A 9-year-old girl is transported to the emergency department by ambulance due to severe re… — USMLE Step 2 CK

A 9-year-old girl is transported to the emergency department by ambulance due to severe respiratory distress. According to her parents, she has a history of moderate persistent asthma but exhausted her supply of inhaled corticosteroids two weeks ago. Yesterday, she developed a persistent cough and shortness of breath that did not respond to repeated doses of a short-acting bronchodilator. On evaluation, the patient appears exhausted, lethargic, and is leaning forward in a tripod position. Her temperature is $37.1^\circ \text{C}$ ( $98.8^\circ \text{F}$ ), blood pressure is $112/68 \text{ mm Hg}$ , heart rate is $152/\text{min}$ , and respiratory rate is $44/\text{min}$ . Pulse oximetry shows an oxygen saturation of $87\%$ on room air. Physical examination is notable for severe suprasternal and intercostal retractions. Auscultation reveals a "silent chest" with markedly diminished air entry bilaterally and no audible wheezing. An arterial blood gas on room air reveals a pH of $7.36$ , a $\text{PaCO}_2$ of $44 \text{ mm Hg}$ , and a $\text{PaO}_2$ of $58 \text{ mm Hg}$ . Which of the following is the most appropriate next step in management?

Preparation for immediate endotracheal intubationAnswer
B
Administration of intravenous ceftriaxone and azithromycin
C
Administration of nebulized hypertonic saline
D
Administration of intravenous sodium bicarbonate
E
Observation and continuous nebulized albuterol therapy

Answer

Preparation for immediate endotracheal intubation

The correct answer is preparation for immediate endotracheal intubation. This patient is in status asthmaticus with clear signs of impending respiratory failure. Clinically, she is lethargic (indicating hypercapnia/hypoxia affecting the brain) and has a "silent chest" (indicating bronchospasm so severe that air cannot move enough to generate wheezing). Physiologically, a patient breathing at

44/\text{min}

should have a low

\text{PaCO}_2

(respiratory alkalosis). The fact that her

\text{PaCO}_2

has normalized to

44 \text{ mm Hg}

means her respiratory muscles are fatiguing and she is losing the ability to ventilate. Immediate intubation and mechanical ventilation are life-saving and take precedence over other medical therapies.

Step-by-Step Solution

Evaluate the patient's clinical presentation.

The patient demonstrates lethargy, an inability to maintain respiratory effort (tripod positioning), and a "silent chest" (indicating severe bronchoconstriction with minimal air movement).

Clinical signs are the primary indicators of a patient's respiratory status and dictate the urgency of intervention.

Interpret the arterial blood gas (ABG) in the context of the patient's vital signs.

Despite a severe tachypnea of

44/\text{min}

, the

\text{PaCO}_2

44 \text{ mm Hg}

(normal is

35-45 \text{ mm Hg}

During an early or moderate asthma exacerbation, hyperventilation leads to a low

\text{PaCO}_2

(respiratory alkalosis). A "normal" or elevated

\text{PaCO}_2

in a highly tachypneic asthmatic indicates respiratory muscle fatigue and impending respiratory arrest.

Determine the next best step in management.

The patient requires immediate advanced airway management (endotracheal intubation and mechanical ventilation).

Medical therapies (e.g., continuous bronchodilators, magnesium sulfate) take time to work and do not protect the airway in a patient who is lethargic and actively failing to ventilate.

Key Concept

In a patient with a severe asthma exacerbation, altered mental status, a 'silent chest', and a normal or elevated PaCO2 indicate respiratory muscle fatigue and impending respiratory failure, necessitating immediate endotracheal intubation.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic