[TazeTSchnitzel]

Has any living person ever had their heart intentionally stopped, been cryonically frozen, defrosted, and revived?

Because if not, then we don't know if it works on people who aren't yet dead. And if we can't do that, what hope do we have for reviving the actually dead?

(I'm aware in rare cases people have been massively cooled down and had their heart stopped for operations, but that's not quite the same.)

[ggreer]

Well... the whole idea behind cryonics is that the people preserved with current technology can be revived/reconstructed with future technology. Asking for a full preservation & resuscitation today is demanding evidence that wouldn't exist even in the case that cryonics works.

That said, there is evidence available today. 21st Century Medicine is a company that does research on cryoprotectants. Their chief science officer is Greg Fahy, who co-invented the first method for cryopreserving embryos[1].

21st Century Medicine's primary goal is to research new ways of cryopreserving tissues. This is already useful for research and some tissue banking (embryos, corneas, etc). If improvements continue, it could allow for organ banking. But the brain is an organ, and cryopreservation technologies work quite well on it. For example, 21st Century Medicine can take a slice of a rat's hippocampus, cryopreserve it, and thaw it. Afterwards, it's still viable tissue.[2] This is very important, as the hippocampus is not only crucial for memory consolidation, but it's the part of the brain most vulnerable to ischemic damage (especially the CA1 region).

21st Century Medicine has also experimented with whole organs. They've taken a kidney from a rabbit, cryopreserved it, thawed it, and transplanted it back into the rabbit. Then, after removing the remaining kidney, the vitrified-and-thawed kidney kept the rabbit alive indefinitely. Alcor uses the same cryoprotectants as this experiment.

If cryonics works, this is exactly the sort of evidence you'd expect to see today. Granted, it probably won't work, but the expected value is positive.

1. Ice-free cryopreservation of mouse embryos at −196 °C by vitrification (http://www.nature.com/nature/journal/v313/n6003/abs/313573a0...)

2. Cryopreservation of rat hippocampal slices by vitrification (http://www.21cm.com/pdfs/hippo_published.pdf)

3. Physical and biological aspects of renal vitrification (http://www.21cm.com/pdfs/12FahyORG5-3%5B1%5D.pdf)

[evanpw]

There absolutely no hope right now. The idea (for better or worse) is that there will be some scientific breakthrough in the future (e.g., nano-scale medical robots) that will make it possible to repair the damage done by the current, very crude, freezing technology. You're taking a gamble on future technology. My impression is that the typical person signing up for cryonics thinks that there's a small chance of success, but almost no downside if it fails (you're already dead).

[philjohn]

There's also some cases of people who's hearts had stopped after being caught outside in sub-zero temperatures being successfully revived with no adverse effects.

[qohen]

This isn't cryonics by any stretch, but doctors are seriously looking to put gunshot victims into suspended animation by drastically cooling them down so they can be worked on [0]:

When a shooting or stabbing victim goes into cardiac arrest due to massive bleeding, even the most heroic attempts at resuscitation fail 90 percent of the time. But a study to begin this month under the direction of Sam Tisherman and Patrick Kochanek at the University of Pittsburgh Medical Center Presbyterian Hospital will see if there's a better way: cooling the body after the heart has stopped beating, to the point where all other functioning virtually ceases as well.

By putting patients literally into a state of suspended animation—or "emergency preservation," as Tisherman calls it—the surgeons intend to preserve brain functioning long enough to close wounds that would otherwise be fatal.

[0] http://news.nationalgeographic.com/news/2014/04/140402-suspe...

[therein]

As far as I know nobody went through the cryogenic preservation process before they were declared dead due to legal reasons. It is a shame really. I hope at one point, somewhere in a country with less regulations, that will be done as well. Similar to the first heart transplantation.

[tptacek]

No.

[pen2l]

Which question was that a 'no' to? (there were two questions in the post you're replying to)

[TazeTSchnitzel]

Presumably the first.