In acid-base assessment, a HCO3- + AG − 12 value greater than 30 indicates what?

In acid-base assessment, a HCO3- + AG − 12 value greater than 30 indicates what?

• A. Respiratory alkalosis
• B. No acid-base disturbance
• C. Underlying metabolic alkalosis
• D. Nonanion gap metabolic acidosis

Answer: (C)

The key idea is using the delta value HCO3- plus the anion gap to detect a mixed acid-base process. In a normal situation, bicarbonate is about 24 and the anion gap is about 12, so this sum minus 12 comes out around 24. When this value climbs above 30, it signals there is more base (bicarbonate) present than would be expected from the primary disturbance alone, pointing to an additional metabolic alkalosis on top of whatever else is occurring. In other words, there’s an underlying metabolic alkalosis contributing to the overall picture.

The key idea is using the delta value HCO3- plus the anion gap to detect a mixed acid-base process. In a normal situation, bicarbonate is about 24 and the anion gap is about 12, so this sum minus 12 comes out around 24. When this value climbs above 30, it signals there is more base (bicarbonate) present than would be expected from the primary disturbance alone, pointing to an additional metabolic alkalosis on top of whatever else is occurring. In other words, there’s an underlying metabolic alkalosis contributing to the overall picture.