Which of the following is a classic cause of increased anion gap metabolic acidosis?

• A. Lactic acidosis
• B. Hyperchloremic acidosis
• C. Hypoalbuminemia
• D. Sodium overload

Answer: (A)

An elevated anion gap in metabolic acidosis points to the buildup of unmeasured anions in the blood. Lactate is the classic unmeasured anion that accumulates in many conditions, so lactic acidosis reliably produces a high anion gap. This occurs with tissue hypoxia or impaired lactate clearance, such as in shock, sepsis, severe anemia, or mitochondrial dysfunction, making it the典ical example of high anion gap metabolic acidosis.

Hyperchloremic acidosis, by contrast, is a normal anion gap acidosis because chloride rises as bicarbonate is lost, keeping the gap unchanged. Hypoalbuminemia lowers the gap since albumin contributes to the unmeasured anions; with less albumin, the gap decreases. Sodium overload does not specifically drive an increase in the anion gap.