Saunders Respiratory Practice

Which arterial blood gas result indicates metabolic alkalosis?

1. pH of 7.35, Pco2 of 44 mm Hg, HCO3- of 24 mEq/L

2. pH of 7.48, Pco2 of 40 mm Hg, HCO3- of 36 mEq/L

3. pH of 7.43, Pco2 of 38 mm Hg, HCO3- of 22 mEq/L

4. pH of 7.29, Pco2 of 55 mm Hg, HCO3- of 18 mEq/L

The correct answer is: pH of 7.48, Pco2 of 40 mm Hg, HCO3- of 36 mEq/L

To assess which arterial blood gas result indicates metabolic alkalosis, it is crucial to examine the key components: pH, carbon dioxide concentration (Pco2), and bicarbonate concentration (HCO3-). In metabolic alkalosis, the pH is elevated above the normal range (7.35-7.45), and there is an increased bicarbonate level (HCO3-). Evaluating the provided results, the scenario with a pH of 7.48 is indicative of alkalosis, as it is above the normal upper limit of 7.45. Furthermore, the HCO3- level in this result is 36 mEq/L, which is elevated compared to the normal range (22-26 mEq/L). This combination of an elevated pH and increased bicarbonate concentration is characteristic of metabolic alkalosis. The Pco2 in this result is within the normal range, indicating that the alkalosis is metabolic rather than respiratory. Other choices demonstrate different scenarios: one indicates normal acid-base balance with a normal pH and bicarbonate, while others indicate acidosis due to low pH and, in one case, a high Pco2, which suggests respiratory acidosis rather than metabolic alkalosis.