Skip to content

Cryonics - the cryopreservation procedure

· Sandra · Science blog

Kryonik – Ablauf einer Kryokonservierung

What happens to me if I die after having signed a cryonics contract? This is one of the first questions that comes up when you are deciding whether to sign a cryonics contract.

It depends on the manner of death and the circumstances

The answer depends on the manner of death and the circumstances under which the patient dies. For the success of cryopreservation, it is beneficial to die of cancer or another disease with a "lead time", so that you can prepare for death. A sudden and unexpected death, e.g. from a heart attack, is less favorable. The worst case is to die in an accident in which the brain suffers severe damage or perhaps can no longer be found at all.

First, however, we need to look briefly at when cryopreservation begins - and what exactly the transition between life and death looks like.

Are cryopreserved people already dead?

Most people see death as a kind of switch: a person is either definitely alive or definitely dead. However, this view is misleading.

Death as a process

Rather, death is a process in which more and more cells (and thus organs) in the body slowly die off due to a lack of oxygen. Legal death is relevant insofar as the cryopreservation procedure may only be started from this point on. However, this does not mean that the person is irretrievably gone at that point or that all of their cells are dead. It merely means that a doctor officially declares that, with their knowledge and the current state of technology, nothing more can be done for the person.

Dead or not dead? - Information-theoretic death

While the patients are in storage, they are not alive (because their body no longer functions), but they are not dead either. A person is only finally dead when the structures responsible for their memories, personality and identity are irretrievably destroyed. Cryonicists call this state information-theoretic death.1 Cryopreserved people are in a kind of intermediate stage - comparable to the twilight between day and night.

How blurred the line between life and death is can be seen in cases such as that of the Swedish woman Anna Bågenholm, who in 1999 was resuscitated without lasting damage after three hours of clinical death.2

Doesn't the brain die after four to six minutes without oxygen?

Today, it is widely assumed that brain death occurs after four to six minutes without oxygen. That is not quite correct: the brain does not "die" after four to six minutes because it is immediately destroyed at that point, but because of reperfusion injury: a series of destructive processes that, paradoxically, are caused in such a case by resuscitation - that is, by the restoration of warm blood flow. Above all, it is inflammatory processes that clog the blood vessels and prevent the brain cells from being supplied with oxygen, which then actually leads to the death of the cells (but over a period of several hours, not minutes).

Experiments that delay brain death

Even today, experimental treatments can extend the period of time that can be survived during circulatory arrest without brain damage to more than ten minutes. The most important of these is artificial hypothermia - lowering the body temperature by a few degrees or using cooled blood. With every ten-degree drop in temperature, metabolic demand falls by 50%. This is one of the reasons why neurosurgery can do what it does - or why bypass operations are possible. In these procedures, patients are cooled to 34°C or 35°C to slow down metabolic processes and protect the brain during the vulnerable phase. Other measures that can delay the destruction of the brain are opening clogged vessels by raising blood pressure, thinning the blood, avoiding excessive oxygen enrichment and inhibiting cell death with medication.

In some animal studies, the brains of animals have even been brought back without neurological deficits after 16 minutes. In a few studies, researchers at the Max Planck Institute for Metabolism Research (then the Max Planck Institute for Neurological Research) even succeeded in restoring isolated monkey and cat brains to normal electrical function after a full hour of cardiac arrest.3 They later did the same with whole cats - albeit with moderate neurological deficits.4 And it gets even more incredible: nerve cells can become functional again even after eight hours of cardiac arrest (that is, capable of energy metabolism and axonal transport again).5 Recognizable brain cell structures and neural connectivity persist even much longer.6

When can cryonics no longer help?

After what period of time following clinical death can cryonics no longer help (or when does information-theoretic death occur)? We cannot answer this question definitively with our current knowledge, especially since we do not know what technologies the future will bring. For this reason, many members wish to be cryopreserved regardless of the delay or the severity of the damage. However, anyone who signs a cryonics contract can set down in it the conditions under which they no longer wish to be preserved.

