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For anyone who has ever passed out, the increasingly blurry vision right before losing consciousness is almost as terrifying as waking up with no recollection of what just happened. It’s a feeling I am familiar with, having fainted after a routine flu shot last fall—and before you ask, no, I’m not afraid of needles. Fortunately, at the time, I was already seated and in the middle of a hospital, and I’ve had no repeat episodes since. Nonetheless, this unprecedented experience piqued my interest into what medical experts call neurally mediated syncope (NMS), the most common form of fainting.

Syncope, the medical term for fainting, can be differentiated into a number of different types based on cause—for example, abnormal heart rhythms can lead to fainting. Neurally mediated syncope, on the other hand, does not have a specific cause or trigger. NMS, also referred to as vasovagal syncope, occurs when blood pressure drops suddenly and results in temporary insufficient blood flow to the brain, prompting a blackout. The body simply overreacts and shuts down, similar to a electrical device malfunction, only to reset itself a few moments later. While NMS can be caused by fear, other likely culprits include pain or dehydration (as I later realized, I had been taking medication with dehydration as a side effect prior to my fainting episode). From an evolutionary perspective, NMS is thought to have conferred a survival advantage for our human ancestors in dangerous circumstances.

Heat exhaustion and dehydration are common triggers for fainting.

Image source: Chris Hondros

Despite the concern surrounding syncope, NMS is generally harmless—in fact, the greatest risk posed by fainting is bodily injury from a fall while unconscious rather than the episode itself. If you ever begin to feel dizzy, healthcare professionals recommend lying down or lowering yourself to the ground to minimize injury. That said, if low blood pressure seems to be the problem, prescription medication or increasing salt intake can help correct the issue. If fear is a factor, such as during a vaccination or blood draw, always inform your healthcare provider so that they can place you in a reclining position and monitor your condition immediately after the event.

Fainting can be disconcerting, but without any other symptoms, the occurrence tends to simply be a rare reflexive response to a trigger like heat, pain, or fear. With a little adjustment to your daily routine, avoiding a repeat episode should be relatively easy. Of course, if you think your fainting spell is the result of a more serious condition, such as a cardiac issue, contact a medical professional immediately.

Feature Image Source: Migraine by Sasha Wolff

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