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Difficulty: HardPhysiological Adaptation

A client is being treated in the emergency department for a severe asthma exacerbation. Upon admission, the client was highly anxious, tachypneic, and audibly wheezing. Initial arterial blood gas (ABG) results were: pH 7.52, PaCO2 28 mm Hg, HCO3- 24 mEq/L, and PaO2 68 mm Hg. Two hours later, the nurse notes that the client has become lethargic and the respiratory effort is shallow. A repeat ABG reveals: pH 7.36, PaCO2 44 mm Hg, HCO3- 24 mEq/L, and PaO2 58 mm Hg. Which of the following is the priority nursing action?

  1. Prepare the client for immediate endotracheal intubation and mechanical ventilation.Answer
  2. B
    Document the repeat ABG results as a positive therapeutic response to asthma treatments.
  3. C
    Administer a prescribed intravenous benzodiazepine to reduce anxiety and the work of breathing.
  4. D
    Instruct the client to practice pursed-lip breathing to maintain the current carbon dioxide level.

Answer

Prepare the client for immediate endotracheal intubation and mechanical ventilation.
In the early stages of an asthma exacerbation, clients hyperventilate in an attempt to increase oxygenation, resulting in a low PaCO2 (respiratory alkalosis). As the client becomes fatigued, they can no longer maintain this increased respiratory effort. The breathing becomes shallow, and CO2 begins to be retained. A PaCO2 that rises from a low level to a 'normal' level (35-45 mm Hg), accompanied by clinical signs of deterioration such as lethargy, is a classic warning sign of impending respiratory failure. The priority action is to prepare for immediate intubation and mechanical ventilation to secure the airway and ensure adequate gas exchange.

Step-by-Step Solution

1
Analyze the initial presentation and ABGs.
The client initially presented with hyperventilation (tachypnea), leading to respiratory alkalosis (pH 7.52, low PaCO2 28), which is a typical early physiological adaptation to hypoxemia in an asthma attack.
Establishing the baseline helps identify trends in the client's respiratory status.
2
Evaluate the current clinical signs and repeat ABGs.
The client is now lethargic with shallow breathing. The ABG shows a 'normal' pH (7.36) and PaCO2 (44), but worsening hypoxemia (PaO2 58).
Clinical assessment must always be correlated with laboratory values to determine the client's actual condition.
3
Synthesize the findings to determine the pathophysiological state.
The increase in PaCO2 from 28 to 44 mm Hg, combined with lethargy, means the client is no longer able to maintain the compensatory hyperventilation due to respiratory muscle fatigue.
A normalizing PaCO2 in a previously hyperventilating asthmatic is an ominous sign of impending respiratory failure.
4
Determine the highest priority intervention.
The client requires immediate airway protection and mechanical ventilation to prevent respiratory arrest.
Airway and breathing are the highest priorities in the ABCs of resuscitation.

Key Concept

Impending Respiratory Failure in Asthma
Estimated Time:1m 30s
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Topics

Physiological Adaptation

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