Frozen body: Can we return from the dead?

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.

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.

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.”

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