ABG shows pH 7.32, PaCO2 50 mmHg, HCO3- 26 mEq/L. What is the primary disturbance?

ABG shows pH 7.32, PaCO2 50 mmHg, HCO3- 26 mEq/L. What is the primary disturbance?

• A. Metabolic acidosis with respiratory compensation
• B. Metabolic alkalosis
• C. Respiratory acidosis with partial metabolic compensation
• D. Respiratory alkalosis

Answer: (C)

The key idea is that ABG changes show the primary disorder by looking at the acid-base driver (PaCO2) and whether bicarbonate (HCO3-) has adjusted to compensate. Here, the pH is acidic (7.32), indicating acidemia. The PaCO2 is elevated at 50 mmHg, pointing to a respiratory cause—hypoventilation leading to CO2 buildup. For a respiratory disorder, the body compensates metabolically by raising HCO3- to buffer the excess acid. The HCO3- is 26 mEq/L, which is on the high end of normal but only modestly elevated, suggesting an incomplete (partial) metabolic compensation rather than full compensation. So the pattern is respiratory acidosis with partial metabolic compensation: the primary problem is elevated CO2 causing acidemia, and the bicarbonate has begun to compensate but has not fully normalized the pH. If compensation were complete and the process chronic, you’d expect a larger rise in HCO3- and a near-normal pH; if there were a metabolic primary issue, the PaCO2 would not be elevated in the same way.

The key idea is that ABG changes show the primary disorder by looking at the acid-base driver (PaCO2) and whether bicarbonate (HCO3-) has adjusted to compensate.

Here, the pH is acidic (7.32), indicating acidemia. The PaCO2 is elevated at 50 mmHg, pointing to a respiratory cause—hypoventilation leading to CO2 buildup. For a respiratory disorder, the body compensates metabolically by raising HCO3- to buffer the excess acid. The HCO3- is 26 mEq/L, which is on the high end of normal but only modestly elevated, suggesting an incomplete (partial) metabolic compensation rather than full compensation.

So the pattern is respiratory acidosis with partial metabolic compensation: the primary problem is elevated CO2 causing acidemia, and the bicarbonate has begun to compensate but has not fully normalized the pH. If compensation were complete and the process chronic, you’d expect a larger rise in HCO3- and a near-normal pH; if there were a metabolic primary issue, the PaCO2 would not be elevated in the same way.