postural hypotension is a common cause of an episode of temporary loss of consciousness or feelings of lightheadedness. postural hypotension results from changing body position from a prone supine or sitting position to a more vertical position. normally blood tends to pool in the legs due to gravity when a person stands up potentially reducing the amount of blood available to return to the heart. nerves to the blood vessels in the legs normally act to compensate for this pooling by constricting thus sending blood away from the leg veins and toward the heart. however poor tone of the nerves to blood vessels in the legs can cause this mechanism to fail resulting in a disproportionate distribution of blood to the legs instead of returning to the circulation so the brain receives less oxygen. as a result a person feels lightheaded and may even faint.
what is postural hypotension (orthostatic hypotension)?