Which of the following is a cause of high anion gap metabolic acidosis due to unmeasured anions?

• A. Paraldehyde
• B. Hypoalbuminemia
• C. Hyperchloremia
• D. Saline infusion

Answer: (A)

High anion gap metabolic acidosis happens when unmeasured anions accumulate in the blood, widening the difference Na − (Cl + HCO3). These unmeasured anions come from organic acids produced during metabolism or toxin ingestions (lactate, ketoacids, sulfates, phosphates, etc.), not captured by routine electrolyte panels. Paraldehyde, especially in overdose, is metabolized to acids that are not part of the standard measurements, so they add to the unmeasured anions and raise the anion gap. In contrast, hypoalbuminemia reduces the anion gap because albumin contributes to the unmeasured negative charge; hyperchloremia from saline infusion adds chloride and drives a normal or low anion gap metabolic acidosis rather than a high one.