What vital sign is essential to monitor before administering beta-blockers?

Monitoring heart rate before administering beta-blockers is essential because these medications primarily function by blocking the effects of adrenaline on beta-adrenergic receptors. This action leads to a decrease in heart rate and myocardial contractility, reducing the workload on the heart.

A significantly low heart rate, known as bradycardia, can be exacerbated by beta-blockers, potentially leading to adverse effects. Therefore, assessing the patient's baseline heart rate helps ensure that it is at an acceptable level before administration. If the heart rate is too low, the healthcare provider may need to reconsider the use of the beta-blocker or adjust the dosage accordingly.

Blood pressure is also important to monitor, as beta-blockers can affect it, but the priority lies in ensuring that heart rate is within a safe range to avoid complications such as severe bradycardia or potential cardiac arrest. Monitoring temperature and respiratory rate, while essential for overall patient assessment, are not directly impacted by beta-blocker therapy in the same immediate and significant manner as heart rate.