Which ABG pattern is expected in metabolic acidosis?

Which ABG pattern is expected in metabolic acidosis?

• A. Low pH and low HCO3
• B. High pH and high HCO3
• C. Normal pH with normal HCO3
• D. Low pH and high HCO3

Answer: (A)

Metabolic acidosis arises when bicarbonate (the primary base in the blood) is lost or overwhelmed by acid, so HCO3- falls. That reduced buffering pushes hydrogen ions up and pH drops. To compensate, the lungs rapidly blow off CO2, helping to raise pH, so the PCO2 is decreased. The resulting ABG pattern is a low pH with a low HCO3-, reflecting the metabolic origin with respiratory compensation. The other patterns point to a different disturbance: high pH with high HCO3- is metabolic alkalosis, normal pH and HCO3- means no disturbance, and low pH with high HCO3- would suggest a mixed disorder or timing of compensation rather than pure metabolic acidosis.

Metabolic acidosis arises when bicarbonate (the primary base in the blood) is lost or overwhelmed by acid, so HCO3- falls. That reduced buffering pushes hydrogen ions up and pH drops. To compensate, the lungs rapidly blow off CO2, helping to raise pH, so the PCO2 is decreased. The resulting ABG pattern is a low pH with a low HCO3-, reflecting the metabolic origin with respiratory compensation. The other patterns point to a different disturbance: high pH with high HCO3- is metabolic alkalosis, normal pH and HCO3- means no disturbance, and low pH with high HCO3- would suggest a mixed disorder or timing of compensation rather than pure metabolic acidosis.