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Cardiopulmonary resuscitation (CPR) being performed on a trauma patient in a hospital of Maracay, Venezuela. Like CPR, suspended animation could delay the onset of cell death (necrosis) in seriously injured or ill patients, providing them with more time to receive definitive medical treatment.

Suspended animation is the temporary (short- or long-term) slowing or stopping of biological function so that physiological capabilities are preserved. It may be either hypometabolic or ametabolic in nature. It may be induced by either endogenous, natural or artificial biological, chemical or physical means. In its natural form, it may be spontaneously reversible as in the case of species demonstrating hypometabolic states of hibernation. When applied with therapeutic intent, as in deep hypothermic circulatory arrest (DHCA), usually technologically mediated revival is required.[1][2]

Basic principles

Suspended animation is understood as the pausing of life processes by exogenous or endogenous means without terminating life itself.[3] Breathing, heartbeat and other involuntary functions may still occur, but they can only be detected by artificial means.[4] For this reason, this procedure has been associated with a lethargic state in nature when animals or plants appear, over a period, to be dead but then can wake up or prevail without suffering any harm. This has been termed in different contexts hibernation, dormancy or anabiosis (the latter in some aquatic invertebrates and plants in scarcity conditions).

The revived microorganisms

In July 2020, marine biologists reported that aerobic microorganisms (mainly), in "quasi-suspended animation", were found in organically-poor sediments, up to 101.5 million years old, 68.9 metres (226 feet) below the seafloor in the South Pacific Gyre (SPG) ("the deadest spot in the ocean"), and could be the longest-living life forms ever found.[5][6]

This condition of apparent death or interruption of vital signs may be similar to a medical interpretation of suspended animation. It is only possible to recover signs of life if the brain and other vital organs suffer no cell deterioration, necrosis or molecular death principally caused by oxygen deprivation or excess temperature (especially high temperature).[7]

Some examples of people that have returned from this apparent interruption of life lasting over half an hour, two hours, eight hours or more while adhering to these specific conditions for oxygen and temperature have been reported and analysed in depth, but these cases are not considered scientifically valid. The brain begins to die after five minutes without oxygen; nervous tissues die intermediately when a "somatic death" occurs while muscles die over one to two hours following this last condition.[8]

It has been possible to obtain a successful resuscitation and recover life in some instances, including after anaesthesia, heat stroke, electrocution, narcotic poisoning, heart attack or cardiac arrest, shock, newborn infants, cerebral concussion, or cholera.

Supposedly, in suspended animation, a person technically would not die, as long as he or she were able to preserve the minimum conditions in an environment extremely close to death and return to a normal living state. An example of such a case is Anna Bågenholm, a Swedish radiologist who allegedly survived 80 minutes under ice in a frozen lake in a state of cardiac arrest with no brain damage in 1999.[9] [10]

Other cases of hypothermia where people survived without damage are:

Human hibernation

Main article: Therapeutic hypothermia

The American toad (Anaxyrus americanus) is an amphibian that can hibernate in winter.

It has been suggested that bone lesions provide evidence of hibernation among the early human population whose remains have been retrieved at the Archaeological site of Atapuerca. In a paper published in the journal L’Anthropologie, researchers Juan-Luis Arsuaga and Antonis Bartsiokas point out that “primitive mammals and primates” like bush babies and lorises hibernate, which suggests that “the genetic basis and physiology for such a hypometabolism could be preserved in many mammalian species, including humans”.[15]

Since the 1970s, induced hypothermia has been performed for some open-heart surgeries as an alternative to heart-lung machines. Hypothermia, however, provides only a limited amount of time in which to operate and there is a risk of tissue and brain damage for prolonged periods.

There are many research projects currently investigating how to achieve "induced hibernation" in humans.[16][17] This ability to hibernate humans would be useful for a number of reasons, such as saving the lives of seriously ill or injured people by temporarily putting them in a state of hibernation until treatment can be given.

The primary focus of research for human hibernation is to reach a state of torpor, defined as a gradual physiological inhibition to reduce oxygen demand and obtain energy conservation by hypometabolic behaviors altering biochemical processes. In previous studies, it was demonstrated that physiological and biochemical events could inhibit endogenous thermoregulation before the onset of hypothermia in a challenging process known as "estivation". This is indispensable to survive harsh environmental conditions, as seen in some amphibians and reptiles.[18]

Scientific possibilities


Lowering the temperature of a substance reduces its chemical activity by the Arrhenius equation. This includes life processes such as metabolism. Cryonics could eventually provide long-term suspended animation.[19]

Emergency Preservation and Resuscitation

Emergency Preservation and Resuscitation (EPR) is a way to slow the bodily processes that would lead to death in cases of severe injury.[20] This involves lowering the body's temperature below 34 °C (93 °F), which is the current standard for therapeutic hypothermia.[20]

Hypothermic experiments on animals

In June 2005, scientists at the University of Pittsburgh's Safar Center for Resuscitation Research announced they had managed to place dogs in suspended animation and bring them back to life, most of them without brain damage, by draining the blood out of the dogs' bodies and injecting a low temperature solution into their circulatory systems, which in turn keeps the bodies alive in stasis. After three hours of being clinically dead, the dogs' blood was returned to their circulatory systems, and the animals were revived by delivering an electric shock to their hearts. The heart started pumping the blood around the body, and the dogs were brought back to life.[21]