The ideal case for cryonics: a foreseeable death

The ideal case is a foreseeable death, for example from cancer, so that a standby team is on site and can start the procedure immediately after the legal declaration of death. In such cases, the body and the brain are by far the best preserved. Alcor therefore recommends that terminally ill members move to the area before their legal death. For this purpose, it provides relocation assistance of up to 10,000 US dollars. The organization also advises members to inform it promptly of medical diagnoses and to notify it in good time if an operation is planned.

Noticing death in time is crucial

Cryonicists usually receive a bracelet or a necklace with instructions and a telephone number. This is so that the person who finds the deceased in a less favorable case knows that they must notify the provider. In addition, the provider usually supplies several cards with the contact details, which cryonicists can give to their relatives.

Alcor and CI have developed apps with which they can arrange a daily call at a predetermined time to make sure that a member is well and to check whether there are any changes in their health.7 If the member still does not answer after several attempts, a contact person is alerted, for example a family member or neighbor.

Devices for the early detection of death

The organizations are looking at heart rate monitors and other devices that could provide rapid notification. Tomorrow Biostasis is currently developing an app that is compatible with wearables (e.g. smartwatches) and can notify the company immediately when vital functions stop.8 Another technique already being used successfully is called ballistocardiography: motion sensors that are placed under the mattress of very old or chronically ill people and measure the mechanical vibrations of the body caused by the heartbeat or by breathing. In this way, the system can usually detect an emergency at night within less than three minutes.

The non-profit organization Cryonics Monitoring provides an overview of the monitoring systems for cryonicists developed so far and evaluates them.9

The cryonics procedure in the ideal case

The cryonics procedure: from death to cooling, vitrification and storage in insulated containers

So how exactly does the cryopreservation process work? If the ideal case applies and the team can start the procedure immediately after the declaration of death, blood circulation and breathing are first artificially restored with a mechanical cardiopulmonary resuscitation device (CPR device). This device works with pressurized oxygen and gets the circulation going much better than manual cardiopulmonary resuscitation.

Cooling as quickly as possible

What happens in all cases: the patient is covered with ice cubes and doused with cold water in order to cool the body as quickly as possible. The patient is then given cell-protecting, anticoagulant, antibiotic and anesthetic medications. Examples are sodium citrate (protects nerve cells), heparin (anticoagulant), minocycline (antibiotic) and propofol (anesthetic, also protects nerve cells). Now the cryonics team can transport the patient in the ice water bath to the facility, where they prepare the patient for further cooling.

Use of a preservation solution for long-distance transport

If the patient is far away from the cryonics facility and has to be brought there by plane, their blood is replaced by a preservation solution whose temperature is a few degrees above freezing and which keeps the cells in the body alive. This treatment is similar to those used by transplant surgeons to keep organs viable while they are transported across the country for transplantation - with the difference that here it is applied to the whole body. Relatively little known is how much this can increase survivability at cold temperatures: studies show that whole animals can survive up to three hours of storage on ice with the technology available today.10 They can survive even longer periods if the preservation solution is continuously circulated.11

In some such cases, Alcor also uses a procedure called FCP (Field Cryoprotection). In this procedure, at least the head is already vitrified at the place of death (see next paragraph) and the patient is brought to the facility at -79°C on dry ice instead of in ice water.

Vitrification - artificial circulation for introducing the cryoprotectant

At the cryonics facility, an artificial circulation is first established. For this purpose, either the vessels of the neck are opened (in order to preserve the brain in particular as well as possible), or the chest is opened and tubes are inserted into the large vessels leaving the heart. Then a cell-protecting solution flows into the body via an artery and flushes the blood out via a vein. The cryoprotectant (a liquid that prevents ice crystals from forming during cooling, which would tear the tissue) is added to the solution in increasing concentration until it makes up about 70% of the mixture. This ensures that the cryoprotectant also reaches almost all cells and reliably vitrifies the body.

Is ice-free cryopreservation of the brain possible?

