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10 February, 2010

Home > Fact sheets by category > Diseases and conditions > Brain and nervous system > General > Fainting.

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Fainting

Fainting is a momentary episode of unconsciousness caused by a sudden drop in blood pressure.

Blood vessels continuously adjust their diameter to ensure a constant blood pressure. For instance, the vessels constrict when we stand up to counteract the effects of gravity. Temporary low blood pressure can be caused by various events that prompt blood vessels to dilate, including extreme heat, emotional distress or pain. The lack of blood to the brain causes a lapse of consciousness.

Usually, a fainting episode only lasts a matter of seconds, with recovery taking a few minutes. If a person doesn’t recover quickly, always seek urgent medical attention. The collapse could have been triggered by a more serious event such as cerebral haemorrhage (stroke).

Symptoms
The symptoms of a faint include:

Dizziness
Light-headedness
A pale face
Perspiration
Heightened anxiety and restlessness
Nausea
Collapse
Unconsciousness, for a few seconds
Full recovery after a few minutes.

A range of causes
A temporary drop in blood pressure can be caused by different factors, including:

Prolonged standing
Extreme heat, which shunts blood away from the main circulatory system and into the vessels of the skin
Emotional distress
Severe pain
The sight of blood
The sight of a hypodermic needle
Other events that a person may find distressing.

What to do if you feel faint
If possible, lie down and elevate the feet. This may prevent a loss of consciousness. Fresh air can also help, especially if you are feeling hot. If it is not possible to lie down, put your head down as low as possible.

If you do faint, remain lying down for ten minutes. Sit up slowly when you need to get up.

First aid
First aid treatment for a person who has fainted includes:

Help the person lie down. A person who has fainted in a chair should be helped to the ground.
If the person is unconscious, roll them on their side. Check they are breathing and have a pulse.
If possible, elevate the person’s feet above the height of their head.
If the fainting episode was brought on by heat, remove or loosen clothes and try to cool the person down by wiping them with a wet cloth or fanning them.
Assess the person for any potential injuries if they have fallen.
Dial triple zero (000) for an ambulance if the person has not regained consciousness within a few seconds or recovered in a few minutes.

Orthostatic hypotension
Blood vessels respond to gravity by constricting. This increases or maintains blood pressure when we stand from a sitting or lying position.

Orthostatic hypotension means that the blood vessels don’t adjust to a standing position but instead allow the blood pressure to drop, which can trigger a fainting episode.

Causes of orthostatic hypotension include:

Nervous system diseases, such as neuropathy
Prolonged bed rest
Dehydration
Irregular heart beat (heart arrhythmia)
Changes in blood pressure medication.

Hypotension
Low blood pressure (hypotension) is a condition characterised by blood pressure that is lower than normal or usual for a particular individual.

Hypotension can be caused by a variety of factors including heart disease and abnormal heart rhythms, some infections, dehydration and medications for high blood pressure or certain heart conditions. Low blood pressure can also be caused by a rare disorder of the adrenal glands called Addison’s disease. Frequent fainting spells or sensations of light-headedness need to be medically investigated to check for underlying causes.

Where to get help

Your doctor
In an emergency, dial triple zero (000) for an ambulance

Things to remember

Common causes of fainting include heat, pain, distress, the sight of blood or anxiety and hyperventilating.
Lying the person down will often improve the person’s condition.
Frequent fainting spells need to be medically investigated to check for underlying causes.

You might also be interested in:
Blood pressure.
Dizziness and vertigo.
Long QT syndrome.

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