On 20 January 2006, doctors from the Massachusetts General Hospital in Boston announced they had placed pigs in suspended animation with a similar technique. The pigs were anaesthetized and major blood loss was induced, along with simulated - via scalpel - severe injuries (e.g. a punctured aorta as might happen in a car accident or shooting). After the pigs lost about half their blood the remaining blood was replaced with a chilled saline solution. As the body temperature reached 10 °C (50 °F) the damaged blood vessels were repaired and the blood was returned.[22] The method was tested 200 times with a 90% success rate.[23]

Chemically induced

The laboratory of Mark Roth at the Fred Hutchinson Cancer Research Center and institutes such as Suspended Animation, Inc are trying to implement suspended animation as a medical procedure which involves the therapeutic induction to a complete and temporary systemic ischemia, directed to obtain a state of tolerance for the protection-preservation of the entire organism, this during a circulatory collapse "only by a limited period of one hour". The purpose is to avoid a serious injury, risk of brain damage or death, until the patient reaches specialized attention.[24]

See also


  1. ^ "Suspended Animation".
  2. ^ Asfar, P; Calzia, E; Radermacher, P (2014). "Is pharmacological, H2S-induced 'suspended animation' feasible in the ICU?". Crit Care. 18 (2): 215. doi:10.1186/cc13782. PMC 4060059. PMID 25028804.
  3. ^ Asfar, P. (2014). "Is pharmacological, H2S-induced 'suspended animation' feasible in the ICU?". Critical Care. 182 (2): 215. doi:10.1186/cc13782. PMC 4060059. PMID 25028804.
  4. ^ "How do frogs survive winter? Why don't they freeze to death?". Scientific American. 11 July 2014. Retrieved 3 June 2017.
  5. ^ Wu, Katherine J. (28 July 2020). "These Microbes May Have Survived 100 Million Years Beneath the Seafloor - Rescued from their cold, cramped and nutrient-poor homes, the bacteria awoke in the lab and grew". The New York Times. Retrieved 31 July 2020.
  6. ^ Morono, Yuki; et al. (28 July 2020). "Aerobic microbial life persists in oxic marine sediment as old as 101.5 million years". Nature Communications. 11 (3626): 3626. Bibcode:2020NatCo..11.3626M. doi:10.1038/s41467-020-17330-1. PMC 7387439. PMID 32724059.
  7. ^ "Molecular death is". Forensic ((cite journal)): Cite journal requires |journal= (help)
  8. ^ "Definition of suspended animation is". Forensic Archived from the original on 29 June 2018. Retrieved 6 June 2017. ((cite journal)): Cite journal requires |journal= (help)
  9. ^ "'Miracle' student survived his body being frozen solid". 20 January 2016. Archived from the original on 25 May 2022. Retrieved 5 June 2017.
  10. ^ Gilbert M, Busund R, Skagseth A, Nilsen P, Solbo J (2000). "Resuscitation from accidental hypothermia of 13.7°C with circulatory arrest". The Lancet. 355 (9201): 375–376. doi:10.1016/S0140-6736(00)01021-7. PMID 10665559. S2CID 54348869.
  11. ^ Suspended Animation? How A Boy Survived 15 Minutes Trapped Under Ice In Frozen Lake at Medical Daily
  12. ^ Japanese man in mystery survival at BBC News
  13. ^ Eleva boy’s story part of national tour to honor Mayo Clinics 150 years Archived 11 May 2015 at the Wayback Machine Mayo Clinic
  14. ^ Warick, Jason (23 February 2002). "'Miracle child' bears few scars one year after brush with death". Edmonton Journal. p. A3.
  15. ^ Sullivan, R (2020). "Early humans may have hibernated". Archived from the original on 25 May 2022. Retrieved 25 November 2021. This article refers to Bartsiokas, A. & Arsuaga, J. (2020). Hibernation in hominins from Atapuerca, Spain half a million years ago. L'Anthropologie, Volume 124, Issue 5
  16. ^ New Hibernation Technique might work on humans | LiveScience at
  17. ^ Race to be first to 'hibernate' human beings - Times Online at
  18. ^ "Is Human Hibernation Possible?" (PDF). ((cite journal)): Cite journal requires |journal= (help)
  19. ^ Tandy C (2014). The Prospect of Immortality − Fifty Years Later. Ria University Press, USA, ISBN 978-1-934297-21-6
  20. ^ a b Delbert, Caroline (20 November 2019). "Doctors Place Humans in True Suspended Animation for First Time". Popular Mechanics. Retrieved 29 September 2020.
  21. ^ Mihm, Stephen (11 December 2005). "Zombie Dogs". The New York Times.
  22. ^ Alam HB, Rhee P, Honma K, Chen H, Ayuste EC, Lin T, Toruno K, Mehrani T, Engel C, Chen Z (2006). "Does the rate of rewarming from profound hypothermic arrest influence the outcome in a swine model of lethal hemorrhage?". J Trauma. 60 (1): 134–146. doi:10.1097/ PMID 16456447.
  23. ^ "Doctors claim suspended animation success". The Sydney Morning Herald. 20 January 2006. Retrieved 10 October 2006.
  24. ^ Bellamy, R; Safar, P; Tisherman, S. A; Basford, R; Bruttig, S. P; Capone, A; Dubick, M. A; Ernster, L; Hattler Jr, B. G; Hochachka, P; Klain, M; Kochanek, P. M; Kofke, W. A; Lancaster, J. R; McGowan Jr, F. X; Oeltgen, P. R; Severinghaus, J. W; Taylor, M. J; Zar, H (1996). "Suspended animation for delayed resuscitation. Crit Care Med. 1996 Feb;24(2 Suppl):S24-47". Critical Care Medicine. 24 (2 Suppl): S24–47. doi:10.1097/00003246-199602000-00046. PMID 8608704.