A patient’s arterial blood gas (ABG) values include a pH of 7.48, a PaCO2 of 38, and an HCO3- of 30. Around which acid-base imbalance would the nurse plan the patient’s care?
A.
Metabolic acidosis.
B.
Metabolic alkalosis.
C.
Respiratory acidosis.
D.
Respiratory alkalosis.
The Correct Answer and Explanation is:
The correct answer is B. Metabolic alkalosis.
Explanation:
The arterial blood gas (ABG) values provided are as follows:
- pH: 7.48 (slightly alkaline)
- PaCO2: 38 mmHg (within normal range of 35-45 mmHg)
- HCO3-: 30 mEq/L (elevated, normal range is 22-26 mEq/L)
These ABG results indicate that the patient is experiencing metabolic alkalosis, which is characterized by an elevated pH (greater than 7.45) and an increase in bicarbonate (HCO3-) levels. Let’s break down the values and reasoning:
- pH of 7.48: This value shows that the patient’s blood is more alkaline than normal. The normal range of pH is 7.35 to 7.45. A pH above 7.45 suggests alkalosis, which could be either respiratory or metabolic in origin.
- PaCO2 of 38 mmHg: The partial pressure of carbon dioxide (PaCO2) is within the normal range (35-45 mmHg), which indicates that the respiratory system is not the primary cause of the alkalosis. If respiratory dysfunction were involved, we would expect a deviation in PaCO2. Since the PaCO2 is normal, the respiratory system is likely compensating or unaffected.
- HCO3- of 30 mEq/L: The bicarbonate level is elevated (normal range is 22-26 mEq/L). An increase in bicarbonate is a hallmark of metabolic alkalosis. Bicarbonate is a base, and when its levels are elevated, it leads to an alkalotic state in the blood.
In this case, the imbalance is not due to respiratory dysfunction because the PaCO2 is normal. The primary issue is an increase in HCO3-, which points to a metabolic origin. The kidneys may be retaining bicarbonate, or there may be a loss of acid from the body due to factors such as prolonged vomiting, diuretic use, or excessive intake of alkaline substances like antacids.
Other options explained:
- Metabolic acidosis (Option A) would involve a low pH (below 7.35) and low HCO3-, which does not match the current ABG values.
- Respiratory acidosis (Option C) would show a low pH with elevated PaCO2, indicating hypoventilation, which is not the case here.
- Respiratory alkalosis (Option D) would show an elevated pH but would also have a low PaCO2 (due to hyperventilation), which is not present here.
Thus, the ABG results indicate metabolic alkalosis, and care should be planned accordingly.