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Difficulty: EasyPhysiological Adaptation

A nurse is evaluating the arterial blood gas (ABG) results for a client who is admitted to the medical-surgical unit with a diagnosis of diabetic ketoacidosis. The laboratory report shows a pH of 7.287.28, a PaCO2\text{PaCO}_2 of 38 mm Hg38\text{ mm Hg}, and an HCO3−\text{HCO}_3^- of 15 mEq/L15\text{ mEq/L}. Based on these values, which of the following acid-base imbalances is this client experiencing?

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

Answer

The correct answer is metabolic acidosis.
The client's pH is below the normal range of 7.357.35 to 7.457.45, indicating acidosis. The HCO3−\text{HCO}_3^- is below the normal range of 2222 to 26 mEq/L26\text{ mEq/L}, pointing to a metabolic origin. The PaCO2\text{PaCO}_2 is within the normal range of 3535 to 45 mm Hg45\text{ mm Hg}, demonstrating that there is no respiratory compensation yet. Therefore, this represents uncompensated metabolic acidosis, a classic finding in diabetic ketoacidosis.

Step-by-Step Solution

1
Analyze the pH value to determine if the primary state is acidosis or alkalosis.
The pH is 7.287.28, which is less than the normal minimum of 7.357.35, indicating acidemia (acidosis).
Determining the overall acid-base status (pH) is always the first step in ABG interpretation.
2
Evaluate the PaCO2\text{PaCO}_2 value to check for a respiratory cause.
The PaCO2\text{PaCO}_2 is 38 mm Hg38\text{ mm Hg}, which falls within the normal range of 3535 to 45 mm Hg45\text{ mm Hg}.
The PaCO2\text{PaCO}_2 indicates the respiratory component of the acid-base balance.
3
Assess the HCO3−\text{HCO}_3^- value to check for a metabolic cause.
The HCO3−\text{HCO}_3^- is 15 mEq/L15\text{ mEq/L}, which is significantly lower than the normal range of 2222 to 26 mEq/L26\text{ mEq/L}.
The HCO3−\text{HCO}_3^- represents the metabolic component of the acid-base balance.
4
Synthesize the findings to determine the primary imbalance and compensation status.
Since the pH indicates acidosis and the HCO3−\text{HCO}_3^- is low (which causes acidosis), the primary imbalance is metabolic acidosis. The normal PaCO2\text{PaCO}_2 indicates the condition is uncompensated.
Matching the abnormal parameter to the pH state identifies the origin of the imbalance.

Key Concept

Interpretation of uncompensated metabolic acidosis using arterial blood gas (ABG) values.
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Topics

Physiological Adaptation

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