How can we increase preload to increase stroke volume and thus cardiac output in a trauma patient?

• A. IV fluids
• B. Diuretics
• C. Vasopressors
• D. Inotropes (e.g., dobutamine)

Answer: (A)

Preload is the volume of blood in the ventricles at the end of diastole, shaped by venous return to the heart. In a trauma patient who has lost blood, venous return—and thus preload—drops. Giving IV fluids increases intravascular volume, raises venous return, and boosts the end-diastolic volume. This stretch of the heart muscle enhances the force of contraction through the Frank-Starling mechanism, leading to a higher stroke volume and, if the heart remains capable, greater cardiac output.

Diuretics would reduce preload by removing volume. Vasopressors mainly raise arterial tone and blood pressure and can indirectly affect preload, but they don’t directly increase the circulating volume needed to raise preload. Inotropes improve contractility without increasing preload.