In a patient with respiratory distress and metabolic acidosis, what laboratory finding is typically elevated?

In a patient experiencing respiratory distress accompanied by metabolic acidosis, the laboratory finding that is typically elevated is the concentration of hydrogen ions (H+). Metabolic acidosis is characterized by an increase in H+ ions due to a variety of factors, such as increased acid production or decreased acid excretion by the kidneys.

When the body enters a state of metabolic acidosis, it attempts to compensate for the increased acidity by increasing respiratory rate, which helps to reduce carbon dioxide (PCO2) levels through hyperventilation. However, the primary factor in metabolic acidosis is the accumulation of H+ ions, which directly impacts blood pH by lowering it. Thus, measuring H+ concentration can provide significant insight into the severity of the acidosis.

The other laboratory values mentioned generally do not show an increase in this scenario. For example, PCO2 would typically decrease as a compensatory response rather than be elevated. Serum bicarbonate often shows a decrease in metabolic acidosis, and blood pH is likely to be lower than normal due to the acidotic state.

Therefore, the elevation of H+ concentration is the hallmark finding in metabolic acidosis, making it the correct answer in this context.