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Difficulty: EasyPhysiological Adaptation

A nurse is caring for a client who is exhibiting severe respiratory depression with a respiratory rate of 8 breaths per minute following an opioid overdose. Which of the following arterial blood gas (ABG) results should the nurse most likely expect to find?

  1. A
    pH 7.52, PaCO2 28 mm Hg, HCO3- 24 mEq/L
  2. B
    pH 7.31, PaCO2 40 mm Hg, HCO3- 16 mEq/L
  3. pH 7.28, PaCO2 55 mm Hg, HCO3- 24 mEq/LAnswer
  4. D
    pH 7.49, PaCO2 40 mm Hg, HCO3- 29 mEq/L

Answer

pH 7.28, PaCO2 55 mm Hg, HCO3- 24 mEq/L
The correct answer displays uncompensated respiratory acidosis. The hypoventilation caused by the opioid overdose leads to rapid CO2 retention (PaCO2 55 mm Hg). This excess CO2 lowers the blood pH (pH 7.28). Because this is an acute event, the kidneys have not yet had time to compensate, so the bicarbonate (HCO3-) remains normal (24 mEq/L).

Step-by-Step Solution

1
Identify the client's primary physiological problem based on the clinical presentation.
The client has a respiratory rate of 8 breaths per minute due to an opioid overdose, which indicates severe hypoventilation.
Opioids are central nervous system depressants that decrease the respiratory drive.
2
Determine the effect of hypoventilation on carbon dioxide (CO2) levels in the blood.
Hypoventilation causes the lungs to retain CO2, leading to hypercapnia (an elevated PaCO2 > 45 mm Hg).
CO2 is an acidic compound; when it is not adequately exhaled, it accumulates in the bloodstream.
3
Correlate the CO2 accumulation with the expected change in blood pH.
The retained CO2 increases blood acidity, resulting in a low pH (acidosis).
An elevated PaCO2 directly lowers the pH, creating a state of respiratory acidosis. Because this is an acute event, the bicarbonate (HCO3-) remains within the normal range of 22-26 mEq/L.

Key Concept

Respiratory Acidosis secondary to Hypoventilation
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Topics

Physiological Adaptation

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