Blood loss

[Jason Rees]

Increase of blood pressure and a lack of circulation , so In your opinion it still is the starvation that causes unconciousness ?

Interesting

It's not an opinion. It's medically backed fact. Whether the cause is from lack of blood, lack of oxygen in the blood, or the presence of toxins in the blood; if the brain doesn't get oxygen (and sugar, as was mentioned), it won't function. You will fall unconcious.

If pilots pull neg-Gs, it can cause hemmorrhage (bleeding) in the eyes, nose, and even the brain, but it's going to be lack of oxygen in the blood that will take them out, not increase in pressure. Same with blood chokes (lack of oxygen in the blood), a diabetic attack (lack of sugar in this case), or even a CVA (stroke = lack of blood + oxygen to a portion of the brain).

"Air goes in and out, blood goes around and around. Anything else is bad juju." - Common EMT instructor phrase

[Stryke]

It's not an opinion. It's medically backed fact. Whether the cause is from lack of blood, lack of oxygen in the blood, or the presence of toxins in the blood; if the brain doesn't get oxygen (and sugar, as was mentioned), it won't function. You will fall unconcious.

Good , thats what I was after , not the opinion bit , but the medically based fact bit , It`s easy to assume why and always better to clarify , theres so much myth better to pass on fact .

If anyone has any references or studies on a blood choke to how it works even better .

[IJ]

"If pilots pull neg-Gs, it can cause hemmorrhage (bleeding) in the eyes, nose, and even the brain, but it's going to be lack of oxygen in the blood that will take them out, not increase in pressure. Same with blood chokes (lack of oxygen in the blood), a diabetic attack (lack of sugar in this case), or even a CVA (stroke = lack of blood + oxygen to a portion of the brain)."

Just to clarify a little, the high pressure in neg G's prevents inflow just like a choke. Positive Gs reduce inflow because the artery-vein flow gradient is overwhelmed by the G's; the blood pressure is low and insufficient flow results. A diabetic attack here refers to a hypoglycemic event, which can cause seizure, confusion, coma, or death. Diabetes that's not medicated causes hyperglycemia, which can cause confusion, if it leads to dehydration and other metabolic problems. CVA should not cause confusion or passing out unless its massive or the remaining brain wasn't in good shape to begin with. Half a brain is fine for cognition, usually personality, etc; you'll just be half paralyzed. And half is what you get if you completely shut down a carotid; it's hard to cause a larger stroke unless you stop blood flow long enough, which can infarct lots of brain, although you don't usually get a passing out, unless the cause is a big sudden event from the primary insult, eg, your heart stops.

"If anyone has any references or studies on a blood choke to how it works even better."

There isn't much more to say about it.... no blood out, no blood in; no blood in, oxygen runs out; oxygen runs out, unconscious.

[Stryke]

Thanks Ian , The Pressure build up stops fresh blood flow which causes the oxygen depletion hence unconciousness .

[Bruise Lee]

There isn't much more to say about it.... no blood out, no blood in; no blood in, oxygen runs out; oxygen runs out, unconscious.

I wonder about subclavian steal. In this case, due to blocked subclavian artery a vertbral artery can act like a vein and drain blood away from the brain. I wonder why the vertebral arteries cannot do something like that in an acute situation?

Also I have seen patients severely hypoxic functioning as though little was wrong - again the body can adapt to chronic conditions over time, but not acutely. I wonder if you can train for blood loss and reduced blood flow - an ability to function another minute or so in a state of severe acidosis, hypoxia and hypoperfusion. As sick as it sounds it kind of sounds like fun training -

[IJ]

http://www.tafm.org.tw/Data/011/128/120405.htm

There's a pic for subclavian steal. Instead of going north, blood coming up one verebral goes down the other because there's less resistance downhill into the subclavian artery and inadequate flow coming from the usual blood supply from the aorta.

There's no reason that would happen acutely with G's or a choke, or transiently. It's usually due to plaque buildup or compression from a funny rib, rarely a tumor pressing, and its rare in any case.

"Also I have seen patients severely hypoxic functioning as though little was wrong - again the body can adapt to chronic conditions over time, but not acutely."

This isn't so much an issue of adaptation as it is oxygen requirement and content. You require oxygen to your brain, continuously--and a lot of it. However, there's usually plenty of reserve, thru 1) more than necessary blood flow and 2) more oxygen content in the arterial blood than is necessary. Usually blood is 98% oxygenated or so, and if you look at the venous blood saturation, they're generally >70% so only 30% of supply was extracted. (That's a general consumption, on average I bet brain venous sat is lower than most veins because of the high metabolic rate; heart is also hungry).

So, if you reduce the blood flow, and the body simply extracts more of the oxygen from the blood it does get. Reduce the % oxygen saturation to the mid 80%s and you're usually fine because 80% saturation is still a lot of oxygen. If you only went from 98 to 78 when healthy, you can go from 88 to 68 when unhealthy. Brain doesn't use more oxygen when excited, just muscles, heart, etc, so hypoxia or poor perfusion is going to hurt physical more than mental performance initially. For these reasons we don't even give oxygen to lung patients until sats drop below 89% (for chronic use; in hospital, RN's like everyone >95% so they can worry less, but moral is, you walk around 89 from emphysema all day long and your doctor doesn't care).

In contrast, when you cease blood flow to the brain in a choke, you're going to use what you've got left in the head in seconds. Instead of constantly refreshing blood every 2 seconds you use 20% of the oxygen in, you get nothing new, so that oxygen content goes 100%, 80%, 60%, 40% over 8 seconds and that's goodnight (made up numbers, but more or less the story).

Are chronic lung patients adapted? Sure, usually with higher blood counts and some tolerance. Extraction increases, and some of the means to do that take time. But take someone used to 85%, make them 100%, put them in a choke, and they're down just as fast as a regular person.

"I wonder if you can train for blood loss and reduced blood flow - an ability to function another minute or so in a state of severe acidosis, hypoxia and hypoperfusion. As sick as it sounds it kind of sounds like fun training."

Sure, just bleed yourself out and run the marine obstacle course. I'll be sitting that one out. Patients who are sick enough to have poor perfusion are usually very unhappy or on their way out and I won't be joining them voluntarily.