ABG with pH 7.25, PCO2 56, HCO3- 16 indicates:

ABG with pH 7.25, PCO2 56, HCO3- 16 indicates:

• A. Metabolic alkalosis, partially compensated
• B. Respiratory acidosis, uncompensated
• C. A dual problem of acidosis
• D. An error in measurement

Answer: (C)

The key idea is recognizing acidemia and parsing whether the disturbance is respiratory, metabolic, or mixed. Here the pH is 7.25, which shows acidemia. The elevated PCO2 of 56 indicates respiratory acidosis because CO2 retention causes the blood to become more acidic. At the same time, the low bicarbonate level of 16 mEq/L points to metabolic acidosis, since a loss of HCO3– or an increased acid load lowers the bicarbonate. In a single disorder, the secondary value would move in a compensatory direction: respiratory acidosis tends to raise HCO3– through renal compensation, while metabolic acidosis tends to lower PCO2 through respiratory compensation. The fact that you have both an elevated CO2 and a reduced HCO3– means neither abnormality alone can account for the acidemia; both are present as primary problems. The result is a mixed disorder—simultaneous respiratory acidosis and metabolic acidosis—producing a more pronounced acidemia, which is why this situation is described as a dual problem of acidosis.

The key idea is recognizing acidemia and parsing whether the disturbance is respiratory, metabolic, or mixed. Here the pH is 7.25, which shows acidemia. The elevated PCO2 of 56 indicates respiratory acidosis because CO2 retention causes the blood to become more acidic. At the same time, the low bicarbonate level of 16 mEq/L points to metabolic acidosis, since a loss of HCO3– or an increased acid load lowers the bicarbonate.

In a single disorder, the secondary value would move in a compensatory direction: respiratory acidosis tends to raise HCO3– through renal compensation, while metabolic acidosis tends to lower PCO2 through respiratory compensation. The fact that you have both an elevated CO2 and a reduced HCO3– means neither abnormality alone can account for the acidemia; both are present as primary problems. The result is a mixed disorder—simultaneous respiratory acidosis and metabolic acidosis—producing a more pronounced acidemia, which is why this situation is described as a dual problem of acidosis.