Posted on Monday 9 May 2005
Continued from Cold Storage I
So you’ve done it.
Your heart is stopped. As far as the law and most of society is concerned, you are dead. But you are not gone… not yet anyway. Before you died, you had a number of long talks with your loved ones, arranged funding for cryosuspension, made all the legal arrangements to “donate your body” to whatever firm currently has you immersed in liquid nitrogen, and so forth. Will you really be coming back though?
This is a tricky question, and one I glossed over briefly in Cold Storage I. What it boils down to is this: What is death, really, and are you actually dead? To put it succinctly, death is the point at which your memories, personality, and sense of identity have degraded past the point at which any conceivable science (short of time travel) would be able to restore you to life. So, death is related to information.
It’s All About Information
Your brain contains quite a lot of information. It contains a huge number of neurons (about 100 billion) and each one of those neurons is connected to (on average) between one and ten thousand other neurons, and in some cases up to about one hundred thousand, for a total of about 100 trillion connections. The connections themselves are not “binary” in fashion (either on or off) - they each have a certain amount of strength. If you ever wanted to know the total possible number of states that the human brain could assume, it would be about 100 trillion squared times the number of possible distinct potential levels in a synapse. According to Carl Sagan, there are more possible brain-states than atoms in the entire universe. Pretty heavy, isn’t it!
Data Integrity and Recovery
Now, at the moment the heart stops, all of those 100 billion neurons and their 100 trillion connections are in peril. Without oxygen and nutrients, the brain will begin to degrade. Here are some question marks I’ve identified:
- What is the half-life of a synapse during warm ischemia? In other words, once blood flow stops, how long does the average synaptic connection take to turn into unrecoverable mush?
- To get more precise, what are the statistics on this, beyond just the average? How about the standard deviation? The distribution? Is it a bell curve or has it got two peaks or does it go all over the place like a seizmometer during an 8.0? Do the connections in the cerebellum tend to go faster? Or in the limbic system, or in the neocortex?
- Again, a question of statistics: If we cool down the brain by ten degrees, by how much do we slow the degeneration of the brain? And how much can we lose (and in which areas) before the person’s memory, personality, and individuality are harshly impacted? How much can a given brain compensate for this loss?
- What is the effect of glycol perfusion followed by vitrification? Will it randomly scramble the synapses, and if so, to what extent?
- How effective will nanorobots be at examining damaged neurons and synapses, forensically determining their correct (in-vivo) operating state, and restoring them to that state?
- If the person had some kind of brain disease or injury, such as Alzheimer’s or some other form of dementia, could nanorobots untangle that mess as well, and perhaps assist the brain’s natural ability to heal its white matter?
- Might it be necessary to bring the body up to operating temperature and run it on life support, and allow the brain to at least partially restart, so that the nanorobots could obtain more information about the neural network? What would the risks be in this?
Evidence of resiliency in the human brain
People have survived brain ischemia for periods lasting from several minutes to over half an hour. Whether a given person will survive seems primarily based on age. Young children have been immersed in icewater, and been pulled out “dead.” (Heartbeat flatlined, no brain activity.) But a few of those children have been revived and come back without appreciable brain damage. Of course, the resiliency of youth is widely known, and it seems probable that the young brain is able to repair damage more easily since it doesn’t have as many established neural connections to worry about. Any adult who has been in icewater for half an hour, and is pulled out without a heartbeat or brain activity, is not likely to be brought back with CPR alone.
Caveat Emptor
These are the kinds of questions that should be asked by brain-only patients. Full-body cryosuspension is naturally more complicated, since there are many organ systems beside the brain that may require extensive repairs. There may also be more damage since a full-body suspension cannot be perfused as thoroughly as a head-only suspension given a certain amount of time.
Broken China
No, not the Middle Kingdom. Dinner plates! You take a dinner plate and smash it. With enough time, patience, and super glue, you can get it back to its original state. Nanomachines would be able to do an extremely good job of that sort of task. With the brain, it’s a similar problem. There may be a perception among some that since adult brains can’t restart themselves after prolonged ischemia, they must be irretrievably damaged. That isn’t necessarily so. With nanotechnology, someone who’s been “iced” long enough for them to be “dead” and cold, might still be retrievable.
Why science is likely to develop cryo-resuscitation technology, regardless of “medical time travellers”
It seems probable that future scientists will be motivated to try to revive cryosuspended patients, once the technology is good enough. But what if that challenge alone isn’t enough to motivate a competent organization to develop this technology?
Even if nobody had ever bothered with cryosuspension, and no one does all the way up to the point at which nanotechnology becomes competent to revive such a patient, medical science will still have use for the ability to resuscitate people who have recently “died” (or who will soon.) I’ve already mentioned drowning victims. They alone are reason enough to develop brain-related nanotech. Another possibility is deliberate cryosuspension before the heart has stopped. Let’s say that someone manages to contract ebola, and the nanotech treatment for this requires three days to cure the patient. But let’s say that by the time the patient gets to a competent hospital, the infection is so advanced that he or she only has two days to live at most. The hospital could cryosuspend the patient (and the ebola infection along with them), and at that point, nanorobots would have all the time they needed to go in, destroy the infection, and repair the damaged organs. The suspended patient would then be revived, and wake up feeling perfectly fine.
So, even if no one cared enough to work on this technology for the sake of “medical time travellers,” there would still be plenty of motivation to develop it for the sake of those who will be alive when the technology is finally mature.
Last In, First Out
Cryopreservation techniques continue to improve. The first patients (from the 1960s) have quite a lot of ice damage. This may be difficult and perhaps even impossible to reverse. Since that time, the technique has improved. Someone suspended today will have a much more well-preserved biostructure than the older “time travellers.” Obviously, if there is much less ice damage, it will be all the easier to restore the patient. So the first people to come out of cold storage are likely to be the last who went into it, with progressively earlier cases being revived as the technology continues to improve. Someone preserved in, say, 2028, might be brought back in 2040, whereas someone preserved in 1968 might not be brought back until the 2060s.
In Cold Storage III, I will discuss a few scenarios for cryosuspended patients who are eventually restored to full life.