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Difficulty: EasyPhysiological Adaptation

An older adult client is hospitalized after a severe bout of gastroenteritis with frequent liquid stools over the last three days. The laboratory reports the following arterial blood gas values: pH 7.297.29, PaCO2PaCO_2 42 mm Hg42\text{ mm Hg}, and HCO3−HCO_3^- 17 mEq/L17\text{ mEq/L}. Based on these results, which primary acid-base imbalance should the nurse identify?

  1. Metabolic acidosisAnswer
  2. B
    Metabolic alkalosis
  3. C
    Respiratory acidosis
  4. D
    Respiratory alkalosis

Answer

The client is experiencing metabolic acidosis.
The correct answer is metabolic acidosis because the arterial blood gas results show a low pH (7.297.29), indicating acidosis, paired with a low bicarbonate level (17 mEq/L17\text{ mEq/L}). The normal PaCO2PaCO_2 (42 mm Hg42\text{ mm Hg}) confirms that the primary disturbance is metabolic, which aligns with the clinical history of excessive lower gastrointestinal bicarbonate loss through severe diarrhea.

Step-by-Step Solution

1
Analyze the pH value to determine the primary state.
The pH is 7.297.29, which is less than the normal range of 7.357.35 to 7.457.45.
A pH below 7.357.35 defines acidemia (acidosis).
2
Analyze the PaCO2PaCO_2 value to check for respiratory involvement.
The PaCO2PaCO_2 is 42 mm Hg42\text{ mm Hg}, which is within the normal range of 3535 to 45 mm Hg45\text{ mm Hg}.
A normal PaCO2PaCO_2 rules out a primary respiratory disturbance as the cause of the acidosis.
3
Analyze the HCO3−HCO_3^- value to check for metabolic involvement.
The HCO3−HCO_3^- is 17 mEq/L17\text{ mEq/L}, which is less than the normal range of 2222 to 26 mEq/L26\text{ mEq/L}.
A decreased HCO3−HCO_3^- level directly corresponds with the acidic pH, confirming a metabolic origin.

Key Concept

Interpretation of uncompensated acid-base imbalances using arterial blood gas values.
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Topics

Physiological Adaptation

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