Which finding is characteristic of metabolic acidosis?

Which finding is characteristic of metabolic acidosis?

• A. PH < 7.35 with high bicarbonate and a normal anion gap
• B. PH < 7.35 with low bicarbonate and elevated anion gap
• C. PH > 7.45 with low bicarbonate
• D. PH < 7.35 with high CO2

Answer: (B)

Metabolic acidosis is defined by a low pH with a reduced bicarbonate level. When the anion gap is elevated, it indicates accumulation of unmeasured anions (high anion gap metabolic acidosis), such as lactic acidosis or ketoacidosis. The finding that best fits this pattern shows acidemia with a low bicarbonate and an elevated anion gap, aligning with metabolic acidosis due to increased unmeasured anions. The other scenarios don’t fit: high bicarbonate with acidemia would point away from metabolic acidosis (more like metabolic alkalosis or a mixed disorder); acidemia with high CO2 indicates respiratory acidosis; alkalemia with low bicarbonate doesn’t reflect a primary metabolic acidosis.

Metabolic acidosis is defined by a low pH with a reduced bicarbonate level. When the anion gap is elevated, it indicates accumulation of unmeasured anions (high anion gap metabolic acidosis), such as lactic acidosis or ketoacidosis. The finding that best fits this pattern shows acidemia with a low bicarbonate and an elevated anion gap, aligning with metabolic acidosis due to increased unmeasured anions.

The other scenarios don’t fit: high bicarbonate with acidemia would point away from metabolic acidosis (more like metabolic alkalosis or a mixed disorder); acidemia with high CO2 indicates respiratory acidosis; alkalemia with low bicarbonate doesn’t reflect a primary metabolic acidosis.