During general anesthesia, which agent should be administered with caution to a patient on high dose propranolol?

When considering the administration of agents during general anesthesia, particularly in a patient on high-dose propranolol, phenylephrine is an important choice to evaluate closely. Propranolol is a non-selective beta-blocker that decreases heart rate and myocardial contractility. It also blocks the effects of catecholamines, which can alter cardiovascular dynamics.

Phenylephrine is a potent alpha-1 adrenergic agonist that is commonly used as a vasopressor to increase blood pressure and manage hypotension. While it can be effective in these situations, it has the potential to cause reflex bradycardia due to its strong vasoconstrictive effects, which might be exacerbated by the actions of propranolol. The combination can lead to an increased risk of bradycardia and other cardiovascular complications.

Therefore, when administering phenylephrine to a patient taking high doses of propranolol, careful monitoring is essential, and it may need to be used with caution due to potential adverse interactions and the impact on the patient's heart rate and blood pressure management.

The other agents listed, while they may require monitoring as well, do not pose the same level of concern regarding reflex bradycardia or interaction due to the mechanisms of propranol