Which of the following would cause orthostatic hypotension?

Orthostatic hypotension occurs when there is a significant drop in blood pressure when a person moves from a lying or sitting position to a standing position. This can lead to dizziness, lightheadedness, and even fainting. Dehydration is a common cause of orthostatic hypotension because it reduces blood volume. When the body is dehydrated, there is less fluid circulating in the bloodstream, leading to lower overall blood pressure.

As a person stands up, the lack of sufficient blood volume makes it difficult for the body to adequately respond to the change in position, resulting in a drop in blood pressure. Hence, dehydration is directly linked to the physiological mechanisms that underlie orthostatic hypotension, making it the correct choice.

Other factors, such as excess hydration or high sodium intake, typically help maintain or increase blood volume and pressure rather than contribute to hypotension. An elevated heart rate can be a compensatory response to low blood pressure but isn’t typically a direct cause of orthostatic hypotension in itself.