Given Na 140, Cl 110, HCO3 8, what is the anion gap and the most likely class of metabolic acidosis?

• A. Anion gap 24; high-anion-gap metabolic acidosis
• B. Anion gap 22; high-anion-gap metabolic acidosis
• C. Anion gap 6; normal
• D. Anion gap 14; lactic acidosis

Answer: (B)

The key idea is using the anion gap to classify metabolic acidosis. The anion gap is calculated as Na − (Cl + HCO3). With Na 140, Cl 110, and HCO3 8, the gap is 140 − (110 + 8) = 22 mEq/L. Normal is roughly 8–12, so 22 is clearly elevated, indicating a high anion gap metabolic acidosis. The low bicarbonate confirms metabolic acidosis is present. A high anion gap points to accumulation of unmeasured anions such as lactate, ketoacids, or certain toxins. Among the given descriptions, the one that matches an anion gap of about 22 and identifies a high-anion-gap metabolic acidosis best fits the data. The other options either misstate the calculated gap (e.g., a normal or a much lower gap) or describe a different classification not consistent with the calculated value and low bicarbonate.