[tapland]

Because it's hard. I helped out at a company among many that are trying to develop a system that would allow you to do this in ambulance and they started testing prototypes 10 years ago and have yet to progress from that stage.

[JshWright]

It's not that hard... you just throw some ice packs in the groin and armpits. You won't get them fully into the TTM range in a 20 minute transport, but you can start the process.

[tapland]

That is extremely ineffective.

What you might want to do is to cool the brain through cooling the outside of the head as well as through the nasal cavity.

Even if you chug a giant slurpee the largest effect on the brain temperature will be the cooling of the nasal cavity on it's way down.

[JshWright]

Packing with ice packs is a standard component of TTM, generally in conjunction with other therapies (chilled IV fluids, etc). It's also the easiest step to take in a prehospital setting, which is why we do (this is a thing I've done with maybe a dozen patients over the past few years). I'm not just making this stuff up, it's based on actual treatment protocols and algorithms.

We're talking about a naked, sedated patient (so they're already losing a lot of heat due to simple convection, and there's no heat being generated by skeletal muscle movements). The body's metabolism has slowed significantly, and it's producing anywhere near the normal level of "baseline" heat.

[tapland]

Do you have any links to data showing effects on brain temperature from that treatment?

Afaik interest has been low in carrying around enough ice pack capacity to make this viable, and with lacking data for it even working, whereas head-cooling packs with circulating liquid through a cooler takes little space, cools way more efficiently and required no other maintenance after insertion into the patient in the ambulance (and is moved with the patient while continously working).

[JshWright]

Overcooling is more of a risk with I've packs than not cooling enough. It's much less of a concern in a prehospital setting though, since we're not with the patient that long. It's more of an issue in the ICU.

https://www.ncbi.nlm.nih.gov/pubmed/17114983

[dsfyu404ed]

Sticking ice in proximity to major arteries is going to be a lot less effective without a beating heart to circulate all that newly cold blood.

[JshWright]

This procedure is initiated after the heart has been restarted[1]. You're absolutely correct that it's pointless to do it earlier, especially since the far more important thing is getting the heart beating again.

[1] This is known as "targeted temperature management" (TTM), and is part of the standard post-ROSC (return of spontaneous circulation) algorithm in ACLS (Advanced Cardiac Life Support), if you're looking for terms to Google.

[agumonkey]

the cold won't distribute at all ?

[dsfyu404ed]

It will but much more slowly. Think of cooling the blood as using the surface area of the arteries and veins as a heat sink to cool the body. Without that blood moving your next best heat sink is the skin so start piling on the ice.

[JshWright]

The body itself is the heat sink. The skin is a radiator. The blood is the liquid in a liquid cooling system (moving heat from the sink to the radiator). To your point, liquid cooling systems become _much_ less effective when the liquid stops pumping.

[agumonkey]

So I guess ice and cardiac massaging are synergic.

[t0mbstone]

Sounds like a good way to introduce frostbite

[JshWright]

Those spots are not prone to frostbite, since the "coldness" gets distributed through the rest of the body very quickly (apologies for playing a little fast and loose with thermodynamics there). This is why they're used in the first place to cool the person quickly.

[meowface]

I don't know the exact implications, but I'd probably rather have frostbite or even lose a limb than have serious permanent brain damage.

[sho_hn]

Can you talk about the problems involved?