Final answer:
The correct action for the nurse is to withhold the client's metoprolol medication due to the risk of worsening bradycardia, given the current heart rate of 48/min.
Step-by-step explanation:
A nurse is planning to administer metoprolol to a client who has heart failure and a heart rate of 48/min. Norepinephrine (NE) binds to the beta-1 receptor. Beta blockers, such as metoprolol, work by blocking these receptors, thus can lower the heart rate (HR). Since the patient's current HR is below normal range, administration of a beta blocker could potentially worsen bradycardia (a slower than normal heart rate) or lead to cardiac arrest.
Given this information, the correct action for the nurse would be D) Withhold the client's medication and report the low heart rate to the healthcare provider for further assessment and instructions. Administering the medication could be dangerous and contrary to the therapeutic intent, which is to manage heart failure without causing bradycardia.