At the moment cryonics is the only real hope to live forever for people beyond help by today's medicine.
Bodies can be preserved for decades or centuries until a future medical technology can restore those people to full health.
And unless we discover the cure against aging and dying in the near future, cryonics remains the best shot we have at immortality.
Cryonics was first proposed in 1962 by Robert Ettinger, a physics professor at Michigan University, in a book called The Prospect of Immortality, which argued that death could be a reversible process. In 1976, Ettinger, who by then strongly believed that cryonics is the key to preserve the human body, founded the Cryonics Institute in Michigan . The first person to give cryonics a try was James Bedford, a psychology professor who died of cancer in 1967. Others slowly began to follow, and as of 2014, about 250 bodies were cryopreserved in the USA alone, and 1500 people had made arrangements for cryopreservation after their legal death .
Cryonics involves cooling a recently deceased person to extremely cold temperatures in order to keep the body preserved until future science is able to repair or replace vital tissues and ultimately revive the patient . However, cryonics is much more than just the science of "freezing". It is not enough to just freeze patients into liquid nitrogen, because the water inside their cells would freeze as well. When water freezes, it expands and causes the cells to simply shatter. Moreover, at extremely low temperature ice crystals can form and seriously damage the cells. This would compromise the body at cellular level and hence the possibility to keep tissues intact once the person is resurrected. Therefore, the first step in the cryopreservation process is to remove the water from the cells and replace it with cryoprotectant or so called "human antifreeze". Once the water is replaced with the cryoprotectant, the body is cooled on a bed of dry ice until it reaches -130 °C. The next step is to insert the body into an individual container that is then placed into a large metal tank filled with liquid nitrogen at a temperature of around -196 °C .
If current technology helped us develop rather safe protocols for cryonics, in the past things didn't go as smoothly as today. Of seventeen documented freezings through the 70's, all but one ended in failure. Not using cryoprotectants but only straight freezing to liquid nitrogen temperature, incorrect storage temperature, technical failures of the storage capsules, are a clear example of the mistakes made in the early days of cryonics . A middle-aged woman from the Los Angeles area, was placed in liquid nitrogen, two months after being embalmed and stored at slightly above-freezing temperature in a mortuary refrigerator. As expected, the questionable procedures compromised the entire process . Nowadays, similar failures are unlikely due to improved and safe methodologies, strict regulations, and more advanced technology at our disposal, therefore patients now have a better chance at resurrection.
There are two advances that helped cryonics research move further: the vitrification process and the emerging science of nanotechnology, that will eventually lead to devices capable of extensive tissue repair and regeneration . Vitrification prevents tissue damage by replacing the blood with a mixture of antifreeze-like chemicals and an organ preservation solution. As for nanotechnology, scientists strongly believe that future progress in nanomedicine could recover any preserved person in which the basic brain function has been retained [6,7].
Still, while going through this procedure there are some risks, most of them being associated with the phenomenon called reperfusion injury. This is an injury that occurs when the blood flow is restarted after the heart stops. Due to inflammation, oxygen-carrying blood is prevented from reaching the brain, hence the brain cells die over a period of hours. Assuming that a patient is in a remote location, and fails to be transported in time to the cryonic facility, his brain might not be viable anymore upon resuscitation . However, living neurons have been successfully cultured from brains after 8 hours of cardiac arrest. Therefore, scientist think that in the future we might be able to preserve the brain function even in extreme cases like this .
One of the biggest challenges when it comes to successful resurrection is the thawing or rewarming process. Unless the rewarming occurs rapidly and uniformly, cracks will appear in the tissue and destroy cellular structures. However, during the past decade our knowledge of cryonics and procedures have advanced far beyond imagined by most experts. Even though people in cryonic suspension haven't yet been revived, it will be a just a matter of time, as intensive research is conducted for this purpose. Living organisms can be brought back from a dead or near-dead state through defibrillation and CPR, neurosurgeons can cool patients' bodies so they can operate on aneurysms without damaging or rupturing them, frozen human embryos can be successfully defrosted and implanted in a mother's uterus and grow into perfectly normal human beings. Dogs and monkeys have been revived after having their blood replaced with anti-freeze and cooled to below 0 °C , nematode worms have been preserved at -196 °C and revived while maintaining their long-term memory , and a rabbit kidney was frozen at -135 °C and successfully transplanted to another animal . Moreover, there is proof that vitrification can maintain viability and structure of brain, in rats . Scientists have recently succeeded to cryogenically freeze and rewarm sections of heart tissue, without damaging their integrity and they believe this could pave the way for organs to be stored for months or years. If the technique could be scaled-up, it's safe to assume that reanimation of a human body could be achieved in the future .
According to Cryonics Institute president Ben Best, cryonics revival can be compared to a "last in, first out" process. With science evolving at such a fast pace, people cryopreserved in the future, with better technology (that causes less damage to the tissue), may require less advanced technology to be revived. Preservation methods would eventually get better until they are demonstrably reversible, after which medicine would begin to reach back and revive people cryopreserved by more primitive methods . Nanotechnology (which holds the promise of future biological repair) is already a major industry, making the promise of revival more apparent and more exciting.
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