Why do I tend to pass out after an injury?

Factual Questions
1

Standard disclaimer: I am not looking for medical advice. Nothing that is said here will be taken as such. I do not plan to use this advice in lieu of a doctor’s. And anyway no doctors are involved here, the incident has passed, I’m just fine. I’m really more curious than anything.

Let me first say that I am not a fainter. I have fainted exactly twice in my entire lifetime, and came close a third. The first time I fainted was due to a diet I let me friend talk me into that my body disagreed with. (High protein, high fiber, no sugars, supposedly good for weightlifting, which was the other thing I let him talk me into that gave rise to the diet in the first place.) The first time I almost did was almost three years ago, from a slightly traumatic injury. The most recent time was two days ago, from a much less traumatic (but rather more embarrassing) injury.

The first time: I’ll spare you the details execpt to say that I’m just really stupid when I don’t think ahead. The end product was a box cutter through my index finger. Fortunately it didn’t sever anything important, just the fleshy part where finger meets palm. When it happened I immediately clamped down on my hand (there was no pain, I didn’t see the wound, but I knew it was there, as the way events played out, there was no other possible outcome.) I went to the washroom and turned on the tap to clean out the wound; it was pretty gross, seeing this hole in my finger that slid around like rolling the top of a sandwich bag between your thumb and forefinger to get the opening to separate. Anyway, I packed it with some paper towel (all that was available in the washroom; the first aid kit was elsewhere in the shop) and then told someone about it, then had it looked at by the first-aid trained staff member back in the washroom where he began to dress it with gauze. It was at that point that I began to feel very faint. I never actually passed out but I recognized the symptoms and fought it off as best I could. Given a few minutes I was back to rights.

Now, last Wednesday. Taking a company-paid course on small engine troubleshooting and repair. I drop something on the floor. Bend down to pick it up, then straighten myself only to prang the back of my head on the corner of the fold-out leaf of my neighbour’s metal work desk. It didn’t hurt a whole lot – I’ve certainly had worse lumps. But the corner was just sharp enough prick the scalp. It turned out to be a pretty miniscule wound – not much more an the point of a slightly dull pencil, really, but head wounds are real bleeders, so it looked a lot worse than it was. I got back up, hand held to head (and then with paper towel when someone offered) and I seemed okay for a few minutes. Then once again I started to feel really faint until, if not for the grace of the teacher, I would have fallen over when I passed out. I don’t even remember being laid down on the ground; I just remember asking “I didn’t fall, did I?” Anyway, I laid there for a few minutes (really, longer than I felt necessary, but the teach, who is also our national tech support guy and the main first aid guy here, insisted.) Long story short, I was fine after a few minutes and there was no lingering queasiness or anything.

So … what gives? Why did I pass out? I’m not really squeamish at the sight of blood. (Yeah, mutilated bodies and stuff will probably make me want to hurl, certain types of wounds in particular, but on the whole I’m pretty stout.) I’ve had nosebleeds that bled worse than my head did and felt nary a twinge. I can watch the goriest horror movies without batting an eye. And while the knife through the finger was kinda traumatic in its own way, smacking my head against something is not – heck, I’ve probably smacked my head against things from not watching where objects were when I dipped below their altitude than any other type of minor blunt injury. The only difference is this one bled. Not buckets or anything, probably about as much as a minor-to-middling nosebleed. I didn’t go into shock, either; this one stung, so it wasn’t bad enough for my body to say “Whoop, better keep you lucid and focused so you can tend to this before I spring the pain on you.”

It just has me baffled. I’m just not the fainting type, so what’s the big idea with my body betraying me like that? It’s completely uncalled for.

2

I have the same issue. A friend once said “Oh, Vagus response.”
Take a look here: Vagus nerve - Wikipedia especially the section on “Physical and emotional effects”

3

Well, that does seem to explain what’s happening, but it doesn’t really explain why. Why is my vagus nerve getting all uppity over a little bump on the noggin? It’s not like I was particularly stressed, I was well hydrated, experiencing no emotional turmoil – really, I was just pleasantly engaged in tearing apart an engine. If anything, I was treating my vagus nerve with all due respect, so all I can think of is that my vagus nerve is an asshole.

4

*The vagus nerve is part of the autonomic nervous system, which controls smooth muscle (involuntary) response.
When catecholamines, which are the chemicals responsible for the “flight or fight” reaction are released, the heart rate goes up. As the amount of stimulant decreases, the vagus slows the heart, bringing it back into the normal range. Sometimes it over shoots, and the person goes down due to low blood pressure.

However, another possibility could be that with injury, one group of the neural chemicals release are endorphins. They have a very short term effect, but are very potent. You may have an over abundance, causing a drop in blood pressure.

  • This is a very simplified explanation.
5

You’re not alone. It happens to me sometimes too. I learned to warn medical personnel that I might keel over if they draw blood, so they usually have me lie down. It doesn’t happen every time, but it does still happen every once in a while. Apparently, my uncle has the same problem, so maybe there’s a bit of a genetic component to it.

Like you, I find it extremely annoying since I don’t have any particularly strong emotional response to the sight of blood. I’ve had big gashes that leaked all over the place which didn’t give me much of a problem, but have gone right over from a tiny cut on the edge of my hand that bled a surprising amount for such a small wound but didn’t amount to much blood loss at all.

Frankly, I figure it’s probably going to get me killed someday. Two situations I can think of that might produce blood and further danger are: getting a bad cut with no one to help around and no quick way to a hospital after I wake up, and a fight. While I have been in fights that produced both cuts and bloody noses and I haven’t passed out in the middle of festivities, I’m worried about it happening sometime in the future.

(I swear, I’ve had guns pointed at me twice and I barely blinked, I dealt with a guy trying to stab me without a problem, but a little cut on my finger makes me want to pass out? What the hell’s up with that?)

6

So it’s an autonomic thing. I guess that should have been obvious. But I’ll be damned if it isn’t embarrassing. Right in the middle of class, for cryin’ out loud!

So, is an overabundance of endorphins a good thing or a bad thing? And is it possible to get my body to cut it the hell out?

Good to know I’m not a freak though. I mean, I know there are others that do, but it’s the sort of thing you expect to see of women in 1940s films, catching the vapors (possibly turning Japanese) and all that. I’m a guy. I’m not supposed to do that. It’s slightly emasculating. :slight_smile:

7

Yep, been there done that.
Poked in the eye pretty good caused the same thing. Very frustrating and seemingly girly type reaction, hey?
Also, a deep cut to my pinky knuckle caused the same reaction.
Both times I didn’t pass out but got really light headed and somewhat sick to the stomach. I’m such a woman.