A 64-year-old man with a long history of hypertension arrives at the emergency department complaining of a dry cough and shortness of breath. For the past two days, the patient has been unable to sleep in a flat position. The blood pressure is 192/102 mm Hg, and the pulse rate is 92 beats per minute. An S4 and bibasilar crackles are discovered during a physical examination. He begins receiving intravenous nitroglycerin infusions and soon reports significant symptom relief. Which of the following physiologic changes are most likely to occur following administration of this medication?

Question

Quizplus · Accepted Answer

Eductional Objective: The clinical presentation of this patient is consistent with acute pulmonary edema caused by severely elevated blood pressure (hypertensive emergency). Intravenous vasodilators (such as nitroglycerine and sodium nitroprusside) are frequently used to treat acute heart failure caused by severe hypertension.
Nitrates are primarily venodilators, increasing peripheral venous capacitance and thus lowering cardiac preload, left ventricular end-diastolic pressure (LVEDP), and volume. In patients with acute pulmonary edema, this is the primary mechanism of action for symptom relief. Lowering LVEDP also reduces LV systolic wall stress and myocardial oxygen demand, resulting in relief of angina symptoms. Although nitrates' vasodilatory effects primarily affect the venous system, they also have a minor effect on arteriolar dilation. Higher doses can lead to a significant drop in systemic blood pressure, thereby decreasing cardiac afterload, reducing left ventricle wall stress, and causing a further decrease in myocardial oxygen demand.

A 64-Year-Old Man with a Long History of Hypertension Arrives