Vagal Nerve Fainting

People lose consciousness for a variety of reasons and from a variety of causes. Some are psychological, i.e. the fear response causes them to faint, or physical, such as the fainting that occurs when we over exert ourselves. Vagal nerve fainting (also known as vasovagal syncope) is quite simply any loss of consciousness caused by the vagus nerve.

The vagus nerve runs directly from the brain stem, in front of the ears and down the neck towards the chest and abdomen. It branches off in several places to provide communication with the brain to a number of organs, such as the heart and the stomach. Its main function is to direct blood towards the digestive system when food is eaten, but if it is overactive then the vagus nerve can take too much blood away from the brain, causing a loss of consciousness (vagal nerve fainting).

This type of fainting is not generally limited to people with ‘defective’ vagal nerves, but it is a reaction that can happen to any human. Most of us have experienced significant dizziness or a ‘head rush’ after vomiting which means we need to lie down. Some of you reading this will have fainted after vomiting too and this is a classic vagal nerve reaction. Similarly, if we have a particularly large bowel movement the vagus nerve can become over stimulated again, taking blood away from the brain to help with what’s happening elsewhere in the body. It’s an unpleasant reaction and one that can be embarrassing but medical professionals recognize it readily and know the very simple treatments required for vagal nerve fainting like the backs of their hands.

So what does it feel like to have a vagal nerve fainting episode? You’ll most likely feel dizzy, nauseous and as if you have a head rush. Your hearing may feel ‘muffled’ and your eyesight blurry or even tunnel-like. You may try to articulate that something is wrong, but the words come out garbled. Don’t worry, this is just a result of your brain not having enough blood, but once you return to consciousness this will right itself. You will also most likely feel hot at first, but then cool and clammy once you wake up. Don’t try to get up right away but relax for a while, have a little water and get some cool, fresh air.

Over stimulation of the vagal nerve can also be triggered if a person is ‘squeamish’ i.e. they may pass out at the sight of blood, something particularly gory or sexually explicit. This type of response is only a worry when it happens very often, or if the individual has a heart condition, as the vagus nerve causes slowing of the heart when overstimulated. If you are fainting regularly then you should visit your doctor as soon as possible to find out what the possible causes are and what treatments are available to you.

Comments 26
  1. What are the very simple treatments? Information quite deficient. No link provided (I'm not a medic)

  2. The information is general for many experiences but still does not answer my particular experiences which still has me baffeled and the doctors have no definit answer.

    Thank you, just the same.

  3. This article was more informative than what the doctor at the emergency room, now I know exactly what happened to me, thank you!

  4. Occasionally while eating I get the head rush mentioned above and have actually passed out twice momentarily. Most of the time when the head rush occurs I do not pass out.

  5. I have been bothered by these "spells" for years. I found that a dose of pepto-bismal stops the reaction in its tracks – I don't know if it will work for anyone else, but it is worth a try. My doctor said it was fine to use – just don't over do it. I carry the tablets in my purse and chew on one or two when I get that "feeling" coming on. The med seems to soothe the nerve.

  6. Excellent explanation but no recommendations except to lie down.

    I'm looking for some way to avoid or stave off the feeling. You mention that doctors know "very simple treatments" – but neither my PCP or my "gastro" doctor have been able to do that.

    The suggestion re: Pepto – that contains a great deal of "aspirin" – likely to cause other problems. Also since that is a med to help stop diarrhoea – this would increase rectal pressure and increase the vagal nerve spasm. No?

  7. I was scheduled for a pacemaker. A different cardiologist diagnosed being not a heart problem but fear of the chest pain from gastric ulcers being a heart attack. I could have diagnosed from reading this article as it describes perfectly the situation.

  8. Happened to spouse after bowel movement. Totally passed out. Went to E R then was diagnosed with same. Article brought us some peace of mind!

  9. I have what may be a vagal nerve problem. My doctor has dismissed it as just one of those things. If I am lying on my back and roll on to my left side and prop myself up on my elbow and lean across with my right hand to reach the alarm clock, I fell as if I am going to black out. If I stop what I am doing and resume my original position the "head rush" subsides and all is well again. This problem also occurs when in my car and I want something out of the glove box in front of the passenger’s seat. Left elbow resting on center console, between the seats, reaching with my right hand to open the glove box, the same black out sensation, stopped again by quickly returning to my seat and regaining my original upright posture. It appears that any action of propping myself up on my left elbow and reaching across to my left, causes this head rush. My doctor wants me to have the blood vessels in the area checked, which returned a nothing wrong result.

    Could my problem be caused by the vagal nerve being trapped by the actions described.


    Bill W.

  10. This is a good description. I am recovering from a stomach virus that landed me in the hospital. I blacked out 5 times during vomiting episodes. Hit my face really hard the last fall. Gave me fluids and zofran. Now it makes sense that my heart rate and blood pressures dropped quickly. The ER doctors told me I had Vagul Episodes.

  11. Articles enlightening, more detailed than I was given by Emergency Room Cardiologist. After I suffered attack on June 5th which caused me to black out, fall and break my right ankle tibia and fibia resulting in bone repair surgery, titanium plate and screw installation to stabilize bones. I have had four splints and am wheel chair bound with no weight bearing for two months. Possible surgery to remove screw in September and probably. Because of the nature of the break and surgery, I have had to take/inject blood thinners. These injections resulted in a GI hemorrhage which hospitalized me for another four days with rehab to boot.

  12. This information was helpful as were the comments. My husband has had several of these episodes, mostly with a bm, but vomiting caused it a couple times. We immediately try to get some alka-seltzer in him, but maybe we should try pepto instead. When he does go out completely, I yell at him, smack him in the face (I know that sounds cruel, but it works) and this last time I rubbed ice directly on his face. Putting his head down between his legs doesn’t prevent him from going out and I’m afraid he’ll pitch forward off the toilet – most times he happens to be on the toilet. One time, he went down in the hallway and I couldn’t move him, so I called 911. This is a very scary situation, for both of us, and I’m worried about waiting too long to call for help. After the most recent episode, we bought some smelling salts to keep handy and will see if those bring him around quicker.

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