Q:
What is neurally mediated hypotension??
A: Neurally mediated hypotension
(NMH)
is a condition in which the body has difficulty regulating the blood
pressure, especially when one is upright. There seems to be a
misconnection between the brain and the nerves that control the blood
pressure and heart rate. The reason is unknown.
Q: What
happens in this condition?
A: People with this condition
experience spells in which the blood pressure drops suddenly, leading to
weakness, lightheadedness or dizziness, sweating, vision disturbance and a
feeling of fainting or near-fainting. During an episode, some people may
get an irresisible urge to sit or lie down or a feeling that something bad
may happen if they remain standing.
Q: What is
the result of such a spell of low blood pressure??
A: A person suffering spells like this
may have prolonged fatigue, weakness, and difficulty with thought,
concentration and memory.
Q: Do only
people with CFS get NMH??
A: No. It may be seen in people who
have no fatigue. And NMH is not seen in all CFS cases, either.
Q: What
exactly happens in a spell of NMH??
A: It's a complicated set of events,
but basically here's what happens: First, the blood pressure starts to
fall. Normally, that would cause the heart to speed up and the blood
vessels in the legs to tighten (constrict), leading to a rise in the blood
pressure. In people suffering NMH, the fall in the blood pressure causes
the heart to slow down and the blood vessels in the legs to loosen
(dilate). The result is a much greater fall in the blood pressure. The
blood flow to the brain then is sharply reduced and fainting or
near-fainting results.
Q: Why do the
heart and blood vessels respond improperly??
A: The cause is not currently known.
Q: Is NMH the
cause of CFS??
A: Some researchers have claimed that
CFS is caused by NMH. However, many physicians who specialize in the
treatment of CFS believe that this blood pressure regulation is simply
another body system knocked out of kilter by CFS. Although it appears that
many CFS patients have NMH, clearly there are many others that do not.
More research is needed to clear up this point.
Q: How is NMH
diagnosed??
A: Unfortunately, it cannot be
diagnosed with simple blood pressure measurements. This condition is
not the same as the common momentary dizziness that even many well
people get when they arise from a chair or from a bed too quickly. The
diagnosis requires a "tilt table test".
Q: What is a
tilt table test??
A: Under the supervision of a
physician, the patient rests motionlessly on a special table that slow
tilts upward to a near-standing position. The patient then remains
standing on a footrest with a safety belt in place. Blood pressure and
pulse rates are continually monitored by a machine. A positive test occurs
if the blood pressure falls along with a sudden drop in the pulse rate.
If this blood pressure does not fall during this phase of the test, a medication to raise the pulse rate is given intravenoulsy. If the blood pressure and the pulse rate fall during this stage of the test, then the test is considered positive as well.
Q: How is NMH
treated??
A: Treatment consists of medication
that prevents the heartbeat from slowing when it should be speeding up,
medication to boost the blood pressure and sometimes a change in the diet
to include more sodium (salt). Treatment must be individualized for
each patient; there is no standard "one size fits all" dose.
Q: Is
treatment always effective??
A: Unfortunately, no. Quite a few
patients will feel better overall and some will feel great. In perhaps a
third of the patients with this condition, treatment doesn't seem to help
at all. Side effects are often a problem to CFS patients (who are
ordinarily more sensitive to medications).
Q: Should I
just start on a high-salt diet??
A: No. High-salt diets may not be
helpful and even *dangerous* for some patients. Proper diagnosis is
necessary before such diet modifications are made.
Q: Should
every CFS patient get a tilt table test now??
A: No. The research that has been
published is limited and we can't draw too many conclusions from it. We
are not recommending the test for every CFS patient. We are trying to
screen patients based on their medical history and their answers to
certain questions. At some point in the future, the tilt table test may
possibly become a standard test for CFS but currently it is considered a
"special circumstances" test.
Q: Is there
any special preparation for a tilt table test??
A: Certain medications may affect the
results and should be discontinued under the physicians supervision one to
two days before the test. These medications include amitriptyline and
other tricyclic antidepressants, beta-blockers, and certain muscle
relaxants.
© 1996, Inter I.D., Tulsa, OK
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