Which hemodynamic parameter is most directly reduced by diuretic therapy such as Lasix?

Which hemodynamic parameter is most directly reduced by diuretic therapy such as Lasix?

• A. Contractility
• B. Afterload
• C. Heart Rate
• D. Preload

Answer: (D)

The key idea is how diuretics change the heart’s filling pressure. Loop diuretics like Lasix promote Na+ and water loss, which lowers circulating blood volume. With less volume returning to the heart, the filling pressures fall, reducing end-diastolic volume and the stretch of the ventricles at the end of diastole. That decrease in ventricular filling pressure—the preload—is the direct, primary effect of this kind of therapy. Contractility and heart muscle strength aren’t directly changed by diuretics; they act on the volume status rather than the strength of contraction. Afterload, or the resistance the heart pumps against, isn’t the primary target of diuretics either—though blood pressure can change indirectly with volume status, the main action is to decrease preload. Heart rate isn’t directly controlled by diuretics either, so it’s not the primary effect. So, preload is the hemodynamic parameter most directly reduced by Lasix, aligning with how these drugs relieve venous congestion by lowering filling pressures.

The key idea is how diuretics change the heart’s filling pressure. Loop diuretics like Lasix promote Na+ and water loss, which lowers circulating blood volume. With less volume returning to the heart, the filling pressures fall, reducing end-diastolic volume and the stretch of the ventricles at the end of diastole. That decrease in ventricular filling pressure—the preload—is the direct, primary effect of this kind of therapy.

Contractility and heart muscle strength aren’t directly changed by diuretics; they act on the volume status rather than the strength of contraction. Afterload, or the resistance the heart pumps against, isn’t the primary target of diuretics either—though blood pressure can change indirectly with volume status, the main action is to decrease preload. Heart rate isn’t directly controlled by diuretics either, so it’s not the primary effect.

So, preload is the hemodynamic parameter most directly reduced by Lasix, aligning with how these drugs relieve venous congestion by lowering filling pressures.