemental oxygen (due to SpO2 < 90%) and nasal suctioning (to relieve upper airway obstruction from secretions) is selected.

Pharmacotherapy such as bronchodilators, systemic corticosteroids, and antibiotics lack efficacy in viral bronchiolitis and are not recommended by clinical guidelines.

Key Concept

The diagnosis of viral bronchiolitis is clinical, characterized by a viral prodrome followed by respiratory distress, wheezing, and crackles in children under 2 years. Management is strictly supportive (oxygen and hydration), avoiding unproven therapies like albuterol and corticosteroids, even in patients with atopic risk factors.

Estimated Time:1m 30s

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic