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Comment by ajdude | Hacker News Reader

From what I remember reading when I was looking into this along time ago, the issue is managing to freeze and later thaw everything quickly enough so cell damage does not occur.

Due to physical constraints, one can freeze a mouse or a rat kidney and bring it back with less damage except the same does not apply to a human. It's just not possible with present technology to get everything frozen quickly enough.

I'm very interested if this new copper nano magnetic field solution will scale.

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Tom Scott made a great video about it, he even got to the guy who started using microwaves for thawing entire small animals. Before microwaves (diathermic heating) they would use a hot piece of metal, like a large spoon.

https://youtu.be/2tdiKTSdE9Y

And yes, you can unfreeze a rock solid rat, then see it walk around. This is why cryogenics was hyped so much, because it sort of works on small animals.

Maybe one could build an apparatus made of a bunch of narrow expanding tubes that pierced the organ without really damaging it then carried coolant to freeze the organ quickly. Could heat it back up quickly via frozen-in-place the tubes as well. Wonder if this has been attempted before

Good news! Your organs are already irrigated by your circulatory system

What do you reckon, tamper with the existing fluid, maybe add some heat pipes into the existing large passageways? Not sure if they have the right shape for the kind of temperature change being discussed.

The other thing would be how to remove this later on and not kill whoever got the transplant with this infusion.

That part I imagine would probably be the easy bit - just wash it out.

Or do you mean the perforated version? I like that idea but needles so small that they don't cause significant damage does seem at cross purposes with heat wicking needles.

Thinking of something like this?

https://www.pfizer.com/news/articles/nature’s-antifreeze-hol...

Yessir!

But doesn't the loop-back happens in capillaries - which are biologically mediated?

Totally outside my area of expertise, but I wouldn't expect you can pump cold fluid into arteries and it'll just come gushing out the veins

I would love an answer to this question

I found this video https://www.youtube.com/watch?v=6ecmOuCIoNc which makes me thing that pumping cold fluids would work at least a bit.

I thought of this too but the high throughput of fluid to get fast cooling would require a pressure so high it would destroy the organ. Running micro tubes through the capillaries would require significant advances in materials science.

I assume volume is the problem. Can anyone explain what the speeds are required to freeze any particular organ safely?

I imagine freezing is the less problematic side. You can probably dump it in liquid nitrogen (exaggeration, but you get my point). But you can't heat it fast (enough) because the extreme heat would burn/vaporize the exterior while the inside is still cold.

I'm not sure about what's the problem with slow thawing though: AFAIK most tissues are pretty stable at fridge temperature for a few hours (from 4hours for a heart, up to 36hours for a kidney), but freezing is another matter: the slower you freeze things, the bigger the ice crystal grow, and IIRC you need to freeze things very quickly if you don't want damages from the ice crystal (you want to “vitrify” the water, instead of crystalizing it) and I don't think even liquide nitrogen is enough to freeze big organs quickly enough.

There are some tricks with cryoprotectants and rarely used cryopreserving protein, but triggering that and not damaging cells is an active field of research.

I remember there being research where they successfully froze and then revived hamsters in the microwave (a scientific one to prevent uneven heating though), but it had no hope of working in people or even cats and dogs.

This is partly true

https://www.thestar.com.my/news/true-or-not/2021/12/30/quick...

Nowadays we have much better tech for rewarming frozen animals.

Afaik the problem isn't the rewarming, but the quick and even freezing.

A scientific hamster? :P

ah yes, the well known "hot pocket" problem - one of the most challenging in cryogenics

There has to be a trick to cooling something fast enough then freezing it. People falling into freezing water, dying, then being revived ours later comes to mind. I do suppose actually freezing is very different but who knows, maybe there could be a connection?

The body has time to prepare for the cold by making a lot of cryoprotectants in the cells. That of course only works in quite particular conditions and in a liivng host, and the induction would be quite painful. The remaining damage of defrost is fixed later on.

> People falling into freezing water, dying, then being revived ours later comes to mind.

Except this doesn't exist, these people don't actually freeze, as in they never go bellow 0, most of them stay well above 0 actually. They're very different phenomenons

For example: https://jmedicalcasereports.biomedcentral.com/articles/10.11...

> A 52-year-old Italian mountaineer, was trapped in a crevasse and rescued approximately 7 hours later by a professional rescue team.... His core temperature was 26.0 °C

or: https://en.wikipedia.org/wiki/Anna_Bågenholm

> her body temperature decreased to 13.7 °C (56.7 °F), one of the lowest survived body temperatures ever recorded in a human with accidental hypothermia.

>> People falling into freezing water, dying, then being revived ours later comes to mind.

> Except this doesn't exist, these people don't actually freeze, as in they never go bellow 0, most of them stay well above 0 actually. They're very different phenomenons

Yep, I stated that as well.

> Afterward, they cool it quickly — 24 degrees Celsius per minute — to bypass the formation of cell-shredding ice crystals and directly enter a glass-like state.

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