cryoprotectant

The problem is that we don't have a cryoprotectant that is sufficiently non-toxic and we can't freeze anything as big as a human quickly enough.

Second, the far larger problem is removing the toxic cryoprotectant once metabolic activity has resumed during thawing.

Brains are easier to perfuse with cryoprotectant than kidneys, so they tend to be preserved better.

Autopsy showed some areas where the cryoprotectant hadn't reached, so the kidney wasn't perfectly healthy.

We have a pretty good idea how to do hibernation: Saturate the tissue with some cryoprotectant and freeze it very quickly.

For cells in liquid media, you have about a 30 minute time window to remove the cryoprotectant before your cells are kaput.

They then start perfusion (replacement of blood with cryoprotectant), normally in the field.

The thing I don't understand is how circulating cryoprotectant chemicals through the brain doesn't destroy the tissue.

Scanning technologies have been used to show that cryopreservation via vitrification of cryoprotectant-infused tissue does indeed preserve the fine structure of brain cell connections.

I don't discount the other serious challenges of cryonics, like fracturing and cryoprotectant toxicity.

For cells in a liquid media solution, you can pellet cells to the bottom of a test tube in a centrifuge, then suction off the cryoprotectant.

For an entire living creature, I don't even know where you'd begin, or how you'd guarantee all the cryoprotectant was flushed out.

Proponents of this sort of thing would say the "cryoprotectant" chemicals vitrify, so the massive small scale trauma from ice crystal formation is prevented.

The emergency medical procedure was to dump the lower-ranking dead body already in the portable body freezer, exsanguinate the corpse by opening the carotid arteries, and pump the circulatory system full of "cryoprotectant fluid".