Jan 30, 2004

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Pressure Drop: Treating Orthostatic Hypotension

Published on: January 30, 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.

The body then compensates by doing three things. Your heart beats faster. Your brain also tells the blood vessels in the lower half of your body to tighten?about three times as tight as they were before. This pushes blood from the bottom half of your body upwards. It does it all virtually within less than a second.

Now when you're upright you have to maintain the tightness of the blood vessels, otherwise blood will just pool into the lower part of your body. If the amount of pooling is sufficiently great, the blood pressures will fall. And if it falls low enough, you will get symptoms or lose consciousness.

What is orthostatic hypotension?

Normally, when you stand up, your blood pressure actually goes up slightly. Your heart rate usually goes up 5 or 10 beats. So your body really overshoots a little bit to give you a little room to work with.

In people with orthostatic hypotension, upon assuming upright posture, the blood pressure falls more than 20 points systolic or more than 10 points diastolic. What it means is the vessels are not making the initial constriction they should and are allowing too much blood to pool into the lower half of the body.

In some people, this is just a minor thing and they feel a little lightheaded when they get up quickly, but it's no big deal. In other individuals, however, if it's severe, it can make it so that every time they get up, they get a great drop in their blood pressure. And accompanying that, they can have extreme dizziness. They can't think straight due to lack of flow to the brain and may lose consciousness.

Other people may be able to initially make that compensation, but not maintain it. And so as they stand upright for progressively longer periods of time, more and more blood pools into the lower half of their body. This progressive pooling of blood into the lower half of the body, what years ago they were once called "delayed orthostatic hypotension," is not uncommon in older people.

Who is most likely to have this condition?

The orthostatic hypotensive disorders are somewhat more common among older people; older being defined as greater than 50 or 60. When we age, our blood vessels get somewhat hardened and don't respond quickly.

What can cause orthostatic hypotension?

There are a large variety of different conditions that fail to make appropriate compensations for gravity?failure of the adrenal glands, hypothyroidism, dehydration. Sometimes certain medicines will do it. For example, the tricyclic antidepressants are well known for lowering blood pressure.

And interestingly, sometime people have hypertension when they're lying down and hypotension when they're upright. Oftentimes doctors only focus on the hypertensive part of it and give medicines to try and treat it which makes the upright hypotension worse.

And there are some people who develop disorders that result in the inability of their blood vessels to tighten appropriately. Pure autonomic failure, for example, is a disorder that tends to affect older people. Those individuals are unable to control multiple things that the autonomic system controls, not just heart rate and blood pressure. So they may experience not only orthostatic hypotension, but an inability to sweat, difficulty with urination, impotence, rectal dysfunction and a variety of other things.

Many patients with Parkinson's disease will also exhibit orthostatic hypotension that can be severe at times; many of the drugs used to treat Parkinsonism can worsen this.

Another neurodegenerative disorder associated with orthostatic hypotension is Shy-Drager syndrome, which was recently renamed multiple system atrophy. It is characterized by a slow progressive downhill course where people develop not only severe and debilitating orthostatic hypotension and recurrent fainting episodes, but also tremor, difficulty walking, and then a progressive failure of various neurologic functions.

Postural orthostatic tachycardia syndrome, or POTS, is a milder form of failure of the autonomic system where heart rates go very fast on standing. This occurs in an attempt to compensate for an inability to tighten blood vessels and for the higher than normal degree of blood pooling in the lower parts of their body. This disorder tends to affect younger people and occurs more often in females.

How are these conditions diagnosed?

The first thing is accurate measurement of the blood pressure. This has to be done lying down, sitting, immediately upon standing, after two minutes of standing upright and then usually around 5 to 10 minutes of standing. You have to measure the heart rate in all of those positions as well.

In addition, the physician needs to perform a complete physical exam, which includes a neurologic exam to try to rule out other conditions that would cause orthostatic hypotension.

Tilt-table testing is a good diagnostic tool because it's a nice standardized way to measure this. You put somebody on a table and tilt them at a not-upright angle?between 60 and 70 degrees?and you have them strapped into place so they can't fall, but also can't move. A normal individual should be able to stand there for hours. However, in an individual predisposed to these disorders, it will result in a decline in blood pressure.

There are other types of autonomic testing that can be performed if you think there are other aspects of the autonomic system that are failing. For example, you can measure the person's ability to sweat by doing a thing called the thermo-regulatory sweat test.

How is orthostatic hypertension treated?

If you can find and treat a cause such as hypothyroidism or adjust a medication that might be the cause, hypotension can be reversible. Other treatments include Florinef (Fludrocortisone), which raises blood pressure and sensitizes blood vessels so that they can constrict more easily. Vasoconstrictors such as ProAmatine (midodrine) help tighten blood vessels and prevent blood from draining into the lower half of your body. Other drugs used to treat orthostatic hypotension are erythropoietin and yohimbine, which appear to be kinds of vasoconstrictors.

And since vasconstrictors are chemically very similar to stimulant drugs like Ritalin and its cousins, such as Dexedrine, these can also be used. In addition to their stimulant activity in the brain, they constrict blood vessels.

Antidepressant serotonin reuptake inhibitors (SSRIs) are also used because serotonin is the principle neurotransmitter that the brain uses to govern autonomic control, in particular to govern blood pressure.

How else can people with orthostatic hypotension minimize their symptoms?

We've published a series of studies showing that biofeedback can be a very effective therapy in treating these disorders. In biofeedback, the individual tries to learn to control their blood pressure.

There are elastic support hose that, if tight enough, can help prevent pooling into the lower half of the body. They usually have to be waist high because you're pulling blood from your waist down. They are expensive, usually about $100 to $200. They are difficult to put on, hot in the summer, but they are helpful.

People can also drink a large amount of fluid (around two liters) and increase their salt intake to increase the amount of circulating blood and keep their pressure up.

You can also teach people maneuvers to raise their pressures enough to prevent them from passing out. For example, crossing your legs and pushing the legs against each other can sometimes help. When the muscles in your legs contract, they push upon blood vessels and propel blood back to your heart and can raise your blood pressure as much as 10 points.

? 2004 Healthology, Inc.