What effect does a diuretic have on preload?

What effect does a diuretic have on preload?

• A. Increases preload
• B. Increases afterload
• C. Decreases preload
• D. Decreases afterload

Answer: (C)

Preload is the filling pressure of the ventricle at the end of diastole, driven by venous return and circulating volume. A diuretic increases urine production, reducing plasma volume and overall circulating blood volume. With less volume returning to the heart, venous return falls, end-diastolic volume and pressure drop, so preload decreases. This helps lessen ventricular stretch and fluid overload. Afterload is the resistance the heart must pump against; diuretics don’t directly lower this resistance, so they primarily reduce preload rather than afterload.

Preload is the filling pressure of the ventricle at the end of diastole, driven by venous return and circulating volume. A diuretic increases urine production, reducing plasma volume and overall circulating blood volume. With less volume returning to the heart, venous return falls, end-diastolic volume and pressure drop, so preload decreases. This helps lessen ventricular stretch and fluid overload. Afterload is the resistance the heart must pump against; diuretics don’t directly lower this resistance, so they primarily reduce preload rather than afterload.