A client’s ABG results are as follows: pH: 7.16; PaCO2 80 mm Hg; PaO2 46 mm Hg; HCO3- 24 mEq/L; SaO2 81%. This ABG result represents which of the following conditions?
A. Metabolic acidosis
B. Metabolic alkalosis
C. Respiratory acidosis
D. Respiratory alkalosis
Correct Answer: C. Respiratory acidosis
PaCO2 > 40 with a pH < 7.4 indicates a respiratory acidosis. If the pH is in the normal range (7.35-7.45), use a pH of 7.40 as a cutoff point. In other words, a pH of 7.37 would be categorized as acidosis. Arterial blood gas interpretation is best approached systematically. Interpretation leads to an understanding of the degree or severity of abnormalities, whether the abnormalities are acute or chronic, and if the primary disorder is metabolic or respiratory in origin.
Option A: Evaluate the respiratory and metabolic components of the ABG results, the PaCO2 and HCO3, respectively. The PaCO2 indicates whether the acidosis or alkalemia is primarily from a respiratory or metabolic acidosis/alkalosis.
Option B: The acid-base that is inconsistent with the pH is the HCO3, as it is elevated, indicating a metabolic alkalosis, so there is compensation signifying a non-acute primary disorder because it takes days for metabolic compensation to be effective.
Option D: PaCO2 < 40 and pH < 7.4 indicates a respiratory alkalosis (but is often from hyperventilation from anxiety or compensation for a metabolic acidosis). Assess for evidence of compensation for the primary acidosis or alkalosis by looking for the value (PaCO2 or HCO3) that is not consistent with the pH.
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