nemonclature: Blade tied to a chair, looking up at camera (look up)
[personal profile] nemonclature
The human body contains about 5 litres of blood, allowing for differences in body weight. A donor usually gives about 8-10% of their blood (so approx 500ml). 15-30% (1.5 litres) and you'll feel sick, go pale and your skin will start feeling cold. 30-40% (2 litres) and your heart starts beating faster you'll probably need a transfusion to recover. Over 40% your probably a goner.

In one sitting, you can probably drink 1-1.5 litres comfortably. The stomach can expand to about 4 litres, which is why people can drink a gallon of milk without exploding (but then usually vomit it up after because... what did they expect?)

You can bleed out from the carotid (neck), brachial (arm) or femoral (leg) in about a minute. But arteries are fairly difficult to get at. In the wrist, you'd have to slice vertically down your artery to bleed out with any speed, so from a vamp bite you're talking a few hours, plus the possibility of clotting staunching the flow.

In the neck you'd probably hit veins or even the windpipe first, depending on your aim. Most the time they bite the meat of shoulder, not the pulse point (i.e. artery) which is harder to get to, higher on the neck.

As for the femoral, it's fairly difficult to get your face into someone's groin if accosting outside of a naked sexytimes scenario.

Also vamp teeth are fairly thin and short. It's questionable how far they'd even penetrate considering the layer of fat we all have under the skin before you even get to any good stuff.

So while they may nick an artery, we're not looking at the bleeding out in minutes that you get from severing one fully. You will bleed, and suction will probably induce a steady flow, but you're unlikely to bleed out from a bite wound.

So overall, that equals: a vampire can safely drink as much as the victim can safely lose. The victim won't die, but will feel woozy and need to drink electrolytes or take iron tablets to recover. The wound is going to need pressure and treating, if an artery is nicked, probably in the hospital so they can make sure it heals ok, but if no artery is touched, then just like you would a normal cut. It should clot fine and NO ONE NEED DIE.

The whole, vampire grabs a person by the neck and drains them in seconds, dropping their dead body to the floor? NO. It would be, vamp grabs by neck, stretches head awkwardly to side to get at carotid. Bites, gets blood EVERYWHERE like it's being sprayed out by a fucking garden hose. Makes a massive mess and a few minutes later, the person dies. They would not be able to drink that much blood without vomiting it back up again a la the milk gallon drinking fools. Not a sexy look, I'd imagine.

IF they have anticoagulants in their saliva, then, provided they do pierce an artery, (which isn't easy) passing out followed by death is probably inevitable without medical treatment. Though still, not going to be instantaneous, but a few minutes to an hour depending on severity of bite.

For the ones that rip the entire throat out with their teeth, well yes. Obvs that kills.



Follow up for this would be, if a vamp can drink, let's say 1 litre per person to be on the safe side, then they need to hit up 5 people per night to fully replace the blood in their body. Though, we don't know what happens to blood once in a vamp's body exactly. Maybe since they're dead, they can't generate new blood, only use what they have until it dies. Red blood cells live for about 4 months, so 5 people every 4 months, or, since they could take just over a litre from each person, that's basically hitting one person a month for just over 1 litre of blood.

One person a month. Seriously, couple of iron tablets and some Lucozade and they're fine. NO BIG.

Date: 2016-02-04 02:00 am (UTC)
out_there: B-Day Present '05 (Default)
From: [personal profile] out_there
Bites, gets blood EVERYWHERE like it's being sprayed out by a fucking garden hose.

You know, I'm pretty sure I've seen those vampire movies. *laughs*


One person a month. Seriously, couple of iron tablets and some Lucozade and they're fine. NO BIG.


Hee! I love the amount of logical thought that you've gone into here. It does lend weight to the whole idea of non-fatal vampires. People possibly passing out from shock and blood loss, but death-within-seconds is less likely.

Date: 2016-02-04 03:44 am (UTC)
kiki_eng: two bats investigating plants against the night sky (Default)
From: [personal profile] kiki_eng
This is super-interesting and has me thinking about the mechanics of death by vampire, like, what if the fangs carry a poison? ...because there is that swooning thing that happens. And, okay, is there a rate of blood flow/suction that would mess up the heart's function? Could they be killing people that way?

How much does what kind of blood they're getting matter? If they're after it because they can't generate their own blood do they have to have blood that's compatible with their type? ...can they taste that? ...or did they spend years not being able to figure out why sometimes they needed way more blood than other times?

I'm wondering what would actually happen to a human if they just drank blood (like, it would not work out, but how *exactly* would that go down) and about vampire biology. Thanks. :)

Date: 2016-02-06 07:29 pm (UTC)
sinesofinsanity: For use when gorgeousness is appreciated (Bat beautiful)
From: [personal profile] sinesofinsanity
See poison would make sense, then the whole *I'm a murderer, woe is me* angst they have going on would be realistic, considering, even if you only bite one person a month, you're killing them either way, multiply that by however months in however many years an immortal vamp has lived and that's still a lot of dead people.

This also works with the anti-coagulant you mentioned earlier. People on strong blood-thinners (for heart/circulatory disorders) are told to be more careful if they happen to cut themselves, and if the heart condition develops to require surgery the nurses/surgeons need to be a lot more careful. If the anti-coagulant is particularly strong it can cause the person to bleed to dangerous levels or suffer other deadly reactions even if only veins are hit (anti-coagulants are a common molecule in both rat poison and a lot of snake venoms: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1533313/ and http://www.ncbi.nlm.nih.gov/pubmed/1360387

Can you mess up a pump by inducing too much suction?

Yes. It depends on the type of pump, but when determining the size of pump needed you need to include both pressure the outlet side and the inlet side. Probably a positive displacement pump http://www.engineeringtoolbox.com/positive-displacement-pumps-d_414.html is closest to what we're talking about here. Too much inlet pressure will mess up a positive displacement pump either by damaging the inlet or by overflowing the pump space or by overpressuring the pump to prevent pump stroke (unless there is a safety valve, which in this case is the blood going EVERYWHERE)


Can't that kill a person? Getting the wrong blood?
Yes. Your antibodies latch onto the antigens on donor blood cells and create clots.

Admittedly, it goes through a vampire's digestion first, so maybe that affects things.
Probably. I'm not sure, but I think cells get broken down by digestion so there'll be nothing to clot, but that's assuming that vampires digest rather than just straight using the blood as blood.

What's the difference between blood types?
https://www.youtube.com/watch?v=ttjn1jVACk8

Also I haven't even thought about possible disease transmission.
This again depends on how vampire digestion works. But I have read a couple of stories where a vampire refuses to drink from a person if they have a blood bourne disease like HIV or malaria.
Edited Date: 2016-02-06 07:36 pm (UTC)

Date: 2016-02-04 05:03 pm (UTC)
summerstorm: (Default)
From: [personal profile] summerstorm
I love that this randomly popped up on my DW circle. Love it.

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