A 72-year-old man is brought to the emergency department with waxing and waning chest pressure over the past several hours. The patient says he occasionally gets a similar sensation that lasts 5-10 minutes when he walks briskly up the stairs. Medical history is significant for hypertension and hyperlipidemia; he has been nonadherent with prescribed medical therapy and follow-up visits. The patient has a 25-pack-year smoking history. Blood pressure is 211/105 mm Hg, and pulse is 88/min and regular. Chest examination reveals no heart murmurs, and the lungs are clear. ECG shows sinus rhythm and nonspecific ST-segment changes. A medication is administered intravenously and produces the following hemodynamic effects compared to baseline: Which of the following medications was most likely used in this patient?

Question

A 72-year-old man is brought to the emergency department with waxing and waning chest pressure over the past several hours.  The patient says he occasionally gets a similar sensation that lasts 5-10 minutes when he walks briskly up the stairs.  Medical history is significant for hypertension and hyperlipidemia; he has been nonadherent with prescribed medical therapy and follow-up visits.  The patient has a 25-pack-year smoking history.  Blood pressure is 211/105 mm Hg, and pulse is 88/min and regular.  Chest examination reveals no heart murmurs, and the lungs are clear.  ECG shows sinus rhythm and nonspecific ST-segment changes.  A medication is administered intravenously and produces the following hemodynamic effects compared to baseline:  Which of the following medications was most likely used in this patient?

Quizplus · Accepted Answer

Systolic blood pressure ≥180 mm Hg (or diastolic pressure ≥120 mm Hg) along with evidence of associated end-organ damage (eg, chest pressure, ST-segment changes on ECG) constitutes a hypertensive emergency. This patient likely has underlying coronary artery disease and is experiencing myocardial ischemia due to increased myocardial oxygen demand caused by markedly elevated blood pressure and increased left ventricular afterload. Management of hypertensive emergency involves prompt and controlled blood pressure reduction to reduce the risk of complications (eg, stroke, aortic dissection, myocardial infarction). Labetalol is a nonselective vasodilatory beta blocker that blocks beta-1, beta-2, and alpha-1 adrenergic receptors and reduces blood pressure. The alpha-1 receptor blockade outweighs beta-2 receptor blockade in vascular smooth muscle to cause peripheral vasodilation of both venules and arterioles. Venular vasodilation decreases venous return and arteriolar vasodilation decreases systemic vascular resistance (SVR); because the vasodilation is relatively balanced, blood pressure is reduced with stroke volume unchanged. Normally, reduced blood pressure stimulates a baroreceptor reflex-mediated increase in heart rate, but the strong beta-1 receptor blockade of labetalol overrides this response, causing overall decreased heart rate. (Choices A, D, and E) Hydralazine is an arterial vasodilator that has little effect on veins. Nitroprusside is a nitric oxide donor that causes balanced arterial and venous vasodilation. Phentolamine is a nonselective alpha receptor blocker that also causes balanced vasodilation. All these drugs reduce blood pressure primarily via a reduction in SVR, but they have no negative chronotropic effects and are associated with a baroreceptor reflex-mediated increase in heart rate. Stroke volume is increased with hydralazine, and unchanged with the balanced vasodilation that occurs with nitroprusside and phentolamine. (Choice C) Metoprolol is a cardioselective beta blocker that primarily blocks beta-1 receptors; it causes slight blockade of beta-2 receptors and has no effect on alpha receptors. Metoprolol causes no significant change in SVR but facilitates a mild reduction in blood pressure due to a decrease in contractility and heart rate that reduces stroke volume and cardiac output. Educational objective: Labetalol is a nonselective vasodilatory beta blocker that blocks beta-1, beta-2, and alpha-1 adrenergic receptors. Alpha-1 receptor blockade outweighs beta-2 receptor blockade to cause peripheral vasodilation with decreased venous return and lower systemic vascular resistance. The relatively balanced vasodilation reduces blood pressure without changing stroke volume. Beta-1 receptor blockade overrides the expected baroreflex-mediated increase in heart rate, resulting in overall decreased heart rate.

A 72-Year-Old Man Is Brought to the Emergency Department with Waxing