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Fainting – 3 Possible Causes

Syncope is a temporary loss of consciousness usually related to insufficient blood flow to the brain. It’s also called fainting or “passing out.”

It most often occurs when blood pressure is too low (hypotension) and the heart doesn’t pump enough blood to the brain. It can be benign or a symptom of an underlying medical condition.

Fact: Although brain comprises only 5% of the body’s weight, it consumes 20% of the body’s energy.

A Trigger

The most common cause of fainting is insufficient blood flow to the brain. Blood pressures are precisely regulated for our body but many different things cause a sudden drop in blood pressure. An external trigger may temporarily cause autonomous nervous system to stop working properly and resulting in low blood pressure and fainting (Neural Mediated Syncope or Vasavada Syncope).

The trigger may be:
• an unpleasant sight
• heat
• sudden pain
• coughing
• sneezing
• laughing
• sitting or standing up suddenly – known as postural tachycardia syndrome (PoTS)

Insufficient Oxygen on Blood

If there’s not sufficient oxygen in the blood, even if the blood flow to the brain in adequate a person can faint. High altitude pilots and mountaineers, for example, are at risk of hypoxia-induced fainting. However, anything that impairs the delivery of oxygen to red blood cells can result in fainting.

Inhaling toxic gas like carbon monoxide impairs the ability of hemoglobin to bind oxygen inducing fainting quickly.

Disruption of neuronal function

The third cause of fainting is the disruption of neuronal function in the cerebral cortex. Toxins such as alcohol or anesthetics, can suppress normal electrical activity in the cerebral cortex resulting in sudden loss of consciousness.

Similarly, inadequate supply of glucose to fuel the energy requirements of the neurons will result in fainting. Epilepsy and seizure are caused by wildly uncontrolled firing of neurons in the cerebral cortex resulting in loss of consciousness.

Take away…

So fainting is a sign of many different medical issues in the brain and body. But it can also happen in perfectly normal and fit individuals. For example, very fit athletes who have low resting heart rates can be prone to fainting upon suddenly rising from a seated position.

Even soldiers, who are among the most fit of all, faint when forced to stand at attention in the sun for long.

So knowledge is half the battle in prevention of fainting. Patients of multiple fainting spells should definitely see a neurologist and determine the cause of the fainting and understand the warning signs of fainting and can learn how to avoid it.

Dr. Vishal Jogi

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