Which ABG pattern defines metabolic acidosis?

Which ABG pattern defines metabolic acidosis?

• A. Low pH with low HCO3-
• B. High pH with high HCO3-
• C. Low pH with high PaCO2
• D. Low pH with low PaCO3

Answer: (A)

Metabolic acidosis shows a fall in both pH and bicarbonate (HCO3-). The body often tries to compensate by blowing off CO2, so the PaCO2 may be lower, but the key defining change is the low HCO3-. That’s why a pattern with low pH and low HCO3- is the correct depiction of metabolic acidosis. The other patterns point to different disorders: low pH with high PaCO2 indicates respiratory acidosis; high pH with high HCO3- indicates metabolic alkalosis; a low pH with low PaCO2 isn’t the defining pattern for metabolic acidosis.

Metabolic acidosis shows a fall in both pH and bicarbonate (HCO3-). The body often tries to compensate by blowing off CO2, so the PaCO2 may be lower, but the key defining change is the low HCO3-. That’s why a pattern with low pH and low HCO3- is the correct depiction of metabolic acidosis.

The other patterns point to different disorders: low pH with high PaCO2 indicates respiratory acidosis; high pH with high HCO3- indicates metabolic alkalosis; a low pH with low PaCO2 isn’t the defining pattern for metabolic acidosis.