Fainting is a temporary loss of consciousness, weakness of muscles, and inability to stand up, all caused by sudden loss of blood flow to the brain. Fainting is a relatively common symptom caused by a variety of problems relating to changes in blood pressure. The American Heart Association reports that fainting is responsible for 3% of all visits to emergency rooms and 6% of all admissions to hospitals.
Description
Fainting is a common symptom, also called syncope, vasovagal attack, neurally mediated syncope (NMS), neurocardiogenic syncope, and vasodepressor or reflex mediated syncope. Most simple faints result from an overstimulation of the autonomic nervous system that results in a drop in blood pressure and a slowed heart rate. Both of these conditions decrease blood flow to the brain, which causes a feeling of lightheadedness (presyncope) or a complete loss of consciousness (syncope). Fainting usually occurs in people who are standing or sitting upright. A person about to faint may also feel nauseated, weak, and warm. The person may experience temporary visual impairment, headache, ringing in the ears, shortness of breath, sensation of spinning, tingling in the extremities, and incontinence. A person experiencing presyncope may also appear pale or bluish. When consciousness is lost, a person usually falls down. This allows for more blood flow to the brain, resulting in a return to consciousness, usually within a few minutes.
Causes
Fainting is caused by a variety of factors, including stress, pain, overheating, dehydration, excessive sweating, exhaustion, hunger, alcohol, and drugs. Fainting may also be a side effect of some medications. A simple faint resulting from any of these factors is usually not a symptom of a neurological disorder.
Some people faint when changing positions, a condition known as postural hypotension. When people with this condition move from a lying position to a standing or sitting position, the sudden pooling of blood in the legs may cause a temporary decrease in blood circulation to the brain, causing a faint. This condition is common in elderly people who have been bedridden for some time and in people with poor muscle tone.
Some faints indicate serious disorders of the nervous or circulatory systems. Nervous system disorders that cause faints include acute or subacute dysautonomia, post-ganglionic autonomic insufficiency, and chronic preganglionic autonomic insufficiency. Fainting may also signal an irregular pattern of nervous stimulation such as micturition syncope (fainting while urinating), glossopharyngeal neuralgia (irritation of the ninth cranial nerve, causing pain in the tongue, throat, ear, and tonsils), cough syncope (fainting while coughing violently), and stretch syncope (fainting when stretching arms and neck). Faints can also indicate problems with the regulation of blood pressure and heart rate, and with disorders such as diabetes, alcoholism, malnutrition, and amyloidosis. Fainting can signal circulatory problems, particularly those that disrupt blood flow to the brain, as well as problems with the electrical impulses that control the heart, problems with the sinus node of the heart, heart arrhythmia, blood clots in the lung, a narrowing of the aorta, or other anatomical irregularities in the heart. Additionally, hyperventilation, usually associated with anxiety or panic, can result in a faint.
Diagnosis
Patients visiting a doctor because of fainting will usually have their blood pressure checked when they are lying down and then again after they stand up. If there is a significant decrease in blood pressure, it may indicate postural hypotension. A more sophisticated form of this blood pressure test is a tilt test, during which a person is strapped to a board that is rotated from the horizontal to the vertical position. Blood pressure is measured in both positions; an extreme drop indicates postural hypotension.
To test for circulatory problems, a physician may also use an electrocardiogram (EKG) to test for abnormalities of the heart beat. Exercise stress tests or wearing a Holter monitor for a day may also be performed to check for disorders of the heart. Fainting suspected to be caused by neurological disorders requires additional tests and evaluation by a neurologist.
Treatment
If a person faints while sitting, the body weight should be supported and the head positioned between the knees. If a person faints while standing, the individual should be carefully lowered to the ground and the legs elevated. Any tight clothes, including belts and collars, should be loosened. The head should be turned to the side so that the tongue does not obstruct the trachea and any vomit can be cleared from the airway. If the person stops breathing, cardiopulmonary resuscitation (CPR) should be started and a call should be placed to emergency medical services. A person who has fainted may benefit from cold compresses to the head and neck. After the person regains consciousness, he or she should remain lying or sitting for some time and should stand up only if no feeling of light-headedness persists.
A person who faints often will be treated for the underlying condition. Often, medications are used to control fainting; however, other methods may be helpful as well. In some people, changing to a high-salt diet or wearing support hose to keep blood from pooling in the legs prevents fainting. Some people may be able to prevent fainting by keeping glucose levels at a more constant level or by learning breathing techniques to prevent hyperventilation. Another technique for preventing faints is drinking enough fluid to keep blood volume high.
BOOKS
Icon Health Publications. The Official Patient's Sourcebook on Syncope: A Revised and Updated Directory for the Internet Age. San Diego, CA: ICON Group International, 2003.
OTHER
DeNoon, Daniel. Fainting Is a Serious Symptom. WebMD. January 14, 2002 (March 18, 2004). <http://my.webmd.com/content/Article/35/1728_96070.htm>.
The Mayo Clinic Staff. Simple Faint (Vasovagal Syncope). The Mayo Clinic. June 26, 2003 (March 18, 2004). <http://www.mayoclinic.com/invoke.cfm?id=AN00103>.
National Heart, Blood and Lung Institute. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 592-8573; Fax: (301) 592-8563. <http://www.nhlbi.nih.gov/index.htm>.
National Institute of Neurological Disorders and Stroke. P.O. Box 5801, Bethesda, MD 20824. (301) 496-5751 or (800) 352-9424. <http://www.ninds.nih.gov/>.
