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Orthostatic hypotension
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Orthostatic hypotension, also called postural hypotension, is a sudden drop in blood pressure right when a person stands up after sitting or lying down. The word orthostatic means exactly that: standing upright.
When you stand, gravity pulls blood downward and some of it pools in the legs, like water sinking to the bottom of a bag when you lift it. As a result, less blood returns to the heart through the veins, which is called venous return, and the heart has less blood to pump out: cardiac output falls. Normally the body makes up for this. Sympathetic tone, an automatic signal from the nervous system, rises, and that signal constricts the arterioles, the small vessels that distribute blood. This response is called the baroreceptor reflex.
When that compensation doesn't happen, symptoms appear, and they often come from less blood reaching the brain. But symptoms aren't always present: some people with orthostatic hypotension feel nothing at all.
In brief
Orthostatic, or postural, hypotension is a sudden drop in blood pressure on standing up after sitting or lying down.
On standing, gravity pools blood in the legs, and venous return and cardiac output fall; normally the body compensates by raising sympathetic tone, which constricts the arterioles: this is the baroreceptor reflex.
Like water sinking to the bottom of a bag when you lift it.
If that compensation fails to occur, symptoms appear, often from reduced blood flow to the brain, although some people have none.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingOrthostatic Hypotension, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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