During surgery, which drug should be avoided in patients with significant aortic stenosis?

In patients with significant aortic stenosis, it is crucial to maintain adequate cardiac output and avoid medications that can lead to decreased heart rate or reduced cardiovascular output. Phenylephrine is a potent vasoconstrictor that can increase systemic vascular resistance, potentially leading to a decrease in stroke volume and cardiac output. In the context of aortic stenosis, where the left ventricle is already facing obstruction to blood flow during systole, using a vasopressor like phenylephrine can exacerbate hemodynamic instability and worsen the patient's condition.

On the other hand, drugs like ephedrine may be more suitable in some cases as it has both vasoconstrictive and positive inotropic effects. Atenolol, a beta-blocker, can be problematic but is not necessarily contraindicated in all scenarios. Atropine, an anticholinergic, can increase heart rate and may be beneficial in bradycardic situations. Therefore, avoiding phenylephrine in this specific scenario is vital due to its adverse effects on hemodynamics in patients with significant aortic stenosis.