Blackouts

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What is a Blackout?


A blackout, also known as fainting, is the sudden loss of consciousness for a brief period. This is usually caused by insufficient blood flow to the brain and is often associated with low blood pressure (hypotension).


What are the Symptoms of a Blackout?


Before fainting, you may feel weakness or nausea. The following are also warning signs experienced just before fainting:

  • Feeling clammy and sweaty

  • Confusion

  • Light-headedness

  • Blurred vision

  • Yawning

  • Ringing in your ears

After fainting, you normally regain consciousness within 20 seconds, and you may feel weak for a short period afterward. You may also not remember what you were doing just before you fainted.


What Causes a Blackout?


Fainting (a blackout) is caused by a reduction in blood flow to the brain. This can be disrupted by several factors:

  • Triggers (e.g., heat, pain, sitting or standing up suddenly, an unpleasant sight or even swallowing)

  • Heart problems

  • Reflex anoxic seizures (common in children)

  • Low blood pressure (hypotension)

  • Low blood sugar levels

  • Medications

  • Dehydration


Can Blackouts be Prevented?


There is no specific treatment that prevents the onset of blackouts, but if a person is prone to fainting, they can either avoid known triggers or if they feel an episode coming on, lie down and lift their legs or sit down and put their head between their knees. This keeps blood flowing to the brain.


How are Blackouts Treated?


Treatment depends on the cause of the blackout. If there is an underlying health condition, then tests will need to confirm this and be treated accordingly. The tests that the doctor can order can include:

  • Blood tests

  • Heart rate monitoring

  • Echocardiography

  • Electrocardiography

  • Chest x-ray


Often, after fainting, no further treatment is needed, but measures to avoid future episodes can be taken, such as avoiding triggers.