What diagnostic test should the nurse check for a client with new onset atrial fibrillation after a coronary artery bypass graft?

In cases of new onset atrial fibrillation, particularly following a coronary artery bypass graft, monitoring the serum potassium level is crucial. Electrolyte imbalances, especially hypokalemia (low potassium levels), can provoke or exacerbate arrhythmias, including atrial fibrillation. Potassium plays an essential role in maintaining normal electrical activity of the heart; therefore, ensuring that potassium levels are within the normal range helps to stabilize cardiac electrical conduction and reduce the risk of further arrhythmias.

While arterial oxygen levels could provide valuable information about the patient’s respiratory status, they are not directly linked to the etiology of atrial fibrillation. Similarly, serum sodium and blood urea nitrogen levels, although important indicators of metabolic and renal function, are less directly related to the development of arrhythmias. Focusing on serum potassium allows for the identification and correction of an electrolyte disturbance that could be contributing to the patient's atrial fibrillation following surgery.