Interpreting Laboratory Values in Heart Failure

A nurse is reviewing the laboratory values for a 74-year-old female patient who has been diagnosed with congestive heart failure (CHF) and controlled hypertension. The patient is currently prescribed diuretics and ACE inhibitors. Recent blood tests show the following laboratory values:

• Serum potassium: 5.8 mEq/L
• Serum creatinine: 1.2 mg/dL
• Serum sodium: 138 mEq/L
• Blood urea nitrogen (BUN): 20 mg/dL

The nurse must interpret these values in the context of the medications and the patient's condition. Which laboratory value should the nurse identify as potentially indicating a risk for the patient?