What Causes Vasovagal Syncope?

Medically Reviewed on 4/21/2021

Springtime is a new adventure for many first-year medical and nursing students. After a semester in the classroom, they are let loose to observe the real world. Invariably, the same scenario plays out.

All is well as they enter the operating room. The anesthesiologist is finishing putting the patient to sleep, and the student is set to observe an actual surgical procedure for the first time. The room is excessively hot to keep the patient warm on the table. The surgeon puts sterile drapes across the body, the bright lights are turned on, and the only noise is that of the ventilator breathing for the patient. The surgeon turns to the anesthesiologist, asks permission to begin, and makes a long, slow incision into the body with the scalpel edge.

Meanwhile, the student's cool veneer begins to show cracks. The heat of the room has made sweat start to stream on the forehead. The lights start to blur, and voices in the room become distorted. Sickening nausea, lightheadedness, the vision fades to black, and all this is quickly followed by the sound of the first-year student hitting the floor in a faint.

It's not the first time this has happened; one of the surgical nurses wanders over and checks on the student, who gradually wakens and sits up. In a few minutes, the newbie is escorted into the break room where the nurse helps soothe the damaged ego and reassures the poor soul that this is the standard operating procedure. Many people pass out with their first operation.

What causes vasovagal syncope?

Vasovagal syncope is a common cause of fainting. The vagus nerve is overstimulated and causes the body's blood vessels to dilate and the heart to slow down. This anti-adrenaline effect decreases the ability of the heart to pump blood upward to the brain against gravity. Without blood flow, the brain turns off. In Victorian England, when this happened because young ladies' sensibilities were easily offended, this was called a swoon.

Fortunately, the body is able to correct this temporary problem and return normalcy to the circulatory system in a matter of seconds. Unfortunately, that time delay allows the faint to happen, and while the fainting itself is not a big deal, the potential complications may be. Falling is tough as you get older, kids bounce but adults tend to break. Imagine fainting while driving a car or swimming in a lake. While the grizzled veterans of the medical community laugh at the "routine faint" and then welcome the new students into their fraternity, blacking out is not something to be taken lightly.

People faint at the sight of blood. Parents faint when their kids get immunized. Older people faint in church. Many types of emotional and physical stressors can stimulate the vagus nerve to do damage. But on occasion, the cause of the faint is not vasovagal syncope but something more serious. Encouraging the person to seek medical care or calling 911 may save a life. While it may be an inconvenience or sometimes an embarrassment to a patient, being unconscious is not normal. It may be easily explained...but it's not normal.

And if you think you couldn't work in a hospital because you become queasy and lightheaded at the sight of blood, take a look at your doctor or nurse and imagine them passed out on the floor and consider joining the club.

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