Cryonics is the low-temperature preservation of humans and animals who can no longer be sustained by contemporary medicine, with the hope that resuscitation may be possible in the future.It is proposed that cryopreserved people might someday be recovered by using highly advanced future technology. The stated rationale for cryonics is that people who are considered dead by current legal or medical definitions may not necessarily be dead according to the more stringent information-theoretic definition of death. Cryonics procedures ideally begin within minutes of cardiac arrest, and use cryoprotectants to prevent ice formation during cryopreservation.
Premises of cryonics:
A central premise of cryonics is that memory, personality, and identity are stored in durable cell structures and patterns within the brain that do not require continuous brain activity to survive. it is known that under certain conditions the brain can stop functioning and still later recover with retention of long-term memory. current cryonics procedures can preserve the anatomical basis of mind, and that this may be sufficient to prevent information-theoretic death until future repairs might be possible.
Obstacles to success:
Long-term cryopreservation can be achieved by cooling to near 77.15 Kelvin, the boiling point of liquid nitrogen. It is a common mistaken belief that cells will lyse (burst) due to the formation of ice crystals within the cell, but this only occurs if the freezing rate exceeds the osmotic loss of water to the extracellular space.Vitrification in cryonics is different than vitrification in mainstream cryobiology because vitrification in cryonics is not reversible with current technology.
Ischemia means inadequate or absent blood circulation that deprives tissue of oxygen and nutrients. At least several minutes of ischemia is a typical part of cryonics because of the common legal requirement that cryonics procedures do not begin until after blood circulation stops.The aim is to keep tissues alive after legal death by analogy to conventional medical procedures in which viable organs and tissues are obtained for transplant from legally deceased donors.
Neuropreservation is cryopreservation of the brain, often within the head, with surgical removal and disposal (usually cremation) of the rest of the body.
Costs of cryonics vary greatly, ranging from $28,000 for cryopreservation by the Cryonics Institute, to $155,000 for whole body cryopreservation for the American Cryonics Society's most expensive plan.
Philosophical and ethical considerations:
Cryonics is based on a view of dying as a process that can be stopped in the minutes, and perhaps hours, following clinical death. If death is not an event that happens suddenly when the heart stops, this raises philosophical questions about what exactly death is. Ethical and theological opinions of cryonics tend to pivot on the issue of whether cryonics is regarded as interment or medicine. If cryonics is interment, then religious beliefs about death and afterlife may come into consideration. Resuscitation may be deemed impossible by those with religious beliefs because the soul is gone, and according to most religions only God can resurrect the dead.
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