Freezing Humans (Cryonics)

[Dan6541]

For anyone who's unsure Cryonics is the freezing of humans or animals for preservation, to be "woken up" at a later stage, as the title sugests.

 

It's an idea that has been used in science fiction while the heroes go on the adventure to other planets. Currently, people pay huge amounts of money for it in the hope they will be woken up some time in the future, when technology has advanced.

 

Around the world 200 people have undergone the cryopreservation procedure.

Cryonic procedures usually begin a few minutes after cardiac arrest, and cryoprotectants are used to drastically reduce the formation of ice. In some cryonics procedures these cryoprotectants are used in high concentrations. This allows tissues to cool and solidify without freezing, and is called vitrification.

 

The idea behind the freezing is that memory, personality and identity are stored in structures that don't need continuous brain activity to survive.

 

The big problem is that there isn't current technology that can reverse the freezing. Technology would be needed to repair damage from lack of oxygen being pumped to tissues while the patient is undergoing freezing (the patient has to be declared dead before the process starts so the tissues are without oxygen for at least a few minutes). Technology would also be needed to repair the damage done by thermal stress, the toxicity of the cryoprotectants and the freezing of tissues that don't successfully vitrify. Futhermore, the technology would need to reverse the patients death (usually cardiac arrest).

 

My question is, do you think we can ever expect these technologies to be invented?

 

If so, how long do you think it will take before they are invented?

[Mr Skeptic]

Well, we're continuously making progress in this field. For example, we can now freeze and defrost mammalian tissue such as mouse ovaries. Doing it with a human is more difficult, largely due to size differences. For example, small things can easily stretch a little as they freeze, whereas a human might crack. Then there is the problem that cryonics are mostly done on humans who are already dead, so that as well as defrosting them they need to be fixed. And even if it could be done right now it would take decades of testing to assess whether there was other damage resulting from the process.

[lsparrish]

Well as I see it there are three general technical routes for recovery:

 

1. 
    
   
2. You get preserved good enough that advanced biotech is plenty good enough. Regrowing a body below the neck could probably be done all with "wet" nanotech i.e. bioengineering. Organs would be replaced with "printed" ones, stem cells would fill in the cracks and gaps in the neural tissues, cryoprotectants would get sponged out the moment you start to devitrify to minimize toxicity, ischemic cascading effects would be halted with specially designed enzymes, etc.
   
3. It could be you don't have to be preserved quite that well even, if "dry" nanotech turns out to be feasible at some point. (Think 300 years in the future, not 20 minutes into the future -- there are huge technical barriers to this kind of technology compared to biology, which already exists.) Cells could be repaired in place while still frozen in liquid nitrogen under a vacuum, slowly progressing over weeks (or years) until you have a healthy body to thaw out.
   
4. Scanning brain pattens into a computer and running you as a simulated being might eventually turn out to be possible. The essential information processing power of neurons would need to be replicated, either digitally or by some kind of analog device. Then you would make use of an extremely sophisticated electron microscope or fMRI to make a detailed map of the brain. This could happen while you are in LN2, or you could be fixed using some future equivalent of formaldehyde and warmed back up. Some kinds of scan might be destructive of the original tissue whereas others might not be.
    
   

 

Whatever mechanism is used, while we may hope for it to be soon, it could be thousands of years in the future. It all depends how quickly science progresses in the various areas and what turns out to be physically possible. Younger people like me can hope that vitrification will get better and better over the course of our lifetimes. Perhaps we will reach a point of perfect brain preservation.