Im a blood donor. I have been donating for about 2 years now. Both the first and the last time i went, i threw up.
Now the cardiovascular system and the digestion system arent heavily related as far as im aware.
So how come the bloodloss causes naseau and vomiting?
In: 3
That might be related to (conscious/unconscious) nerves about the blood drawing procedure. Can’t think of any other reason.
Blood loss can make you feel dizzy as your brain isn’t getting all the oxygen it wants. Being dizzy can induce nausea and vomiting. It could also be that your digestive system isn’t getting as much oxygen as it needs to digest the food so it gets rid of it.
Survival, certain symptoms make the body react as if poisoned. Most poisons are ingested, so the body removes a potential cause of the symptoms.
Basically your body is a machine getting inputs and making the best call it can with minimal information. Something is wrong, run the expulsion protocol.
Drawing blood results in a drop in blood pressure: since there’s less blood in your veins it doesn’t “push” as hard. Think of trying to squeeze a balloon, then letting out a bit of air and squeezing again. Easier the second time, right?
This drop in blood pressure can result in fainting—called a Vasovagal Syncope. But before you faint, you might experience several other symptoms, including dizziness and nausea. So vomiting from blood donation is you almost experience a Vasovagal Syncope, but not quite getting all the way there. Vomiting can actually help prevent fainting, because it causes a temporary rise in blood pressure.
Another cause of Vasovagal Syncope for some people is seeing blood, which is obviously is likely to happen while donating.
The best way to prevent vomiting and fainting is to stay well hydrated before and after your donation. Unfortunately this isn’t a guarantee fix and many people experience adverse reactions regardless.
Blood loss can cause a variety of symptoms, which your brain can detect, even if only subconsciously. It may simply classify these symptoms as “Something’s wrong.” but can’t tell exactly what’s causing them, so it defaults to “We’ve eaten something poisonous.”, because in prehistoric times that was a common cause of “Something’s wrong.”. So the solution is “get rid of the poison” by emptying the stomach of the “poisonous thing”, even if the diagnosis the brain reached is actually wrong.
That’s why vomiting can also be caused by such a variety of things, like inhaling or injecting drugs or a concussion. The brain knows “something” is wrong, but not “what” is wrong.
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