Which combination indicates metabolic acidosis on ABG?

Which combination indicates metabolic acidosis on ABG?

• A. Low pH, low HCO3, normal PCO2
• B. High pH, high HCO3, high PCO2
• C. Low pH, high HCO3, low PCO2
• D. High pH, low HCO3, low PCO2

Answer: (A)

Metabolic acidosis shows a primary drop in bicarbonate (HCO3−) with acidemia (low pH). The body tries to compensate by blowing off CO2, so the PCO2 tends to decrease. When you see a low pH and low HCO3− with a normal PCO2, this can reflect an acute, uncompensated metabolic acidosis. The other patterns either point to alkalosis (high pH with high HCO3− or high PCO2) or a mixed disorder, which don’t fit isolated metabolic acidosis.

Metabolic acidosis shows a primary drop in bicarbonate (HCO3−) with acidemia (low pH). The body tries to compensate by blowing off CO2, so the PCO2 tends to decrease. When you see a low pH and low HCO3− with a normal PCO2, this can reflect an acute, uncompensated metabolic acidosis. The other patterns either point to alkalosis (high pH with high HCO3− or high PCO2) or a mixed disorder, which don’t fit isolated metabolic acidosis.