The idea of preserving a person’s body at very low temperatures in the hope that it will be restored by future medical technology has been a staple of science fiction. But could cryonics be a genuine way of being brought back to life, years into the future?
What is the cryonic process?
When a person has been declared legally dead, the cryonic preservation company is informed and it dispatches a response team to attempt to keep the person’s blood pumping around their body. The body is packed in ice and injected with various chemicals in an attempt to reduce blood clotting and damage to the brain.
Once the body reaches the cryonics facility it is cooled to just above water’s freezing point and the blood is removed and replaced with organ preservation solution. The body’s blood vessels are injected with a cryoprotectant solution to try to stop ice crystal formation in the organs and tissues and the corpse is cooled to -130C. The final step is to place the body into a container which is lowered into a tank of liquid nitrogen, kept at -196C.
Latest figures reveal that around 150 people have had their whole body stored in liquid nitrogen in the United States, while 80 have had just their heads or brains preserved. However, there are more than 1,000 living people who have instructed companies to preserve their bodies after their death.
Why do some people think it might work?
Cryonic preservation enthusiasts say there are three reasons to be hopeful. Firstly, despite an organisation being required to wait for a patient to be declared legally dead before they can be frozen, they claim that damage to the brain can be reduced by ensuring oxygen levels are maintained.
Secondly, cooling a body to a low enough temperature slows chemical processes in cells and tissues sufficiently to prevent any further degradation of the body.
Finally, while damage is inevitably inflicted on the body from the cooling process and any illness or ageing they might have suffered, they hope that future nanotechnology may be able to repair this.
What problems have scientists identified?
If a person is cooled below -5C the water inside their cells freezes and creates ice crystals. As ice is less dense than liquid water, it takes up more space. So the crystals punch through the cell membranes causing severe damage.
Cryonic preservation facilities attempt to overcome this by employing a process known as vitrification. This replaces some of the body’s water with cryoprotectant agents, in an attempt to reduce the amount of ice crystal formation.
As yet there is no proof that we can vitrify human organs. Cryobiologist Dr Dayong Gao from the University of Washington, Seattle, said: “We know we can successfully vitrify very small things like insects and simple tissues like blood vessels. This is because the smaller size makes it easier to control cooling and cryoprotectants can be properly diffused.”
So how will the organs of cryonics patients be affected? Dr Gao said: “We simply don’t know if they’ve been damaged to the point where they’ve ‘died’ during vitrification because the subjects are now inside liquid nitrogen canisters.”
The outcome isn’t hopeful according to biochemist Prof Ken Storey, from Carleton University in Ottawa, Canada.
“We have many different organs and we know from research into preserving transplant organs that even if it were possible to successfully cryopreserve them, each would need to be cooled at a different rate and with a different mixture and concentration of cryoprotectants.
“Even if you only wanted to preserve the brain, it has dozens of different areas, which would need to be cryopreserved using different protocols.”
Could a human survive the thaw?
If scientists did one day work out how to successfully cryopreserve a whole human body, there is still the matter of bringing the body back to life.
Dr Gao said: “Even if you manage to limit the damage from cryoprotectants, the question remains of how they would be safely removed.”
There are other significant complications, such as the fact that cooling a body to -196C makes it incredibly brittle.
“The body could easily fracture like glass during warming due to thermal stress,” Dr Gao said.
He added that the brain, which has as many as 10,000 connections for each of the 100 billion neurones, is particularly sensitive to heating and cooling.
What’s the damage?
There is also the issue that bodies are likely not to be at the pinnacle of health, but at the end of life after illness and ageing have had their effect.
Cryonic preservation advocates say nanotechnology, which is the manipulation of matter at a molecular level, could one day provide a solution.
However, Prof Storey is extremely doubtful of this claim, because of the scale of the problems in each cell.
“A human cell has around 50,000 proteins and hundreds of millions of fat molecules that make up the membranes. Cryopreservation disrupts all of them,” he said.
A far more detailed understanding of how the brain works would also be critical in knowing what would need to be repaired.
Neuroscientist Dr Martin Ingvar from the Karolinska Institute in Stockholm said: “The subtle properties of the brain network are uneven. Some of these connections are crucial whereas others could be lost – but we do not know which ones.”
Still, Dr Ingvar said a person’s identity could theoretically be retained in the future if scientists worked out how to overcome the destructive effects of cryopreservation.
“If that could be solved, there is no reason why (in theory) a cryonic procedure couldn’t preserve memories. However, it would be like time travel with a lot of confusion for the subject.”
An uncertain future
However you look at it, cryonics is a matter of hope and belief in the future. Broad statements crop up on all cryonic organisation websites stating that while “there are no guarantees” cryopreservation can work “technology is always improving”.
“People can always have hope that things will change in the future, but there is no scientific foundation supporting cryonics at this time,” Dr Gao said.