Fainting: Encyclopedia - Fainting

Fainting

Fainting or syncope is a sudden (and generally momentary) loss of consciousness due to a lack of sufficient blood and oxygen reaching the brain. The first symptoms a person feels before fainting are dizziness and feeling hot. Moments later, the person's vision turns black and he or she drops to the floor (or slumps if seated in a chair).

Factors that influence fainting are taking in too little food and fluids, low blood pressure, hypoglycemia, physical exercise in excess of the energy reserve of the body, and lack of sleep. Even standing up too quickly or being in too hot a room can cause fainting.

Recommended treatment is to allow the person to lie on the ground with his or her legs a little elevated. As the dizziness and the momentary blindness passes, the person may experience visual disturbances in the form of small bright dots (phosphene). These will also pass within a few minutes. If fainting happens frequently, or if there is no obvious explanation, it is important to see a doctor about it.

More serious causes of fainting include cardiac (heart-related) causes such as an abnormal heart rhythm (an arrhythmia), where the heart beats too slowly, too rapidly or too irregularly to pump enough blood to the brain. This can be life-threatening.

Fainting can also be due to neurological disorders, stress, etc.

Fainting - Types

Fainting involves a temporary reduction of blood (and therefore oxygen) supply to the brain, resulting in a blackout. Many forms of syncope are benign and easy to associate with clear precipitants that can be avoided. Such precipitants can include many common situations and recreational drugs as well as therapeutic drugs.

Syncope can be brought on by a variety of heart-related and non-heart-related circulatory problems and activities, including simply getting up too quickly. Because of these many causes, there are subclassifications:

• vasovagal syncope, this is the common faint associated with a stress response of the autonomic nervous system which can either suddenly lower the pulse rate, the blood pressure or both together. It is one of the neurally-mediated reflex syncopes.
• carotid sinus syncope, also known as carotid sinus syndrome is associated with abnormal sensitivity to external pressure over the region of the nerve sensory organ at the bifurcation of the external and internal carotid arteries in the neck. Another reflex syncope.
• tussive syncope induced by coughing fits, also called larangeal syncope.
• An article in the August 2005 edition of the UK medical journal The Lancet was entitled Laughter-induced syncope.
• micturition syncope a faint during or shortly after urination.

Some of the other common medical conditions which may result in syncope are orthostatic hypotension (fall in blood pressure when standing) and heart rhythm problems (Cardiac arrhythmia).

See also

• orthostatic hypotension.

Category: Cardiology

Adapted from the Wikipedia article "Fainting", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki