Which vital sign is most critical to check before administering digoxin?

Checking the heart rate is crucial before administering digoxin because this medication has a direct effect on the heart. Digoxin is often used to treat conditions such as heart failure and atrial fibrillation, and its therapeutic effects can be influenced by the patient's heart rate.

If the heart rate is too low, particularly if it falls below a certain threshold (often 60 beats per minute), administering digoxin can increase the risk of toxicity and lead to serious complications, such as bradycardia. Therefore, monitoring the heart rate ensures that the medication is given safely and effectively.

In contrast, while blood pressure, temperature, and respirations are important vital signs to monitor in general clinical practice, they are not as directly related to the administration of digoxin. Blood pressure may be affected by other factors, temperature is often unrelated to cardiac function, and respirations can provide insight into overall health but do not specifically indicate whether digoxin can be safely given. Thus, evaluating the heart rate is the most critical step before administering digoxin.