A patient is ordered to receive digoxin to treat congestive heart failure. The nurse is most concerned about which assessment finding.

A) RR 18 bpm:
A respiratory rate of 18 breaths per minute is within the normal range for adults (12-20 bpm). Therefore, this finding does not pose a significant concern in the context of digoxin therapy. Respiratory rate should be monitored, especially if the patient is experiencing signs of heart failure or digoxin toxicity, but 18 bpm alone is not alarming.

B) 1+ pitting edema of the lower extremities:
Pitting edema, especially with a grade of 1+ (slight indentation), is a common finding in patients with congestive heart failure (CHF). It indicates fluid retention due to the heart's inability to pump blood effectively. While edema should be monitored, it is not immediately life-threatening or specific to digoxin toxicity.

C) BP 138/90 mm Hg:
A blood pressure of 138/90 mm Hg is slightly elevated, but it is not excessively high. This finding is manageable and should be monitored, particularly in heart failure patients, but it does not present an immediate concern in this case. Blood pressure management is crucial in CHF, but it does not directly correlate with digoxin toxicity.

D) Heart rate 54 beats/min:
A heart rate of 54 beats per minute is considered bradycardic, especially in a patient taking digoxin. Digoxin can lower heart rate by increasing vagal tone and inhibiting the AV node. Bradycardia is a well-known sign of digoxin toxicity, and this finding is concerning because it may indicate that the patient is experiencing toxicity. Digoxin-induced bradycardia can lead to more serious arrhythmias or hemodynamic instability, making this the most concerning finding that requires immediate assessment and possibly intervention.