Acute expansion of blood volume will cause which of the following?

Acute expansion of blood volume will cause which of the following?

• A. Raise arterial blood pressure
• B. Decrease arterial blood pressure
• C. Cause peripheral vasoconstriction and increased heart rate
• D. No effect on arterial pressure

Answer: (A)

Increasing blood volume acutely boosts venous return to the heart, raising preload. The heart responds to this greater stretch by contracting more forcefully, so stroke volume goes up (the Frank-Starling mechanism). With more blood being ejected each beat, cardiac output rises, which raises arterial (mean) pressure, even before reflexes adjust. So the immediate effect of an acute volume expansion is an increase in arterial blood pressure. The other options describe responses more typical of volume loss or no change and don’t fit the immediate consequence of suddenly more circulating volume.

Increasing blood volume acutely boosts venous return to the heart, raising preload. The heart responds to this greater stretch by contracting more forcefully, so stroke volume goes up (the Frank-Starling mechanism). With more blood being ejected each beat, cardiac output rises, which raises arterial (mean) pressure, even before reflexes adjust. So the immediate effect of an acute volume expansion is an increase in arterial blood pressure. The other options describe responses more typical of volume loss or no change and don’t fit the immediate consequence of suddenly more circulating volume.