Final answer:
The nurse should monitor the serum potassium level when considering cardiac problems and digoxin toxicity, as digoxin can cause hyperkalemia. The correct answer is option c.
Step-by-step explanation:
The laboratory test that the nurse should monitor for potential cardiac problems and digoxin toxicity is c. Serum potassium level. Digoxin is a medication used to treat various heart conditions, such as atrial fibrillation, atrial flutter, and sometimes heart failure.
It does so by increasing the contractility of the heart muscles. However, its therapeutic index is narrow, meaning that there is a fine line between the effective and toxic doses of digoxin. Digoxin toxicity is closely related to potassium levels because digoxin can cause hyperkalemia, which can lead to cardiac problems.
A serum potassium level test is thus essential in monitoring patients on digoxin to ensure that their potassium levels remain within the normal range and to prevent toxicity. Other tests, such as the complete blood count, BUN and creatinine levels, and PT/INR, are significant but do not directly monitor for digoxin toxicity.