A short post on some basic research into Cryogenics and preservation of humans. Just wondering where the technology is upto and what we are currently capable of.
Cryonics
The science that studies the low-temperature preservation of animals and humans who cannot be sustained by
current medicine, in the hope that at a future date when medicine has advanced
they can be brought back and healed.
Cryopreservation
Cryopreservation of animals is not currently reversible. The rationale is that
people who are ‘dead’ by our current medical standards are not necessarily dead
by future standards. There is a lot of research currently going into this
field, and all kind of medical theories are being developed. The hope is that
if a creature is properly cryopreserved, in the future we will have the
technology to safely bring them back to a living state. Animals must be
preserved very carefully to ensure the body and brain are frozen in a
functional state, not one where the brain has been damaged due to oxygen
deprivation during the process for example.
Currently, approximately 270 people have been cryopreserved
and are awaiting technologies to be developed so they can be brought back in
the future. Think Phillip J. Fry from Futurama.
Cryonic advocates say that it is possible using current
technology to preserve the finer cell structures of the brain where memory and
identity reside. Long-term cryopreservation is achieved by cooling the animal
to approximately -196 degrees Celsius.
Water crystal formation and Vitrification
One issue with being frozen is that water within cells
expands as it turns into ice. This can cause cells to burst and cause serious
damage. This only happens if the subject cell is frozen faster than the rate at
which water can evacuate the cell into the intercellular space. One way to
avoid this is by using cryoprotectants. This is a fluid that is pumped into the
animals veins to replace water before the subject is frozen. The fluid does not
freeze and expand like water so damage to the cells is avoided.
Cooling and solidifying without ice crystal formation is
called Vitrification. Vitrification is used to bank transplantable organs, in a
reversible way. However, in Cryonics it is used to vitrify brain tissues in a
way that we cannot yet unvitrify from. Tests have been done to observe for any
structural damage from the process of vitrification and it was shown no
structural damage was inherent. The worry is toxicity from the cryoprotectant
fluid, but this is much easier to repair from than from structural damage from
crystallisation and formation of ice.
Ischemia
Ischemia refers to a state where tissues are deprived of
oxygen and nutrients, usually due to inadequate or absent blood circulation.
For example, loss of too much blood, or a heart attack. Currently, brain
rescuscitation is usually not possible after a traditional 4-6 minute period of
Ischemia. Our definition of Legal death is the moment the heart stops beating.
By Law, cryonic treatment is not legally allowed until the person is declared
legally dead. So there are usually a few minutes of Ischemia between the point
of Legal death and cryopreservation. The hope is that this can be reversed in
the future.
Death
Here is a very interesting concept to think about.
Definitions of death change as technology advances. The early stages of ‘death’
by todays definition is actually just a form of ischemic injury that will be
reversible in the future. One day we will reach a point where someones heart
stopping and their brain undergoing ischemic injury will in no way mean the
person is dead. Maybe it will just mean that it is time for their routine body
swap.
Revival from a Cryopreserved state
The main types of technology that will likely lead to
successful revival techniques are advanced bioengineering techniques, molecular
nanotechnology, nanomedicine, or mind uploading. All fields which are evolving
rapidly with current developments.
Revival involves a number of damages to be addressed:
· -Ischemic injury due to lack of oxygen
· -Cryoprotectant toxicity
· -Freezing in tissues that do not vitrify
· -Halting effects of whatever caused the patients
death in the first place
The most likely hypothetical scenario at this point in time
is repairs being carried out by vast numbers of microscopic organisms or
devices, popularly termed nanobots.
An interesting idea is that as time goes on, preservation
technology will improve. Therefore people preserved last, before revival is
possible will be preserved the best and would be the easiest to revive. The
people preserved first would have more damage done and would have to wait till
revival technology is improved. Last-in first-out.
Neuropreservation
Neuropreservation is cryopreservation of only the brain.
Often within the person head, with surgical removal and disposal of the rest of
the body. Often portrayed in popular culture as a head in a jar. The general
idea is that by the time technology evolves to the point of reviving
cryopreserved patients, surely we will have the technology for general tissue
regeneration. Some think the whole body might as well be preserved, and the
body discarded at a later date if not necessary. Others think the probability
of tissue regeneration being possible before cryogenic revival is extremely
likely.
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