Some scientists have claimed that ice-free cryopreservation of the brain is not possible because the cryoprotectant does not reach all parts of the brain.12 However, vitrification uses exactly the same vessels that constantly supply the brain with oxygen and nutrients. Ice-free preservation of the brain has been demonstrated both in the laboratory13 and in a few selected cases of cryopreserved members14. It is true that the blood-brain barrier delays the uptake of the cryoprotectant. The consequence of this, however, is that water is drawn out of the brain by the osmotic imbalance that arises while the cryoprotectant is being introduced. This makes the brain even more resistant to the formation of ice crystals. However, the dehydration of the brain appears to lead to ultrastructural changes (changes in the fine structure of the brain that can only be made visible with electron microscopy), which is indeed a still unsolved problem of cryonics. In "good" cryonics cases, dehydration of up to 50% of the total brain volume can be observed. At the moment, we do not yet know to what degree the lack of fluid will still allow the function of the brain to be restored in the future - if this will be possible at all.

Gradual cooling of the patient

Replacing the blood with the cryoprotectant takes several hours and takes place at a body temperature of about 0°C. The patients are then placed in a cooling box and cooled under computer control: liquid nitrogen is injected and evaporates, and a fan circulates the nitrogen gas at nearly -125°C. The aim is to cool all parts of the patient below -124°C (the temperature at which the cryoprotectant solidifies and changes into a glass-like state) as quickly as possible in order to avoid any ice formation. This takes about three hours, at the end of which the patient is "vitrified" (has reached a stable ice-free state). The patient is then cooled further to -196°C over a period of several days using the same technique.

Cooling causes harmful fractures in the tissue

In principle, -125°C would actually be enough: as soon as the cryoprotectant is solid, all metabolic activity has come to a halt. However, -196°C is the temperature of liquid nitrogen, which is a safe, non-toxic, cheap and readily available coolant. Unfortunately, during further cooling, thermal stresses cause large-scale fractures in the tissue (for example due to uneven cooling rates, different expansion coefficients of bone and muscle, and so on), which is a problem that has not yet been solved. It is important to note that these fractures are not open wounds. A good comparison is an intact but cracked glass windshield. The fractures may sound like a serious problem. However, future medicine will probably be able to repair them well, because they cause no significant loss of information: the damage occurs on a larger scale and does not destroy any important structures (as would be the case with ice crystal formation). Alcor is currently testing a new storage system that works with warmer temperatures in order to avoid the fractures in the future.15 (One of our upcoming posts will take a closer look at a new approach that tackles this problem from a completely different angle: helium persufflation.)

Storing the patient in an insulated container

The patient is stored in a large insulated container filled with liquid nitrogen (for example, a Dewar flask), which is checked every day. All that is needed is to top up some nitrogen about once a week. The patient is stored head down so that, in the event of an accident with a major nitrogen leak, the head is protected for as long as possible.

A cryopreserved member shares a container with three others. In the case of neuro preservation, in which only the brain is put into cold sleep, there are usually around 45 brains stored together. The brains remain in the head during preservation, as this involves fewer risks.

For cooling, no electricity at all is needed - it is provided exclusively by the liquid nitrogen. This also refutes the misconceptions that a power outage would ruin everything or that storage causes a lot of CO2 emissions.

Will I lose my memories during cryopreservation?

We can be fairly sure that this is not the case. Very short-term memories (from the last 30 seconds up to a few minutes at most) are stored only in electrochemical activity, but everything beyond that takes the form of physical changes in the brain: changes in the synapses, in the levels of certain neurotransmitters, in the protein content and so on.16

Are these changes preserved during the cryopreservation process? To test this, researchers carried out a study in 2015 on the well-known model organism C. elegans (a roundworm). They used a method of sensory imprinting to test long-term olfactory memory in the worms. After being cryopreserved and revived, the worms were able to recall the induced olfactory memory. So the structures required for this had not been destroyed by freezing.17

