A nurse is planning to administer digoxin to a client who has heart failure. Which of the following laboratory results is the priority for the nurse to review prior to administering the medication?

A. Potassium levels are important for assessing electrolyte balance and are not directly indicative of protein intake or synthesis.
B. Calcium levels are important for bone health, nerve function, and muscle contraction. They are not directly indicative of protein intake or synthesis.
C. Albumin is a plasma protein that reflects the body's nutritional status and liver function. It has a relatively long half-life (approximately 20 days), making it a useful marker for assessing protein intake and synthesis over time. Low albumin levels can indicate malnutrition, liver disease, or other conditions affecting protein metabolism.
D. Sodium levels are important for fluid balance and nerve function. They are not directly indicative of protein intake or synthesis.

A. Hemoglobin levels are important for assessing oxygen-carrying capacity of the blood. While anemia can affect tissue oxygenation and exacerbate symptoms in heart failure, it is not directly related to the risk of digoxin toxicity.
B. Creatinine levels are used to assess kidney function. Impaired kidney function can affect the clearance of digoxin from the body, potentially increasing the risk of toxicity. However, potassium levels have a more direct impact on the risk of digoxin toxicity.
C. BUN levels are also used to assess kidney function. Similar to creatinine, impaired kidney function can affect digoxin clearance, but potassium levels are more directly related to the risk of digoxin toxicity.
D. Potassium levels are critical because hypokalemia (low potassium) can predispose the client to digoxin toxicity. Digoxin competes with potassium for binding sites on the sodium-potassium ATPase pump in cardiac cells. When potassium levels are low, digoxin can bind more readily to these pumps, leading to increased toxicity and potentially life-threatening arrhythmias such as ventricular tachycardia or ventricular fibrillation.