View Full Version : Wounds and Bleeding in Low and Microgravity Environments

05-15-2011, 06:08 PM
I was wondering how people would bleed in low and microgravity environments.

In other words, if you had a gun fight or surgery in space or on the moon, without artificial gravity, what would it be like?

05-15-2011, 11:07 PM
For one thing, the immune system doesn't work as well in space, so bleeding won't stop as fast due to reduced blood platelet counts. Air pressure is likely to be lower, so that would somewhat increase the blood flow. Blood will also float around the ship and get into things where you don't want it, and if the person has a blood-borne disease it could spread to anyone who swallows or inhales some.

05-16-2011, 12:10 AM
The heart is a pump, of course, and the blood will exit the wound or incision because the heart is pumping it into arteries and veins which are no longer intact. That won't change.

The blood will not flow downward, though, because of the absence of gravity. I can't remember which one it was, but one of the earlier Star Trek movies had globules of purplish blood (Klingon?) suspended in air during a battle scene, and it was applauded as how it is likely to be.

Maryn, who avoids gunplay in space whenever possible

05-16-2011, 06:43 AM
Crikey, what would happen if you were cut/shot in a vacuum? Bad things, I'm guessing...

05-16-2011, 10:28 AM
Crikey, what would happen if you were cut/shot in a vacuum? Bad things, I'm guessing...

If you were in a vacuum then being cut would be the least of your worries :).

If you were in a space suit, one potential issue is that current suits are very inflexible, so if you were cut in such a suit the air pressure inside could be too high to allow you to use your hand to try to stop the bleeding until much of the air had leaked out.

05-16-2011, 12:40 PM
Yeah, I'm not sure gravity or lack thereof would affect bleeding as much as low or zero atmospheric pressure. Field surgery in a vacuum or an alien environment would be impossible, stripping the pressure suit to get to the wound might well kill the patient, they'd have to slap a patch over the suit puncture and get him into a pressurized environment to work on him. Or the medic would have to bring a sealable capsule to the patient.

-Derek (who writes such scenarios)

05-16-2011, 02:56 PM
Hey, they reckon you have up to 10 seconds of useful consciousness in a vacuum before hypoxia sets in... and they reckon your skin only swells to double its size, doesn't burst... but yeah, obviously you'd be up the creek. Still, interesting. Explosive decompression, even in a space suit, would probably be instantly fatal, no?

05-22-2011, 02:04 AM
Hmmm, due to internal and external pressure differences I tend to think that any wound in a low pressure environment might be life-threatening. Arterial blood is under high enough pressure that it sprays on Earth. I've seen it spout from the back of my hand when someone was trying to put in an IV and just nicked the artery rather than spear it.

Venous blood isn't under as much pressure, but I think it would still tend to spray because it's still under some pressure.

Thus, I think you'd tend to lose blood and dehydrate at an extraordinarily faster rate in a low or no pressure environment than you would in a normal or high pressure one. Shock would set in extremely rapidly as blood pressure crashed along with attendant cyanosis (I think that's the word for extreme blood loss - I'm a writer not a doctor, Jim).

In my opinion, of course.

05-23-2011, 04:32 AM
I note that "low gravity" and "low pressure" are being conflated in this discussion, and they're not the same thing, tho we tend to equate both with being in outer space.

Gas or liquid will explosively decompress. Relatively solid things like bodies don't. If you've ever seen euthanasia in a hypobaric chamber -- what happens is rapid unconsciousness, followed by a little capillary bleeding from the whites of the eyes (and less often, a few drops from the nose).

05-23-2011, 06:50 AM
I've never seen any kind of euthanasia, actually. Is that, er, not normal?

The effects of pressure are pretty freaking fascinating.

05-23-2011, 07:27 AM
I know that in the case of space suits they're actually kind of "compartmentalized" at the joints (rubber seal that "suctions" to the body), so that if pressure is lost in the suit it keeps the whole suit from depressurizing. In a real life case, where Joseph Kittinger jumped from the edge of space, the pressurization in his glove failed, and caused his hand to swell up like a balloon.


Assuming the rest of your suit could maintain pressure, a local loss of pressure would cause injury but it wouldn't be immediately fatal. It wouldn't surprise me, if a combat in zero gravity, would involve people wearing pressure suits that are designed to have levels of redundancy and probably additional life support built in (e.g. built in tourniquets, automatic drug/morphine injectors, etc.).