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Difficulty: MediumPhysiological Adaptation

A client is admitted to the emergency department with an acute severe asthma exacerbation. Upon admission, the client is extremely restless, tachypneic with a respiratory rate of 34 breaths/min, and exhibiting loud, bilateral expiratory wheezes. The baseline arterial blood gas (ABG) on room air is obtained. Two hours later, after continuous bronchodilator therapy, the client becomes lethargic. The respiratory rate decreases to 14 breaths/min, and breath sounds are significantly diminished with minimal audible wheezing. A repeat ABG is drawn while the client is on a non-rebreather mask. The results are as follows:

ValueAdmission (Room Air)2 Hours Later (Non-rebreather)
pH7.507.28
PaCO228 mm Hg58 mm Hg
PaO268 mm Hg62 mm Hg
HCO3-23 mEq/L24 mEq/L

Based on these findings, which action should the nurse take first?

  1. A
    Document the decreased wheezing as a positive response to the bronchodilators.
  2. B
    Switch the client's oxygen delivery system to a venturi mask to provide a precise FiO2.
  3. Prepare the client for immediate endotracheal intubation.Answer
  4. D
    Administer a prescribed PRN dose of intravenous methylprednisolone.

Answer

Prepare the client for immediate endotracheal intubation.
In an acute asthma exacerbation, clients initially hyperventilate, leading to respiratory alkalosis. If the client begins to fatigue from the extreme work of breathing, ventilation decreases, causing carbon dioxide retention (respiratory acidosis). The combination of respiratory acidosis, lethargy, and diminished breath sounds (a 'silent chest') is a critical medical emergency indicating impending respiratory failure. The immediate priority is to secure the airway and initiate mechanical ventilation.

Step-by-Step Solution

1
Analyze the baseline assessment and initial ABG.
The client was hyperventilating, causing uncompensated respiratory alkalosis (pH 7.50, PaCO2 28 mm Hg).
To establish the client's initial baseline and understand the early compensatory mechanism in an asthma attack.
2
Analyze the repeat assessment and second ABG.
The client has developed uncompensated respiratory acidosis (pH 7.28, PaCO2 58 mm Hg) and is displaying lethargy with diminished breath sounds.
To identify any clinical deterioration or significant changes in the client's respiratory status.
3
Correlate clinical findings with asthma pathophysiology.
The shift from alkalosis to acidosis, combined with lethargy and a 'silent chest' (diminished wheezing), indicates severe respiratory muscle fatigue and inability to ventilate.
To determine the true severity and meaning behind the sudden decrease in wheezing and rising CO2.
4
Determine the highest priority nursing action.
The nurse must prepare for immediate endotracheal intubation.
Impending respiratory failure requires immediate advanced airway management to prevent cardiac and respiratory arrest.

Key Concept

Identifying impending respiratory failure in an acute asthma exacerbation by recognizing the shift from respiratory alkalosis to respiratory acidosis and the clinical sign of a 'silent chest.'
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Topics

Physiological Adaptation

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