A nurse is caring for a client whose arterial blood gas results show a pH of 7.3 and a Paco2 of 50 mm Hg. The nurse should identify that the client is experiencing which of the following acid-base imbalances?
A.
Respiratory acidosis.
B.
Metabolic acidosis.
C.
Metabolic alkalosis.
D.
Respiratory alkalosis.
The Correct Answer and Explanation is:
The correct answer is A. Respiratory acidosis.
To understand why this is the case, let’s break down the arterial blood gas (ABG) results provided:
- pH: A pH of 7.3 indicates that the blood is more acidic than normal. The normal pH range for arterial blood is between 7.35 and 7.45. A pH below 7.35 suggests acidemia, meaning the blood is too acidic.
- PaCO2: The partial pressure of carbon dioxide (PaCO2) is 50 mm Hg. The normal PaCO2 range is between 35 and 45 mm Hg. A PaCO2 level above 45 mm Hg indicates hypercapnia, or elevated CO2 levels, which can lead to increased acidity in the blood.
In respiratory acidosis, the primary problem is an increase in PaCO2 due to impaired gas exchange in the lungs. When CO2 levels increase, it reacts with water in the blood to form carbonic acid, which dissociates into hydrogen ions (H+) and bicarbonate (HCO3-), leading to a decrease in blood pH. This type of acid-base imbalance is usually caused by conditions that impair the ability to expel CO2 from the lungs, such as chronic obstructive pulmonary disease (COPD), severe asthma, or respiratory depression.
To confirm respiratory acidosis, we look at the ABG results:
- The pH is low (7.3), indicating acidity.
- The PaCO2 is high (50 mm Hg), indicating an excess of CO2.
The elevated PaCO2 is causing the pH to decrease, which fits the profile of respiratory acidosis.
Other choices:
- B. Metabolic acidosis involves a low pH with a low HCO3- (bicarbonate) level, which is not indicated by the provided data.
- C. Metabolic alkalosis would show a high pH and high HCO3-, not applicable here.
- D. Respiratory alkalosis would show a high pH and low PaCO2, the opposite of what is presented.
Thus, the client is experiencing respiratory acidosis.