Cryonics is the low-temperature preservation of humans and animals after death. Proponents of cryonics believe that what we consider legal death is really just an excuse for the medical community to give up on saving sick people. It is certainly true that death is a bit difficult to define by medical standards. It’s not terribly uncommon for hearts to stop and then start up again, or for brains to go dead, but hearts to go on a-beating indefinitely. Thus, figuring out exactly when a person is really dead is tough. After all, most of the time when a person is declared legally dead, nearly all of their cells are still living. For these reasons, hundreds of people have decided that the best thing to do is to have their bodies frozen immediately after their legal death, in the hopes that the technology to revive them and then heal them will someday be available.
The central premise of cryonics is that memory, personality, and identity are stored in the cellular structures and chemistry of the brain. Proponents claim preservation of this information is sufficient to prevent information-theoretic death until future repairs might be possible. Information-Theoretic Death is a counter-point to Legal Death. It is the destruction of the human brain (or any cognitive structure capable of constituting a person) and the information within it to such an extent that recovery of the original person is theoretically impossible. The concept of information-theoretic death arose in the 1990s in response to the problem that as medical technology advances, conditions previously considered to be death, such as cardiac arrest, become reversible and are no longer considered to be death.
There are three primary obstacles to cryopreservation at this time. The first is preservation injury. Though the preservation process is intended as a life-saving procedure, there are side effects. Damage from freezing can be serious; ice may form between cells, causing mechanical and chemical damage. Cryoprotectant solutions are circulated through blood vessels to remove and replace water inside cells with chemicals that prevent freezing. This can reduce damage greatly, but freezing of whole people still causes injuries that are not reversible with present technology. In addition to damage from freezing, further damage can be caused by ischemia, lack of oxygen-rich blood circulating in the body for the period of time before the preservation process can begin. Several cryonics organizations now utilize standby-teams who are on hand to begin the process of preservation as soon as possible after the heart stops. For legal (and ethical?) reasons, it is not permissible to begin the cryonics process before legal death has been declared.
The final—and perhaps most disconcerting—obstacle to cryonics is that we don’t currently have the technology for successful revival. Revival requires repairing damage from lack of oxygen, cryoprotectant toxicity, thermal stress (fracturing), freezing in tissues that do not successfully vitrify, and reversing the effects that caused the patient's death. In many cases extensive tissue regeneration will be necessary.
It has often been written that cryonics revival will be a last-in-first-out process. In this view, preservation methods will get progressively better until eventually they are demonstrably reversible, after which medicine will begin to reach back and revive people cryopreserved by more primitive methods. Revival of people cryopreserved by the current practices may require centuries, if it is possible at all. Survival would then depend on whether preserved brain information was sufficient to permit restoration of all or part of the personal identity of the original person.
The cryonics field seems to have largely consolidated around three non-profit groups, Alcor, Cryonics Institute, and the American Cryonics Society. These are the folks you need to talk to if you want to pursue cryonics for yourself. Costs vary greatly, ranging from $28,000 to $155,000. To some extent these cost differences reflect variations in how fees are quoted. Some organizations don’t include “standby” (a team that begins procedures at bedside), transportation costs, or funeral director expenses in the quoted price, which must be purchased as extras.
While cryonics is sometimes suspected of being greatly profitable, the high expenses of doing cryonics are well documented. The expenses are comparable to major transplant surgeries. The largest single expense, especially for whole body cases, is the money that must be set aside to generate interest to pay for maintenance in perpetuity.
The most common method of paying for cryonics is life insurance, which spreads the cost over many years. Cryonics advocates are quick to point out that such insurance is especially affordable for young people. It has been claimed that cryonics is affordable for the vast majority of people in the industrialized world who really want it and plan for it in advance.