The nurse admits a patient and performs an arterial blood gas. The results are:

pH 7.51
PCO2: 49
PO2: 85
HCO3: 35

Which choice describes this arterial blood gas result?

A. Compensated respiratory acidosis
B. Uncompensated metabolic acidosis
C. Uncompensated metabolic alkalosis
D. Partially compensated metabolic alkalosis

D, Partially compensated metabolic alkalosis is the correct answer.

There is an increase in pH, which indicates alkalosis and an increase in HCO3, which indicates that the cause is metabolic.

If the PH is up and the HCO3 is up, then it is metabolic alkalosis.

If the PH is down and the HCO3 is down, then it is metabolic acidosis.

Notice the pattern? With metabolic, the PH and HCO3 follow each other. With respiratory, it is the opposite.

ROME: Respiratory is opposite, metabolic is equal.
In respiratory acidosis, the respiratory system is the cause. If there is an increase in PCO2, there is a decrease in pH.

Just like in ROME, respiratory results are opposite. When one is up, the other one is down. Compensation means that the kidneys resabsorb bicarb (HCO3).

Respiratory alkalosis is caused by excessive ventilation. If there is a decrease in PCO2, there will be an increase in pH. Respiratory results are opposite.

The compensation is when kidneys excrete HCO3.

Metabolic acidosis is caused by the loss of bicarb or a buildup of acids. This is not caused by respiration. It can be caused by lactic acidosis, diarrhea, renal failure, ketones, or ammonium intoxication.

Compensation is due to hyperventilation to eliminate CO2.

Metabolic alkalosis is when the acid is lost from emesis or diuretics. This can be caused by retention of HCO3 from medications or hyperaldosteronism. When there is an increase in HCO3, there is an increase in pH because metabolic is equal.

Compensation is when the respiratory centers are not stimulated, causing hypoventilation and CO2 retention.