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Difficulty: MediumPhysiological Adaptation

A client is receiving treatment in the emergency department for a severe asthma exacerbation. The client's initial presentation included marked restlessness, a respiratory rate of 34 breaths/min, and an arterial blood gas (ABG) revealing a pH of 7.49 and a PaCO₂ of 27 mm Hg. After two hours of therapy, the nurse observes that the client has become profoundly lethargic and the respiratory rate has decreased to 14 breaths/min. A follow-up ABG shows a pH of 7.28 and a PaCO₂ of 62 mm Hg. Which of the following is the priority nursing action?

  1. Prepare the team and equipment for immediate endotracheal intubation and mechanical ventilation.Answer
  2. B
    Document the decrease in respiratory rate as a successful physiological response to the asthma therapy.
  3. C
    Initiate a rapid intravenous fluid bolus to address early clinical manifestations of shock.
  4. D
    Perform a thorough auscultation of all lung fields to evaluate the efficacy of the administered bronchodilators.

Answer

The priority action is to prepare the team and equipment for immediate endotracheal intubation and mechanical ventilation.
During a severe asthma exacerbation, clients initially hyperventilate, leading to respiratory alkalosis. If the asthma is not resolved, respiratory muscles become exhausted. This fatigue causes the respiratory rate to drop, leading to CO₂ retention (respiratory acidosis) and subsequent altered mental status (lethargy). This physiological collapse indicates impending respiratory failure, making preparation for endotracheal intubation the immediate life-saving priority.

Step-by-Step Solution

1
Analyze the initial clinical presentation.
The client was initially hyperventilating (RR 34) with respiratory alkalosis (pH 7.49, low PaCO₂).
This is a typical early physiological adaptation to hypoxemia during an asthma attack.
2
Evaluate the clinical changes and the follow-up ABG.
The client is now lethargic with a 'normal' RR (14), but the ABG shows uncompensated respiratory acidosis (pH 7.28, high PaCO₂).
A falling respiratory rate and rising PaCO₂ in a severe asthma exacerbation signal respiratory muscle fatigue and loss of compensatory mechanisms.
3
Determine the priority nursing intervention based on ABCs (Airway, Breathing, Circulation).
The client is experiencing impending respiratory failure.
Immediate mechanical ventilation is required to restore gas exchange and prevent cardiac arrest.

Key Concept

In severe asthma, a transition from respiratory alkalosis to respiratory acidosis accompanied by lethargy and a normalizing respiratory rate indicates impending respiratory failure requiring immediate intubation.
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Physiological Adaptation

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