A nurse is assessing a preoperative client. The client has a history of atrial fibrillation and is taking warfarin daily. Which test order will the nurse request from the provider?

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.

A. This statement suggests symptoms of vitamin B12 deficiency or glossitis, which are not typical signs of digoxin toxicity. Therefore, it is unlikely to indicate digoxin toxicity.
B. Blurred vision is a common neurological symptom of digoxin toxicity. It occurs due to disturbances in visual acuity and color vision, which can manifest as seeing halos around lights or difficulty focusing. Therefore, this statement is indicative of potential digoxin toxicity.
C. Weight gain can occur due to fluid retention, which is a symptom of heart failure rather than digoxin toxicity. Digoxin toxicity typically presents with neurological and gastrointestinal symptoms rather than weight gain.
D. Constipation is not typically associated with digoxin toxicity. Gastrointestinal symptoms such as nausea, vomiting, and anorexia are more common with digoxin toxicity, but constipation is not a specific indicator.