Which acid-base pattern is consistent with metabolic acidosis?

Which acid-base pattern is consistent with 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 occurs when there is a loss of bicarbonate or an excess of acid, causing hydrogen ions to rise and the pH to fall. The body tries to compensate by increasing respiration to blow off CO2, so the PaCO2 tends to decrease. Therefore, the pattern that fits metabolic acidosis is a low pH with a low bicarbonate level. The respiratory system may lower PaCO2 as compensation, but the key clue is the reduced HCO3- accompanying acidemia. The other patterns point to different disturbances: high pH with high bicarbonate suggests metabolic alkalosis; low pH with high PaCO2 indicates respiratory acidosis; a low pH with low PaCO2 could occur with compensation, but the direct hallmark of metabolic acidosis is low pH with low HCO3-.

Metabolic acidosis occurs when there is a loss of bicarbonate or an excess of acid, causing hydrogen ions to rise and the pH to fall. The body tries to compensate by increasing respiration to blow off CO2, so the PaCO2 tends to decrease.

Therefore, the pattern that fits metabolic acidosis is a low pH with a low bicarbonate level. The respiratory system may lower PaCO2 as compensation, but the key clue is the reduced HCO3- accompanying acidemia.

The other patterns point to different disturbances: high pH with high bicarbonate suggests metabolic alkalosis; low pH with high PaCO2 indicates respiratory acidosis; a low pH with low PaCO2 could occur with compensation, but the direct hallmark of metabolic acidosis is low pH with low HCO3-.