pH = 7.27, HCO3= 10 mEq/dl and pC02 = 23 mm Hg:
**Core Concept**
The given arterial blood gas (ABG) values indicate a mixed acid-base disorder, specifically a combination of metabolic acidosis and respiratory alkalosis. The pH is low, indicating acidemia, while the bicarbonate (HCO3-) level is low, suggesting a metabolic component. The low PCO2 level indicates a respiratory component.
**Why the Correct Answer is Right**
The low PCO2 level suggests that the patient is hyperventilating, leading to a respiratory alkalosis. The low HCO3- level indicates a metabolic acidosis. The combination of these two disorders results in a mixed acid-base disorder. The kidneys compensate for the metabolic acidosis by retaining more HCO3-, but the respiratory alkalosis overshadows this compensation, resulting in a net acid-base disturbance. The kidneys also produce more ammonium (NH4+) to help eliminate excess hydrogen ions, but this is not sufficient to correct the acidosis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option does not account for the mixed acid-base disorder. A respiratory acidosis would have a high PCO2 level, not a low one.
**Option B:** This option only addresses the respiratory alkalosis and does not account for the metabolic acidosis.
**Option C:** This option only addresses the metabolic acidosis and does not account for the respiratory alkalosis.
**Clinical Pearl / High-Yield Fact**
In mixed acid-base disorders, the primary disorder (in this case, the respiratory alkalosis) overshadows the compensatory response to the secondary disorder (the metabolic acidosis). Therefore, the primary disorder should be addressed first.
**Correct Answer: B. Respiratory alkalosis with metabolic acidosis.**