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Difficulty: MediumPediatric Respiratory Disorders

An 11-year-old boy is brought to the pediatric emergency department due to severe, worsening shortness of breath over the past 24 hours. He has a known history of moderate persistent asthma and has been using his albuterol inhaler every 2 hours at home without relief. On arrival, the patient appears lethargic and diaphoretic. He is only able to speak in single syllables. His temperature is 37.2∘C37.2^\circ\text{C} (99.0∘F99.0^\circ\text{F}), pulse is 155/min155/\text{min}, respirations are 14/min14/\text{min}, and blood pressure is 112/68 mm Hg112/68\text{ mm Hg}. Pulse oximetry is 87%87\% on room air. Lung auscultation reveals a "silent chest" with profoundly diminished air entry bilaterally and minimal wheezing.

An arterial blood gas analysis on room air shows:
ParameterValueReference Range
pH7.247.247.35−7.457.35 - 7.45
PaO₂58 mmHg58\text{ mmHg}75−105 mmHg75 - 105\text{ mmHg}
PaCO₂56 mmHg56\text{ mmHg}35−45 mmHg35 - 45\text{ mmHg}

Which of the following is the most appropriate next step in management?

  1. A
    Administration of intravenous ceftriaxone and azithromycin
  2. B
    Administration of intravenous sodium bicarbonate
  3. C
    Administration of nebulized hypertonic saline
  4. Endotracheal intubationAnswer
  5. E
    Obtaining a computed tomography scan of the chest

Answer

Endotracheal intubation
The correct answer is endotracheal intubation. This patient is in status asthmaticus and exhibiting textbook signs of impending respiratory failure. During an acute asthma exacerbation, increased work of breathing typically leads to hyperventilation and a respiratory alkalosis (low PaCO2). However, as the patient tires and respiratory muscles fatigue, ventilation decreases, leading to a "normalization" or elevation of the PaCO2. In this patient, a PaCO2 of 56 mmHg combined with lethargy, bradypnea (14/min in a severely dyspneic 11-year-old), and a "silent chest" (airflow is too poor to generate wheezing) confirms impending respiratory arrest. The most appropriate immediate intervention is to secure the airway with endotracheal intubation and initiate mechanical ventilation.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and vital signs.
The patient demonstrates altered mental status (lethargy), an inappropriately low respiratory rate for the degree of distress (14/min), hypoxia, and a 'silent chest'.
To rapidly assess the severity of the asthma exacerbation and identify signs of clinical exhaustion.
2
Evaluate the arterial blood gas (ABG) findings in the context of the physical exam.
The ABG reveals primary respiratory acidosis (pH 7.24) with significant hypercapnia (PaCO2 56 mmHg).
To determine the adequacy of ventilation. In a typical asthma attack, hyperventilation causes a low PaCO2; a normal or high PaCO2 indicates severe respiratory muscle fatigue.
3
Determine the next best step in management.
The combination of hypercapnia and clinical exhaustion confirms impending respiratory failure, necessitating immediate definitive airway management.
To secure the airway, provide mechanical ventilation, and prevent imminent respiratory arrest.

Key Concept

Recognition of impending respiratory failure in status asthmaticus, indicated by altered mental status, a 'silent chest', and a normal or elevated PaCO2.
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Topics

Pediatric Respiratory Disorders

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