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Hypertension Hypertension Basics

Pressure Drop: Treating Orthostatic Hypotension


Medically Reviewed On: September 15, 2004

By Christine Haran

In a society that breeds tightly wound, type-A personalities, it's no surprise that hypertension, or high blood pressure, is a major health concern. But low blood pressure can also wreak havoc on one's health and ability to function. Blood pressure can bottom out for a variety of reasons, including massive blood loss, certain heart disorders, severe infection and from some drugs. And a low blood pressure condition known as orthostatic hypotension, which affects many older people—and some younger ones—often goes undiagnosed and untreated.

When most people stand up, their blood pressure rises to increase blood flow to the brain. But people with orthostatic hypotension experience a decline in blood pressure when they stand, or after periods of standing or walking. As a result, they feel dizzy and sometimes faint, and often risk hurting themselves during falls.

Below, Blair P. Grubb, MD, a professor of medicine and pediatrics at the Medical College of Ohio in Toledo, explains what causes hypotension and how people can learn to live with it.

Can someone's blood pressure be too low?
Just as there are some individuals whose blood pressures seem to run too high, there are also individuals in whom blood pressures seem to run too low. Blood pressure has to be adequate to provide enough blood and therefore oxygen to reach the brain. Once it drops below a certain threshold, there is not enough blood going to the brain and you can experience a whole bunch of different symptoms. Depending upon how much the oxygen delivery to the brain drops, there can be fatigue, light-headedness, problems thinking and ultimately loss of consciousness.

How is blood pressure controlled during standing?
The system that regulates all this activity is referred to as the autonomic nervous system. When normal individuals stand, gravity tries to pull blood downward into the lower half of the body. By being on two legs, humans have the greatest degree of challenge because our blood pressure regulating systems were mainly designed for an animal that would be on all-fours. So that the very organ that defines our humanity, our brain, is placed really at a very precarious position in reference to maintaining a constant oxygen supply to it.

So when a normal person stands up, gravity will try to pull somewhere between a quarter and a third of your blood into the lower part of your body. Your brain senses that this has happened when receptors in blood vessels are stretched giving off more electrical activity. So when you stand what your brain detects is a sudden increase in the electrical activity coming from the lower half of the body's blood vessels compared to the upper half of the body's blood vessels.

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