Fainting Symptoms
Symptom Checker: Symptoms & Signs Index
Medical Author: William C. Shiel Jr., MD, FACP, FACR
Fainting (syncope) is the 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 terms, 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.
REFERENCE:
Fauci, Anthony S., et al. Harrison's Principles of Internal Medicine. 17th ed. United States: McGraw-Hill Professional, 2008.
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Other Causes of Fainting
Non-heart Causes: Syncope is most commonly caused
by conditions that do not directly involve the heart. These
conditions include the following:
- Postural (orthostatic) hypotension:
drop in blood pressure due to changing body position to a more vertical position
after lying or sitting
- 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
- Fainting after certain situations (situational syncope) such as
- blood drawing,
- urinating (micturition syncope),
- defecating (defecation syncope),
- swallowing (swallowing syncope),
- 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 fainting.
Heart Causes: Heart conditions that can cause
syncope or fainting due to temporary loss of consciousness
include:
Medications can cause
fainting by altering blood pressure or by affecting the heart.
