In uncompensated metabolic alkalosis, which value is typically near normal?

• A. PaCO2 near normal
• B. pH near normal
• C. HCO3 near normal
• D. PaO2 near normal

Answer: (A)

In uncompensated metabolic alkalosis, the primary abnormality is an elevated bicarbonate that raises the pH, and the respiratory system hasn’t yet adjusted. Because there’s no respiratory compensation at this stage, the PaCO2 tends to stay within the normal range rather than being elevated or depressed. The bicarbonate rise drives the alkalosis, and pH is high while PaCO2 remains near normal until the body begins to compensate. PaO2 is usually normal unless another issue affects oxygenation, so the value that stays near normal in this situation is PaCO2.