The nurse is caring for a hospitalized client who is retaining carbon dioxide (CO2) because of respiratory disease. The nurse anticipates which physical response will initially occur?

A. The client's sodium and chloride levels will rise: CO₂ retention affects acid-base balance more directly than it affects electrolyte concentrations like sodium or chloride. Changes in these levels may occur in severe or chronic cases, but they are not the initial response. B. The client's arterial blood gas results will reflect acidosis: When CO₂ accumulates in the blood due to hypoventilation, it forms carbonic acid, lowering blood pH. This results in respiratory acidosis, which is typically the earliest and most direct physiological response to CO₂ retention. C. The client will lose consciousness: Loss of consciousness may occur if CO₂ levels rise dramatically and go uncorrected. However, this is a late sign of severe respiratory failure, not the initial or most sensitive indicator. D. The client will complain of facial numbness and tingling: These symptoms are more characteristic of respiratory alkalosis, often due to hyperventilation, not CO₂ retention. In respiratory acidosis, symptoms are more likely to include drowsiness, confusion, or headache.