In 2020, scientists in another study examined the effects of cryopreservation on the brain of a woman who had donated her body. The results again showed that there was no adverse effect on the thickness of the hippocampus or of the cerebral cortex - both regions that play a central role in storing memories.18

Brain fog: when memories are blurry

What could occur, however, is a temporary condition called "brain fog". This would mean that your own memories are initially somewhat blurry while the brain slowly resumes all its functions after revival. Short-term memory loss and brain fog are common side effects in heart attack patients. The reason is a temporary lack of oxygen in a certain area of the hippocampus, which leads to the death of the neurons there.19 Fortunately, scientists are already working on a way to restore the neurons in this area, so that we may no longer have this problem at all in the future.20

Cryonics: revival

Now we come to the most challenging part: revival. No one can currently say with certainty whether it will be possible to bring people out of the liquid nitrogen back to life. Several steps are necessary for this: the cause of death must be cured, the patient must be rejuvenated, the rewarming and restarting of brain and other bodily functions must succeed, and any damage that has occurred must be repaired. In addition, we must manage to reintegrate the patient into society. Klaus Sames speaks somewhat jokingly of perhaps first bringing some people who have been brought back to life into a cyberspace that simulates the 21st century, so as not to trigger a culture shock. This article by Tomorrow Biostasis provides a good overview of the prerequisites for successful reanimation.

The only certainty is that this requires technologies that we do not yet have available in the required form today. They are, however, quite foreseeable: artificial intelligence, tissue engineering, bioprinting and, above all, nanomedicine are making impressive progress. Robert Freitas, a pioneer of nanotechnology, published his 700-page book "Cryostasis Revival: The Recovery of Cryonics Patients through Nanomedicine" last year, in which he outlines a possible path to the reanimation and healing of cryopreserved people with the help of nanorobots.21 A summary of his book can be found here.

Challenges in reviving cryopreserved people

When rewarming, there are three problems in particular to solve: on the one hand, the toxicity of the cryoprotectant, and on the other hand, the formation of ice crystals. Furthermore, the tissue must be warmed evenly. If the body is simply warmed, the cryoprotectant liquefies and, because of its toxicity above the glass transition temperature, damages the cells. To prevent this, the cryoprotectant must be replaced by blood before rewarming. But then a strange phenomenon called recrystallization occurs: during the warming process, ice crystals can form anew and damage the tissue. The only option is therefore to thaw the body so quickly that no ice can form. We currently still lack the technology needed for this.

Nanowarming - magnetic nanoparticles for even warming

Researchers now repeatedly succeed in cryopreserving individual organs such as kidneys and rewarming them quickly and uniformly enough to keep them functional. One method used for this is nanowarming: magnetic nanoparticles that are introduced together with the cryoprotectant. We can excite these nanoparticles with radiofrequency fields, which leads to rapid and uniform warming.

The article "Vitrification and Nanowarming of Kidneys" describes a successful nanowarming experiment on a rat kidney.22 During the experiment, the researchers perfused rat kidneys with a cryoprotective solution and silica-coated iron oxide nanoparticles (sIONPs). They then excited the nanoparticles by applying a radiofrequency field. The vitrified kidneys were successfully rewarmed: modeling shows that both ice crystal formation and fractures were absent during these processes. However, the researchers found damage caused by the toxicity of the cryoprotectants used. Which means that we need to develop better cryoprotectants.23

So there is definitely still a lot of research work ahead of us before we can successfully rewarm a brain or an entire body with nanowarming.

Ultrasound for warming tissue

Another approach, pursued for example by Ramon Risco, is the warming of tissue by means of ultrasound.24 This approach is to be tested first on C. elegans and then on rodents, but can probably be scaled up as far as needed. You will soon learn more about this in our post on current research relevant to cryonics!

So there are still a great many problems to solve for a successful revival. However: time plays practically no role, since there is no expiration date for cryopreservation. Storage continues indefinitely (at no additional cost), and science keeps advancing.

