A nurse is reviewing arterial blood gas results for a client who has metabolic acidosis. Which of the following values should the nurse expect?

Arterial blood gas (ABG) analysis is used to evaluate acid-base balance and respiratory function. Metabolic acidosis occurs when there is a primary decrease in serum bicarbonate due to excess acid production or loss of bicarbonate from the body. The respiratory system may compensate by increasing ventilation to reduce carbon dioxide levels. Interpreting ABG values requires identifying the primary disturbance and expected compensatory changes. Rationale: A. PaO₂ 64 mm Hg indicates hypoxemia, which is related to oxygenation status rather than acid-base balance. Although respiratory compromise may coexist with metabolic disorders, a low PaO₂ is not a defining characteristic of metabolic acidosis. Therefore, this value does not directly reflect the expected acid-base disturbance. B. HCO₃⁻ 20 mEq/L is decreased and is the primary abnormality seen in metabolic acidosis. Bicarbonate acts as a buffer, and its reduction indicates accumulation of acid or loss of base. This finding confirms the metabolic origin of the acid-base imbalance and is the expected laboratory result. C. PaCO₂ 32 mm Hg represents respiratory compensation rather than the primary disorder. In metabolic acidosis, the lungs attempt to correct pH by increasing respiratory rate to blow off carbon dioxide. Although this is an expected compensatory change, it is not the primary abnormal value. D. pH 7.48 indicates alkalosis, not acidosis. In metabolic acidosis, the pH would be decreased (below 7.35). Therefore, this value is inconsistent with the condition described and does not represent the expected ABG finding.