Final answer:
The vital sign of greatest concern to the nurse prior to administering digoxin (Lanoxin) is heart rate.
Step-by-step explanation:
The vital sign of greatest concern to the nurse prior to administering digoxin (Lanoxin) would be heart rate. Digoxin is a medication used to treat heart conditions such as congestive heart failure and atrial fibrillation. It works by slowing down the heart rate and strengthening the heart's contractions.