Progressive Care Nursing Certification (PCCN) Practice Exam

Which laboratory findings support the diagnosis of metabolic alkalosis?

1. pH 7.40, PaCO2 40 mmHg, potassium 4.0 mEq/L

2. pH 7.48, PaCO2 42 mmHg, potassium 3.0 mEq/L

3. pH 7.30, PaCO2 44 mmHg, potassium 3.5 mEq/L

4. pH 7.44, PaCO2 38 mmHg, potassium 6.0 mEq/L

The correct answer is: pH 7.48, PaCO2 42 mmHg, potassium 3.0 mEq/L

The laboratory findings in this scenario indicate a diagnosis of metabolic alkalosis, which is characterized by an increased blood pH, normal or increased PaCO2, and often a decrease in potassium levels. In the context provided, the option with a pH of 7.48 indicates alkalosis, as this value is above the normal range of 7.35-7.45. The PaCO2 of 42 mmHg is relatively normal, which suggests that the respiratory system is compensating adequately without significant respiratory impairment. The potassium level of 3.0 mEq/L is below the normal range (3.5-5.0 mEq/L), which is commonly seen in metabolic alkalosis due to factors such as diuretic use or vomiting leading to potassium loss. Combining these findings, a pH greater than normal, a PaCO2 that does not indicate respiratory acidosis, and a low potassium level point decisively towards a diagnosis of metabolic alkalosis. This understanding is crucial in clinical settings, where recognizing the signs of metabolic imbalances is essential for effective patient management.