Fainting is a brief episode of unconsciousness caused by a sudden drop in blood pressure. The most likely cause of this sudden drop will either be some change in the blood vessels or the heartbeat itself.
Blood vessels continually adjust their width to ensure a constant blood pressure. For instance, the vessels constrict (tighten) 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 (expand), including extreme heat, emotional distress or pain. The lack of blood to the brain causes loss of consciousness.
Most fainting will pass quickly and won’t be serious. Usually, a fainting episode will only last a few seconds, although it will make the person feel unwell and recovery may take several minutes. If a person doesn’t recover quickly, always seek urgent medical attention.
Symptoms of fainting
The symptoms of a faint include:
- A pale face
- Heightened anxiety and restlessness
- Unconsciousness, for a few seconds
- Full recovery after a few minutes.
Occasionally, a collapse may be caused by a more serious event such as a stroke or a disturbance in the normal heart rhythm. A faint might be telling you something is wrong and further examination is sometimes important.
If a person complains of breathlessness, chest pains or heart palpitations, or if the pulse is faster or slower than expected, the person should see a doctor. Similarly, slurred speech, facial droop or weakness in any limbs are signs of a serious problem.
Causes of a drop in blood pressure
A temporary drop in blood pressure can be caused by different factors, including:
- Prolonged standing
- Extreme heat, which pushes 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 and fainting
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 that they 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.
- In an emergency, always call triple zero (000) for an ambulance if the person has not regained consciousness within a few seconds or recovered in a few minutes.
Hypotension and fainting
Low blood pressure (hypotension) is a condition characterised by blood pressure that is lower than normal or usual for the person.
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.
Blood vessels respond to gravity by constricting (tightening). This increases or maintains blood pressure when we stand up 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. For this reason, some people, particularly the elderly or those on blood pressure medication, should stand up from sitting or lying in bed slowly. This helps prevent fainting after sudden changes in position.
Causes of orthostatic hypotension include:
- Nervous system diseases, such as neuropathy
- Prolonged bed rest
- Irregular heartbeat (heart arrhythmia)
- Changes in blood pressure medication.
Where to get help
- Your doctor
- In an emergency, always call triple zero (000).
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.
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