What causes fainting and what helps? Guide to vasovagal syncope

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Vasovagal syncope is a common condition that causes us to faint as a result of our body overreacting to certain triggers, like the sight of blood or extreme stress. Here’s what you need to know

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Vasovagal syncope is the medical term for fainting caused by not enough blood reaching the brain. It can affect a lot of people and has many different symptoms. Most of the time it’s not a serious condition but it’s important to monitor it, especially if you experience regular fainting.

What is vasovagal syncope?

Vasovagal syncope is caused by a sudden and temporary drop in your blood pressure and heart rate. This is the result of hyperstimulation of the vagus nerve, hence the term ‘vasovagal episode’. The vagus nerve plays an important role in the healthy functioning of the body. It is involved in the regulation of our breathing, digestive system, blood pressure and heart rate.

The drop in blood pressure causes the blood flow to our brain to lower, and this can make us feel temporarily unwell, or experience a brief loss of consciousness. This is known as syncope – or fainting.

Although vasovagal syncope in itself is harmless, it’s really the circumstances in which it occurs that can make it dangerous. Losing consciousness can lead to a traumatic fall or even a fatal accident, like while driving a car.

This phenomenon is very common among younger people aged 15-30, and especially women.

What are the symptoms of vasovagal syncope?

Vasovagal syncope usually sets in gradually but can also happen very suddenly. Before a vasovagal episode you might experience nausea, turning pale and sweating. Then, other symptoms gradually appear:

  • Blurred vision
  • Ringing in the ears (surrounding noises become almost inaudible)
  • Dizziness
  • Heart palpitations
  • Tremors
  • An inability to speak
  • Diarrhoea or abdominal pain
  • Headaches
  • Weakness in the legs
  • A loss of consciousness lasting a few seconds

Some symptoms, like headaches or severe fatigue, may last for several hours after the vasovagal episode.

What causes vasovagal syncope?

Vasovagal syncope is a frequent phenomenon and has many causes. There are physical triggers:

  • The sight of blood (from wounds or blood tests, for example)
  • Standing for a long time
  • A sharp pain
  • Intense fatigue
  • Extreme heat
  • Intense effort (from exercise, for example)
  • Prolonged fasting
  • Motion sickness
  • A lack of ventilation in a crowded environment

In addition to these physical factors, there are psychological factors like strong emotions or high stress levels.

In some cases, the drop in blood pressure may be a result of standing up too fast. This is more common in older people, as the vagus nerve's regulatory system can fatigue over time.

Certain drugs, especially those used for high blood pressure, can also trigger syncope.

There’s no treatment to prevent vasovagal syncope. The only solution is to avoid known triggers like stressful situations, prolonged fasting and lack of ventilation.

What to do if someone faints

When the first symptoms appear, the most important thing is to help regulate the blood flow by sitting the person down. If you can, lay the person down with their legs slightly elevated with a cushion. This will allow blood to flow back to the brain.

If you’re experiencing symptoms of vasovagal syncope, let the people around you know how you’re feeling. If you’re unable to sit down – like if you’re standing on public transport – ask for support to avoid a sudden fall.

In the majority of cases, the person experiencing a vasovagal episode will come round quickly after losing consciousness. If this is the case, reassure them when they wake up and encourage them to lie down for at least 10 minutes with their legs elevated.

If you think the person has lost consciousness for too long, there are certain signs to look out for indicating you should get emergency help. These include:

  • Not regaining consciousness
  • Not breathing
  • An irregular, very slow or even absent pulse

How long does it take to recover from

Although vasovagal syncope may seem alarming, the episode is usually brief. The accompanying symptoms usually disappear quickly. It may take a good 15 minutes before the blood flow to the brain is restored and this depends on the triggering event.

To recover more quickly from a vasovagal episode:

  • Sit or lie down
  • Contract the muscles of the legs and arms for 30 seconds and then release, to boost blood flow. You can repeat this process as many times as necessary

What to do if this is happening regularly

Vasovagal syncope usually recurs when a person is exposed to the same trigger. But this may indicate underlying problems, so you should always get medical advice if you suffer from recurrent fainting.

See a GP about vasovagal syncope

If you experience regular fainting and would like medical advice, book an appointment to speak to a doctor.

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