Which statement best describes the hemodynamic change causing orthostatic hypotension after prolonged bed rest?

Which statement best describes the hemodynamic change causing orthostatic hypotension after prolonged bed rest?

• A. Increased arterial pressure
• B. Decreased venous return to the heart
• C. Increased venous tone in the legs
• D. Increased heart rate due to parasympathetic activity

Answer: (B)

When you stand after being in bed for a long time, gravity pulls more blood into the veins of the legs and abdomen. To keep blood pressure stable, the body relies on venous tone and the muscle pump to push blood back to the heart (increasing venous return). Prolonged bed rest makes the venous system more compliant and can lower circulating volume, so blood pools more in the lower limbs when standing. This reduces the preload on the heart, lowers stroke volume and cardiac output, and causes blood pressure to drop—orthostatic hypotension. The other statements don’t fit because increasing arterial pressure would oppose the hypotension; increasing venous tone in the legs would reduce pooling and help maintain return to the heart; and an increase in heart rate due to parasympathetic activity would not cause the observed drop in blood pressure (parasympathetic activity slows heart rate, whereas orthostatic symptoms are more about inadequate venous return and reflex sympathetic responses).

When you stand after being in bed for a long time, gravity pulls more blood into the veins of the legs and abdomen. To keep blood pressure stable, the body relies on venous tone and the muscle pump to push blood back to the heart (increasing venous return). Prolonged bed rest makes the venous system more compliant and can lower circulating volume, so blood pools more in the lower limbs when standing. This reduces the preload on the heart, lowers stroke volume and cardiac output, and causes blood pressure to drop—orthostatic hypotension.

The other statements don’t fit because increasing arterial pressure would oppose the hypotension; increasing venous tone in the legs would reduce pooling and help maintain return to the heart; and an increase in heart rate due to parasympathetic activity would not cause the observed drop in blood pressure (parasympathetic activity slows heart rate, whereas orthostatic symptoms are more about inadequate venous return and reflex sympathetic responses).