A nurse is caring for a patient who has acute kidney injury.
The patient’s ABGs are: pH: 7.26, PaCO2: 30 mm Hg, HCO3: 14 mEq/L. Which of the following acid-base imbalances should the nurse identify the patient is experiencing?

Choice A rationale:

Metabolic alkalosis is characterized by a high pH (above 7.45), high bicarbonate (HCO3-) levels, and normal or low PaCO2. The patient's ABGs show a low pH (7.26), low bicarbonate (14 mEq/L), and low PaCO2 (30 mm Hg), which are not consistent with metabolic alkalosis.

Choice C rationale:

Respiratory alkalosis is characterized by a high pH (above 7.45), low PaCO2, and normal or slightly elevated bicarbonate levels. The patient's ABGs do show a low PaCO2, but the pH is low (acidic) and the bicarbonate is low, which are not consistent with respiratory alkalosis.

Choice D rationale:

Respiratory acidosis is characterized by a low pH (below 7.35), high PaCO2, and normal or slightly elevated bicarbonate levels. The patient's ABGs do show a low pH, but the PaCO2 is also low, which is not consistent with respiratory acidosis.

Rationale for the correct answer, B:

Metabolic acidosis is characterized by a low pH (below 7.35), low bicarbonate levels, and normal or low PaCO2. The patient's ABGs are consistent with metabolic acidosis because they show a low pH (7.26), low bicarbonate (14 mEq/L), and low PaCO2 (30 mm Hg).

Acute kidney injury is a common cause of metabolic acidosis. The kidneys play a vital role in regulating acid-base balance by excreting acids and reabsorbing bicarbonate. When the kidneys are damaged, they are unable to excrete acids effectively, leading to an accumulation of acids in the blood and a decrease in bicarbonate levels.

Additional Information:

It's important to note that the patient's low PaCO2 is likely a compensatory mechanism for the metabolic acidosis. In response to acidosis, the respiratory system tries to increase ventilation to blow off more carbon dioxide, which helps to raise the pH. However, this compensatory mechanism is often not enough to fully correct the acidosis.

Choice A rationale:

Respiratory acidosis is characterized by a low pH (less than 7.35), a high PaCO2 (greater than 45 mm Hg), and a normal or high HCO3 (22-26 mEq/L). It occurs when there is a buildup of carbon dioxide in the blood due to impaired ventilation.

The patient's ABGs do not align with respiratory acidosis because the pH is elevated (7.6), and the PaCO2 is within the normal range (40 mm Hg).

Choice B rationale:

Respiratory alkalosis is characterized by a high pH (greater than 7.45), a low PaCO2 (less than 35 mm Hg), and a normal or low HCO3 (22-26 mEq/L). It occurs when there is excessive loss of carbon dioxide through hyperventilation.

The patient's ABGs do not align with respiratory alkalosis because the HCO3 is elevated (32 mEq/L), which is not typical for this condition.

Choice C rationale:

Metabolic acidosis is characterized by a low pH (less than 7.35), a normal or low PaCO2 (less than 40 mm Hg), and a low HCO3 (less than 22 mEq/L). It occurs when there is an excess of acid in the body or a loss of bicarbonate.

The patient's ABGs do not align with metabolic acidosis because the pH is elevated (7.6), and the HCO3 is elevated (32 mEq/L).

Choice D rationale:

Metabolic alkalosis is characterized by a high pH (greater than 7.45), a normal or high PaCO2 (40-45 mm Hg), and an elevated HCO3 (greater than 26 mEq/L). It occurs when there is an excess of bicarbonate in the body or a loss of acid.

The patient's ABGs align with metabolic alkalosis because of the high pH (7.6), normal PaCO2 (40 mm Hg), and elevated HCO3 (32 mEq/L).