Fainting

Alternative names:

lightheadedness - fainting; passed out; syncopal episode; syncope

Definition:

Fainting is a temporary loss of consciousness as a result of transiently decreased blood flow to the brain. Lightheadedness is a vague feeling of dizziness or a feeling like a person is going to faint.

Considerations:

Fainting (syncope) can be caused by any condition causing a reduction of circulating blood flow to the brain. The cause of fainting should be evaluated by a health care provider.

Fainting or syncope is characterized by sudden pallor, loss of consciousness, and occasionally slight twitching or convulsive movements. For a parent, seeing their child faint may be a terrifying experience.

A simple faint (vasovagal faint) is rarely preceded by pain, pressure, constriction in the chest, or shortness of breath. It can be preceded by weakness, giddiness, nausea, dizziness, and a sense that the surrounding noise is growing fainter and fainter.

Pathologic fainting or syncope may also be associated with heart conditions, most often abnormal heart rhythms (arrhythmias).

Common causes:

Lightheadedness can accompany mild illness such as the flu or the common cold, and can accompany anxiety. Lightheadedness without other symptoms is usually not serious.

Actual fainting can be caused by any condition restricting blood flow to the brain; this can be positional, physiological (an automatic body response to a stimulus), or a result of drugs or activity. The more common causes include:

• rigid standing at attention
• arising quickly from a prone position
• pressure on the neck (tight collar)
• abnormal heart rate or rhythm
• low blood pressure (hypotension)
• severe pain, injury or fright
• alcohol or drugs including anxiolytics, antihistamines, antihypertensives, vasodilators, decongestants, central nervous system depressants
• strenuous coughing, straining during a bowel movement or any other Valsalva maneuver (forced exhalation with closure of mouth and nose)
• hyperventilation

Note: There may be other causes of fainting. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as time course, aggravating factors, relieving factors, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for fainting, occurring alone or in combination with other problems.