A previously well 1-year-old infant has had a runny nose and has been sneezing and coughing for 2 days. Two other members of the family had similar symptoms. Four hours ago, his cough became much worse. On physical examination in the ED, he is in moderate respiratory distress with tachypnea and nasal flaring. Upon auscultation, he has easily audible wheezing with scattered crackles bilaterally. His arterial blood gas on room air revealed a pH of 7.46, a PaCO2 of 34 mm Hg, and a PaO2 of 75 mm Hg. His chest radiographs are shown. Which of the following is the appropriate next course of action?

**Core Concept**
The infant's symptoms and physical examination findings are consistent with a viral lower respiratory tract infection, specifically bronchiolitis. This condition is characterized by inflammation and congestion of the small airways, leading to respiratory distress and wheezing.

**Why the Correct Answer is Right**
The infant's arterial blood gas (ABG) results show a mild alkalosis (pH 7.46) and a normal PaCO2 level, indicating that the respiratory alkalosis is likely due to hyperventilation in response to the respiratory distress. The low PaO2 level (75 mm Hg) suggests hypoxemia, which is consistent with the infant's respiratory symptoms. The presence of scattered crackles on auscultation and the chest radiograph findings are also consistent with bronchiolitis.

**Why Each Wrong Option is Incorrect**
**Option A:** Administration of oxygen therapy would be appropriate if the infant's PaO2 level was significantly lower, indicating severe hypoxemia. However, with a PaO2 of 75 mm Hg, oxygen therapy is not immediately necessary.
**Option B:** Nasal suctioning may be helpful in relieving nasal congestion, but it would not address the underlying cause of the infant's respiratory distress. It is also not the most appropriate next course of action given the infant's moderate respiratory distress and hypoxemia.
**Option C:** Administration of epinephrine (adrenaline) is not indicated in this case, as the infant's symptoms are consistent with a viral infection rather than anaphylaxis or asthma.
**Option D:** Administration of a bronchodilator, such as albuterol, may be helpful in relieving bronchospasm, but it would not address the underlying cause of the infant's respiratory distress, which is likely due to viral infection and inflammation.

**Clinical Pearl / High-Yield Fact**
In infants with bronchiolitis, the respiratory alkalosis is often due to hyperventilation in response to the respiratory distress, rather than a primary metabolic alkalosis. This is an important distinction to make when interpreting ABG results in pediatric patients.

**Correct Answer:** C. Administration of epinephrine (adrenaline)

✓ Correct Answer: A. Monitoring oxygenation and fluid status