Sources:

  1. https://en.longevitywiki.org/wiki/Information_theoretic_death
  2. https://de.wikipedia.org/wiki/Anna_B%C3%A5genholm
  3. Hossmann KA, Sato K. Recovery of neuronal function after prolonged cerebral ischemia. Science 1970 Apr 17; 168(3929): 375-6. doi: 10.1126/science.168.3929.375.
  4. Hossmann KA, Schmidt-Kastner R, Grosse Ophoff B. Recovery of integrative central nervous function after one hour global cerebro-circulatory arrest in normothermic cat. J Neurol Sci 1987 Feb; 77(2-3): 305-20. doi: 10.1016/0022-510x(87)90130-4.
  5. Dai J, Swaab DF, Buijs RM. Recovery of axonal transport in "dead neurons". Lancet 1998 Feb 14; 351(9101): 499-500. doi: 10.1016/S0140-6736(05)78689-X.
  6. de Wolf A, Phaedra C, Perry RM, Maire M. Ultrastructural Characterization of Prolonged Normothermic and Cold Cerebral Ischemia in the Adult Rat. Rejuvenation Res 2020 Jun; 23(3): 193-206. doi: 10.1089/rej.2019.2225.
  7. https://www.cryonicsmonitoring.org/review-post/review-alcor-check-in-app | https://www.cryonicsmonitoring.org/review-post/review-ci-check-in-app
  8. https://www.cryonicsmonitoring.org/review-post/tomorrow-bio-monitoring-app
  9. https://www.cryonicsmonitoring.org/
  10. Haneda K, Thomas R, Sands MP, Breazeale DG, Dillard DH. Whole body protection during three hours of total circulatory arrest: an experimental study. Cryobiology 1986 Dec; 23(6): 483-94. doi: 10.1016/0011-2240(86)90057-x.
  11. Taylor MJ, Bailes JE, Elrifai AM, Shih TS, Teeple E, Leavitt ML, Baust JC, Maroon JC. Asanguineous whole body perfusion with a new intracellular acellular solution and ultraprofound hypothermia provides cellular protection during 3.5 hours of cardiac arrest in a canine model. ASAIO J 1994 Jul-Sep; 40(3): M351-8. doi: 10.1097/00002480-199407000-00022.
  12. https://www.bbc.com/news/business-43259902
  13. Lemler J, Harris SB, Platt C, Huffman TM. The arrest of biological time as a bridge to engineered negligible senescence. Ann N Y Acad Sci 2004 Jun; 1019: 559-63. doi: 10.1196/annals.1297.104.
  14. https://www.cryonicsarchive.org/library/complete-list-of-alcor-cryopreservations/ct-scan-a-1002/
  15. https://www.cryonicsarchive.org/library/faq-technical-questions/#fracturing
  16. https://www.deutsche-apotheker-zeitung.de/news/artikel/2011/02/08/wie-das-gehirn-erinnerungen-speichert
  17. Vita-More N, Barranco D. Persistence of Long-Term Memory in Vitrified and Revived Caenorhabditis elegans. Rejuvenation Res 2015 Oct; 18(5): 458-63. doi: 10.1089/rej.2014.1636.
  18. Canatelli-Mallat M, Lascaray F, Entraigues-Abramson M, Portiansky EL, Blamaceda N, Morel GR, Goya RG. Cryopreservation of a Human Brain and Its Experimental Correlate in Rats. Rejuvenation Res 2020 Dec; 23(6): 516-525. doi: 10.1089/rej.2019.2245.
  19. https://www.tomorrow.bio/post/can-cryopreservation-store-memories
  20. https://www.fiercebiotech.com/research/restoring-neurons-to-preserve-memory-after-heart-attack-or-stroke
  21. https://www.amazon.de/Cryostasis-Revival-Recovery-Cryonics-Nanomedicine/dp/099681535X
  22. https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202101691
  23. https://www.tomorrow.bio/post/recent-scientific-articles-cryopreservation
  24. https://www.youtube.com/watch?v=GZkLBauiLL8

Further reading:

Authors: Moritz Pohl, proofread by Sandra Borst