[cyberax]

One thing to keep in mind, is that if somebody is hypothermic and not just frostbitten, then rapid re-warming is a bad idea.

Body protects itself by shutting down blood flow to skin and extremities, keeping the core warm. So if the extremities are rapidly re-warmed, then blood vessels in them dilate. And then blood starts flowing through oxygen-depleted tissues that are cold and full of accumulated metabolic waste.

Not a good combination, and you might end up with organ damage as a result.

Gradual re-warming instead gives the body time to slowly clear the waste as blood flow re-establishes itself.

[Etheryte]

This is interesting, I was taught that instead of the metabolic waste, the issue was the cold blood from extremities quickly cooling down the internals once allowed to circulate freely. Do you have any references for this?

[Interloper2099]

Reperfusion injury can occur after a crush injury. The myoglobin, creatine, potassium and phosphorus from destroyed muscle cells cause kidney damage. The potassium is really important as it is supposed to stay locked within cells and high levels can cause arrhythmias. For more info look up crush syndrome and reperfusion injury. This is all slightly different from hypothermia but may share some pathways if cells are destroyed.

[dotancohen]

What it's worth, we were taught the same thing about people crushed under e.g. rubble in combat medic training 20 years ago. And the same consideration applies to removing a tourniquet that had been in place for over two hours as well.

[xelamonster]

So what does that actually look like in practice, lifting the piece of rubble an inch at a time? How slowly would you release a tourniquet in that situation?

[cperciva]

I'm not a medical doctor, but my understanding is that in the scenario of "patient's limb has been trapped/crushed for an extended period and can now be freed" you're supposed to tourniquet off the limb before freeing it.

This helps both for delaying reperfusion issues until the patient can be in the hospital with IV lines in place, and also in case there's an injury which could cause massive blood loss (since a trapped limb is inherently one which is hard to inspect for injuries).

[xelamonster]

Makes sense, thanks! I first heard about crush syndrome from an episode of House, and IIRC it ended up being a cause of death so didn't exactly learn how to manage it. Though I want to say the woman there was pinned from the waist down, which I'd imagine complicates things.

[dotancohen]

Yes, this is correct.

[cyberax]

That was a part of my training for snow rescues. It's probably a combination of both.