The two most popular technical arguments against human cryopreservation are that cryonics causes irreversible freezing damage and that the delay between pronouncement of legal death and the start of cryonics procedures causes irreversible injury to the brain. Such arguments can be countered by pointing out that freezing damage and prolonged periods of warm ischemia do not necessarily produce information-theoretic death. The argument that cryonics procedures themselves produce additional forms of injury which cannot be treated with contemporary technologies misses the point that cryonics involves stabilization of critically ill patients so that they can be treated with future technologies. In the case of freezing damage, this argument has also lost most of its value because today’s cryonics organizations employ vitrification agents to stabilize a patient at cryogenic temperatures without ice formation.

The criticism that delays between pronouncement of legal death and start of cryonics procedures will cause irreversible injury to the brain is also unfair because it treats the current social and legal obstacles to perform better stabilization of cryonics patients as an intrinsic element of cryonics itself. But cryonics does not necessarily involve cryopreservation of persons who have been pronounced legally dead. The current Wikipedia entry on cryonics defines cryonics as follows:

Cryonics is the low-temperature preservation of humans and other animals that can no longer be sustained by contemporary medicine until resuscitation may be possible in the future.

As can be deduced from this definition, cryonics constitutes a form of medical time travel that uses cryogenic temperatures to allow a terminally ill patient to reach a time when more advanced treatments may be available. As such, it would be premature to declare a cryonics patient “dead.” In most cases, pronouncing a person dead only reflects our current inability to treat the patient and our psychological need for definitive answers to questions of life and death. The limitation that cryonics procedures can only be started after pronouncement of legal death reflects the unfortunate fact that the current medical establishment does not recognize cryonics as a credible form of advanced critical care.

As a result, cryonics is currently practiced as a form of emergency medicine in which conventional resuscitation technologies such as chest compressions and ventilations are used to avoid the kinds of injury that follow after cardiac arrest. Although there will always be a place for cryonics as a form of emergency medicine to treat cases of trauma and  sudden circulatory arrest, most patients who currently present for human cryopreservation would benefit from more hospital cooperation in choosing cryonics as an elective medical procedure.

Although current cryonics organizations such as Alcor try to make the best of a bad situation by employing standby teams that allow rapid intervention after cardiac arrest to reduce brain injury, much improved quality of care of cryonics patients would be possible if cryonics procedures would start at a point where medical professionals (with informed consent of the patient and/or family) would determine that further treatment of the patient with contemporary technologies would be futile, or even counter-productive.

When this determination is made, conventional life support for the patient would be terminated and deep hypothermia would be induced using cardiopulmonary bypass. At deep hypothermic temperatures, the patient’s blood would be substituted with an organ preservation solution to reduce blood complications associated with lower temperatures. When the patient’s core temperature approaches the freezing point of water, the organ preservation solution would be replaced by a vitrification agent to allow an ice-free descent to cryogenic temperatures for long term care. After lowering the patient’s temperature below the glass transition point (Tg), the patient is maintained at intermediate temperatures to reduce the risk of thermal stress and fracturing that would occur at lower cryogenic temperatures.

If such hospital based human cryopreservation will be available, most of the injury that is currently incurred by cryonics patients can be eliminated. No longer do cryonics patients have to suffer harmful periods of shock, cerebral ischemia, and circulatory arrest before intervention is possible. Cryonics as emergency medicine will be confined to cases that constitute unexpected life-threatening events.

As this brief, but simplified, description of hospital based (or assisted) cryonics makes clear, ischemic brain injury is something that can be eliminated from cryonics procedures if the current restriction to limit cryonics procedures to clinically dead people were lifted. Such a change will not only improve the quality of cryonics procedures, it will also make cryonics available to cardiac arrest and stroke victims who can be resuscitated with contemporary technologies but will suffer delayed brain injury (often leading to higher-brain death) if they are allowed to resume life at normothermic temperatures.

Contemporary cryonics procedures do not need to cause “irreversible” brain injury or  massive freezing damage. There is good reason to believe that in ideal cases existing cryonics procedures can be successfully reversed up to the point of cryoprotective perfusion. The major limiting factor in cryonics is not “brain death” or freezing  but cryoprotectant toxicity. But even in this area cryonics associated research  companies are setting the standard for conventional cryobiology, as demonstrated by Alcor’s implementation of the vitrification agent M22 to cryopreserve its patients.