A patient presents with suspected dissecting aneurysm; which IV agent is used to rapidly decrease heart rate?

• A. Atropine
• B. Phenylephrine
• C. Ketamine
• D. Esmolol

Answer: (D)

In suspected aortic dissection, the immediate goal is to quickly reduce the forces driving blood through the true and false channels—the heart rate and the force of pressure entering the aorta. An IV beta-blocker that works rapidly and can be finely titrated fits this need, and esmolol is ideal because it is ultra-short-acting and primarily blocks beta-1 receptors in the heart. By lowering heart rate and contractility, esmolol reduces the rate of rise of aortic pressure (dP/dt) and the wall shear stress on the dissected aorta. Its short half-life means clinicians can quickly adjust or stop the medication if blood pressure falls too low, which is a crucial safety feature in this scenario. Targeting a slower heart rate, around 60 beats per minute, with a systolic blood pressure of roughly 100–120 mmHg helps prevent extension of the dissection and potential rupture. The other options would worsen the situation: atropine would raise heart rate, phenylephrine increases afterload and BP, and ketamine can elevate blood pressure and sympathetic tone, all undesirable in a suspected dissection. After heart rate control is achieved, additional vasodilators can be added to further reduce BP as needed.