Lyndonville Journal:

Orthostatic Intolerance

David S. Bell, MD

Published in Lyndonville News, May 2000;2(3)

Orthostatic intolerance is a term used for illnesses, which are characterized by inability to maintain the upright posture. It is a group of illnesses that overlaps with CFS just as fibromyalgia does, and it may give up leads as to the underlying pathology of the illness. The most exciting new leads are happening in the world of orthostatic intolerance.

Because much of the literature on OI may be unfamiliar to the reader, I will try to summarize it. For those interested in more in-depth reading, I would start with the February 1999 issue of the American Journal of the Medical Sciences, (Am J Med Sci 1999;317(2). This issue is devoted to a review of OI, and much of what I will say here is taken from that issue. The parallels with CFS are tremendous, starting with the title of the first article by David Robertson, "The epidemic of orthostatic tachycardia and orthostatic intolerance".

Defined simply, OI is the presence of symptoms due to inadequate cerebral perfusion on assuming the upright posture. The usual symptoms include fatigue, nausea, lightheadedness, heart palpitations, sweating, and sometimes passing out. Many persons with medically proven OI have been assumed to have emotional problems when they don't. Like CFS, there have been many terms in the past to describe this group of disorders, including "asthenia" Sound familiar? It is not known what is the exact relationship between OI and CFS, and up until recently studies in the two areas have followed separate tracts. The one very nice advantage OI has over CFS is that it can be proven and there are well defined subgroups.

Over the past year in our office we have been testing patients with CFS for OI by two methods. One has been a circulating blood volume study, described in the last section of this series, and the second is a test for orthostatic intolerance. This test is easily done in the office and requires only a blood pressure cuff and a good nurse to catch the patient before passing out.

The test is relatively simple. The patient lies comfortably for ten minutes and BP and pulse are taken several times. Then the patient stands quietly (no moving around) with the blood pressure cuff on, and BP and pulse are taken every few minutes. This is a poor man's tilt test, and I would argue that it is more accurate because it reproduces exactly what happens to a patient waiting in the check out line at the supermarket.

A person with CFS nearly always has orthostatic intolerance. They describe the symptom of fatigue (which is not fatigue at all) which is characterized by being relatively OK while walking down the aisle of the supermarket, but being unable to stand in the checkout line. The orthostatic testing describes physiologically why this occurs.

There are five separate abnormalities than can occur during quiet standing:

1. Orthostatic systolic hypotension where the upper number (systolic) blood pressure drops. The normal person will not drop BP more than 20 mmHg on standing up. One patient I follow with CFS had a normal BP lying down (100/60) but it fell to 60/0 on standing. No wonder she was unable to stand up - a blood pressure that low is really unable to circulate blood to the brain. In any ICU they would panic seeing a BP like that. And she was turned down for diability because she probably was a hypochondriac.
   
   
2. POTS stands for postural orthostatic tachycardia syndrome. A healthy person will not change their heart rate standing up for an hour. In a person with POTS, the heart rate increases 28 beats per minute (bpm). Some experts say the heart rate should exceed 120 bpm to have POTS. But either way, this increase occurs frequently in CFS. I think the increase in heart rate is linked to the decrease in blood volume. (Orthostatic intolerance has been called Idiopathic hypovolemia in the past)
   
   
3. Orthostatic narrowing of the pulse pressure. The pulse pressure is the difference between the lower number of the BP from the higher number. For example, a normal person with a BP of 100/60 would have a pulse pressure of 40. It is actually the difference between the upper and lower number of the BP that circulates blood. If the pulse pressure drops below 18, it is abnormal and blood would not circulate in the brain well. We routinely see in our patients with CFS blood pressures of 90/80, thus a pulse pressure of 10. The current record holder is a young woman with CFS whose pulse pressure fell to 6 mmHg before she passed out.
   
   
4. Orthostatic diastolic hypertension. The lower number of the BP often reflects the systemic resistance, and while standing many persons with OI and CFS will raise their lower BP number (diastolic) in an attempt to push blood up to the brain. Sometimes this is dramatic. One patient being followed with CFS had a low blood volume, about 60% of normal. While lying down, his BP was 140/80. After standing, his BP rose to 210/140 before we made him lie down. His pulse went up to 140 bpm. He felt rotten but refused to sit down by himself.
   
   As an aside, everyone thought he was a fruitcake - a healthy looking man who said he felt poorly and couldn't work. He was denied disability as usual. Yet when we did the test, he was so determined to stand up I was afraid he was going to stroke out and croak. But he was standing with a BP of 210/140 and a pulse of 140 bpm. He is definitely not a wimp.
   
   After the test, we gave him a liter of saline in the office because he didn't look too good and his blood pressure fell to 90/60 after an hour or so. It is important to note that we had measured his volume the day before so we knew he was hypovolemic. Normally you would never give saline to someone with high blood pressure, it just makes it go higher. In the future, orthostatic testing will require being done in an intensive care unit because these numbers are so scary. Now it is ignored, and patients with CFS called fruitcakes!
   
   
5. Orthostatic diastolic hypotension. This represents a fall in the lower number of the BP, and seems to be the least frequent abnormality in patients with CFS I have tested.

Below is a listing of the abnormalities and the normal values taken from Dr. David Streeten's book Orthostatic Disorders of the Circulation. In the next segment I will describe the results in the first twenty new patients I have tested and how it documents disability. This is important as it will directly measure treatment responses with something other than symptom improvement.

Normal sBP: recumbent: 100-142; Standing (4 min) : 94-141; Orthostatic change: -19 to +11
Normal dBP: recumbent: 55-90; Standing : 61-97; Orthostatic change: -9 to +22
Normal P: recumbent: 54-96; Standing: 62-108; Orthostatic change: -6 to +27

Orthostatic systolic hypotension: fall in systolic blood pressure of 20 mmHg or more
Orthostatic diastolic hypotension: fall in diastolic BP of 10 mm Hg or more.
Orthostatic diastolic hypertension: rise in diastolic BP to 98 mm Hg or higher
Orthostatic narrowing of pulse pressure: fall in pulse pressure to 18 mm Hg or lower.
Orthostatic postural tachycardia: increase in heart rate of 28 bpm or to greater than 110 b/min.

Reference: Streeten DHP. Orthostatic disorders of the circulation. New York: Plenum, 1987:116.

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