Definition of Fainting (syncope)
Fainting (syncope): Partial or complete loss of
consciousness with interruption of awareness of oneself and ones
surroundings. When the loss of consciousness is temporary and there
is spontaneous recovery, it is referred to as syncope or, in
nonmedical quarters, fainting. Syncope accounts for one in every 30
visits to an emergency room. It is pronounced sin-ko-pea.
Syncope is due to a temporary reduction in blood flow and
therefore a shortage of oxygen to the brain. This leads to
lightheadedness or a "black out" episode, a loss of consciousness.
Temporary impairment of the blood supply to the brain can be caused
by heart conditions and by conditions that do not directly involve
the heart:
Non-cardiac causes: Syncope is most commonly caused
by conditions that do not directly involve the heart. These
conditions include:
- Postural orthostatic hypotension: Drop in blood pressure due to
changing body
position to a more vertical position after lying or sitting;
- Dehydration causing a decrease in blood volume.
- Blood pressure medications leading to low blood pressure.
- Diseases of the nerves to the legs in older people (especially
with diabetes or Parkinson's disease) when poor tone of the nerves of
the legs draws blood into the legs from the brain.
- High altitude.
- Brain stroke or "near-stroke" (transient ischemic attack).
- A migraine attack.
- Fainting after certain situations (situational syncope) such
as:
- Blood drawing,
- Urinating (micturition syncope),
- Defecating (defecation syncope),
- Swallowing (swallowing syncope), or
- Coughing (cough syncope)
that trigger a reflex of the involuntary nervous system (the
vasovagal reaction) that slows the heart and dilates blood vessels in
the legs and cause one to feel nausea, sweating, or weakness just
before losing fainting.
Cardiac causes: Heart conditions that can cause
syncope or fainting due to temporary loss of consciousness
include:
To be sure, many of the causes of temporary loss of
consciousness can be detected by a careful history.
Dizziness after standing up in an older person suggests postural
hypotension. Temporary loss of consciousness after urinating,
defecating, or coughing suggests situational syncope. Cardiac causes
of temporary loss of consciousness such as aortic stenosis or
cardiomyopathy are suggested by the occurrence of the event during
exercise. Signs of weakness localized to certain areas of the body
with temporary loss of consciousness suggest stroke.
The blood pressure and pulse are tested in the lying, sitting, and
standing positions. Unequal blood pressures in each arm is a sign
of aortic dissection. The heart is examined with a stethoscope to
listen for sounds that can indicate valve abnormalities. The nervous
system is tested for sensation, reflexes, and motor function to
detect conditions of the nerves and brain. An EKG is done to check
for abnormal heart rhythms. Other tests may include echocardiograms,
rhythm monitoring tests (heart event recorders), and
electrophysiologic testing for abnormalities of the heart's
electrical system.
When heart conditions are not suspected, tilt-table testing can be
used to detect causes of temporary loss of consciousness. Tilt-table
testing involves placing the patient on a table with a foot-support.
The table is tilted upward and blood pressure and pulse is measured
while symptoms are recorded in various positions.
No treatment is needed for many non-cardiac causes of syncope
(such as postural hypotension, vasovagal reaction, and situational
syncope). The person regains consciousness by simply sitting or lying
down. The person is thereafter advised to avoid trigger situations,
to not strain while eliminating, to sit when coughing, to lie down
for blood drawing, etc.
Older people should have their medications reviewed and caution is
advised to slow the process of changing positions from lying to
standing. This simple technique can allow the body to adjust to the
new position (as the nerves to circulation of the legs adjust slower
in older persons).
Last Editorial Review: 12/3/1998 8:00:00 AM
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