Hypotension
is often sub divided into different categories; postural or orthostatic
hypotension, Shy-Drager syndrome and neurally mediated hypotension.
Orthostatic hypotension | postural hypotension
Postural or
orthostatic hypotension is a sudden drop in blood pressure,
when one stand up from a sitting position or if one stand up after
lying down. Ordinarily, blood pools in the legs whenever one stands,
but the body compensates for this by increasing the heart rate and
constricting blood vessels, thereby ensuring that enough blood returns
to the brain. But in people with postural hypotension, this
compensating mechanism fails and blood pressure falls, leading to
dizziness, lightheadedness, blurred vision and even fainting.
Causes
of orthostatic hypotension
Postural hypotension can occur for a variety of reasons including
dehydration, prolonged bed rest, pregnancy, diabetes, heart problems,
burns, excessive heat, large varicose veins and certain neurological
disorders. A number of medications can also cause postural hypotension,
particularly drugs used to treat high blood pressure, as well as
antidepressants and drugs used to treat Parkinson's disease and
erectile dysfunction.
Facts
about orthostatic hypotension
Postural hypotension is especially common in older adults, with as many
as 20 percent of those over age 65 experiencing postural hypotension.
But postural hypotension can also affect young, otherwise healthy
people who stand up suddenly after sitting with their legs crossed for
long periods or after working for a time in a squatting position.
Shy-Drager syndrome - hypotension
Low blood pressure due to nervous system damage, called as
Shy-Drager
syndrome, this rare disorder causes progressive damage to the autonomic
nervous system, which controls involuntary functions such as blood
pressure, heart rate, breathing and digestion. Although multiple system
atrophy can be associated with muscle tremors, slowed movement,
problems with coordination and speech, and incontinence, its main
characteristic is severe orthostatic hypotension in combination with
very high blood pressure when lying down. Multiple system atrophy can't
be cured and usually proves fatal within seven to 10 years of diagnosis.
Postprandial hypotension
Low blood pressure after eating is called as postprandial hypotension,
a problem that almost exclusively affects older adults. Just as gravity
pulls blood to the feet when stand, a large amount of blood flows to
the digestive tract after eating. Ordinarily, the body counteracts this
by increasing the heart rate and constricting certain blood vessels to
help maintain normal blood pressure. But in some people these
mechanisms fail, leading to dizziness, faintness and falls.
Postprandial hypotension is more likely to affect people with high
blood pressure or autonomic nervous system disorders such as
Parkinson's disease. Lowering the dose of blood pressure drugs and
eating small, low-carbohydrate meals may help reduce symptoms.
Neurally mediated hypotension
Low blood pressure from faulty brain signals is called as neurally
mediated hypotension. Unlike orthostatic hypotension, which occurs when
you stand up from a sitting or lying position, this disorder causes
blood pressure to drop after standing for long periods, leading to
symptoms such as dizziness, nausea and fainting. It seems to occur
because of a miscommunication between the heart and the brain. When one
stand for extended periods, the blood pressure falls as blood pools in
to the legs. Normally, the body then makes adjustments to normalize the
blood pressure. But in people with neurally mediated hypotension,
nerves in the heart's left ventricle actually signal the brain that
blood pressure is too high, rather than too low, and so the brain
lessens the heart rate, decreasing blood pressure even further. This
causes more blood to pool in the legs and less blood to reach the
brain, leading to lightheadedness and fainting.
