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Fainting: Symptoms, diagnosis and treatment

What is fainting?

Fainting is a sudden and temporary loss of consciousness in which the person fainting falls or slumps because of reduced blood flow to the brain.

Fainting is relatively common, often affecting people who are otherwise healthy.

A person may not actually feel faint but feel lightheaded, which is called presyncope.

Many different conditions can cause fainting, also known as syncope.

These include heart problems such as irregular heart-beat, seizures, panic or anxiety attacks, low blood sugar (hypoglycaemia) and anaemia (a deficiency in healthy oxygen carrying cells), as well as problems with how the nervous system (the body's system of nerves) regulates blood pressure.

Some types of fainting seem to run in families. While fainting may indicate a particular medical condition, often it may occur in an otherwise healthy individual. Fainting is a particular problem for the elderly who may suffer serious injuries from falls when they faint. Most episodes are very brief. In most cases, the individual who has fainted regains complete consciousness within just a few minutes.

What causes fainting?

Fainting may have a variety of causes. A simple faint, also called a vasovagal attack or neurally-mediated syncope, is the most common type of fainting. It is most common in children and young adults. A vasovagal attack happens because your blood pressure drops, reducing circulation to the brain and causing loss of consciousness. Typically, an attack occurs while standing and is frequently preceded by a sensation of warmth, nausea, lightheadedness and visual "greyout". If the syncope is prolonged, it can trigger a seizure.

You may suffer from a simple faint due to anxiety, fear, pain, intense emotional stress, hunger or use of alcohol or drugs. Most people who suffer from simple fainting have no underlying heart or neurological (nerve or brain) problem.

Some people have a problem with the way their body regulates their blood pressure, particularly when they move too quickly from a lying or sitting position to a standing position. This condition is called postural hypotension and may be severe enough to cause fainting. This type of fainting is more common in the elderly, people who recently have had a lengthy illness that kept them in bed and people who have poor muscle tone.

Fainting can also be caused by the following:

  • Diseases of the autonomic nervous system. Your autonomic nervous system is the part of your nervous system that controls involuntary vital functions such as the beating of your heart, the degree to which your blood vessels are constricted, and breathing. Autonomic nervous system problems include acute or subacute dysautonomia, chronic post-ganglionic autonomic insufficiency and chronic pre-ganglionic autonomic insufficiency. If you have one of these disorders, you are likely to have other serious symptoms such as erectile dysfunction (inability to have or maintain an erection), loss of bladder and bowel control, loss of the normal reflexes of your pupils and decreased sweating, tearing and salivation.
  • Conditions that interfere with the parts of the nervous system that regulate blood pressure and heart rate. These conditions include diabetes, alcoholism, malnutrition, and amyloidosis - where waxy protein builds up in the tissues and organs. If you take certain high blood pressure drugs, which act on your blood vessels, you may be more likely to suffer from fainting. If you are dehydrated, this may affect the amount of blood in your body and your blood pressure. This may make you more likely to faint.
  • Heart or blood vessel problems that interfere with blood flow to the brain. These may include heart block - a problem with the electrical impulses that control your heart muscle - problems with the sinus node (a specialised area of your heart that helps it beat), heart arrhythmia (irregular heart rhythm), a blood clot in your lungs, an abnormally narrowed aortic heart valve, and certain other problems with the structure of your heart.
  • Conditions that may cause unusual patterns of stimulation to particular nerves. These include micturition syncope (fainting during or after urinating), glossopharyngeal neuralgia (fainting due to inflammation and pain in a particular nerve to the mouth), cough syncope (fainting after intense coughing) and stretch syncope (fainting that occurs when stretching the neck and arms).
  • Hyperventilation. If you become intensely anxious or panicky and breathe too quickly, you may faint from hyperventilation - taking in too much oxygen and getting rid of carbon dioxide too quickly.


WebMD Medical Reference

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