Lab values: pH 7.56, paCO2- 20, HCO3- 20 .Interpret?
**Core Concept**
Metabolic alkalosis is a condition characterized by an increase in blood pH, often resulting from an imbalance in acid-base equilibrium. This occurs when there is a net loss of hydrogen ions or an increase in bicarbonate ions.
**Why the Correct Answer is Right**
The given lab values (pH 7.56, paCO2 20, HCO3- 20) indicate a primary metabolic alkalosis. The paCO2 is low, suggesting that the respiratory system is compensating for the alkalosis by exhaling more CO2. However, the HCO3- level is also elevated, indicating that the metabolic component of the alkalosis is the primary cause. In metabolic alkalosis, the kidneys conserve bicarbonate ions and excrete hydrogen ions to maintain acid-base balance.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the given lab values do not indicate a respiratory alkalosis, which would be characterized by an elevated paCO2.
**Option B:** This option is incorrect because the paCO2 is low, indicating that the respiratory system is compensating for a metabolic alkalosis, not a respiratory acidosis.
**Option C:** This option is incorrect because the HCO3- level is elevated, indicating a metabolic component to the alkalosis, not a simple respiratory alkalosis.
**Clinical Pearl / High-Yield Fact**
In metabolic alkalosis, the kidneys play a key role in maintaining acid-base balance by conserving bicarbonate ions and excreting hydrogen ions. This can be remembered using the mnemonic "HCO3- goes up, H+ goes down."
**Correct Answer: D. Metabolic alkalosis.**