In the treatment of pulmonary edema with a loop diuretic, which statement best describes its action?

• A. It causes vasoconstriction to decrease venous capacitance and improve preload.
• B. It decreases water retention by the kidneys to reduce edema.
• C. It increases water retention by the adrenal glands to improve circulation.
• D. It causes vasodilation to increase venous capacitance and decrease preload.

Answer: (D)

Loop diuretics relieve pulmonary edema by rapidly lowering the pressures that drive fluid into the lungs. They do this first through venodilation, which increases venous capacitance and reduces preload (the amount of blood returning to the heart). This immediate drop in filling pressures lessens pulmonary congestion. The diuretic effect, which promotes kidney excretion of salt and water, provides longer‑term volume reduction, but the quickest and most impactful change in pulmonary edema is the venodilation and decreased preload. So describing its action as causing vasodilation to increase venous capacitance and decrease preload best captures the key mechanism at work.