 | This article mayrequirecleanup to meet Wikipedia'squality standards. The specific problem is:the article has problems with clarity, grammar, spacing, punctuation and tone. Please helpimprove this article if you can.(June 2017) (Learn how and when to remove this message) |
Suspended animation is the slowing or stopping of biological function so that physiological capabilities are preserved. States of suspended animation are common in micro-organisms and some plant tissue, such as seeds. Many animals, including large ones, may undergohibernation, and most plants have periods ofdormancy. This article focuses primarily on the potential of large animals, especially humans, to undergo suspended animation.
In animals, suspended animation 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 ofhibernation. When applied with therapeutic intent, as indeep hypothermic circulatory arrest (DHCA), usually technologically mediated revival is required.[1][2]
Suspended animation is understood as the pausing oflife processes by external or internal means without terminatinglife 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 contextshibernation,dormancy oranabiosis (the latter in some aquatic invertebrates and plants in scarcity conditions).
In July 2020,marine biologists reported thataerobicmicroorganisms (mainly), in "quasi-suspended animation", were found inorganically-poor sediments, up to 101.5 million years old, 68.9 metres (226 feet) below thesea floor in theSouth Pacific Gyre (SPG) ("the deadest spot in the ocean"), and could be thelongest-living life forms ever found.[5][6]
This condition of apparentdeath or interruption of vital signs in humans 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 ormolecular death principally caused by oxygen deprivation or excess temperature (especially high temperature).[7]
Cases have been reported of individuals having returned from this apparent interruption of life lasting over one half hour, two hours, eight hours, or more (while adhering to these specific conditions for oxygen and temperature) have been analysed in depth, but these cases are considered rare and unusual phenomena. 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 after apparent suspended animation in such instances as 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 they 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 isAnna Bågenholm, a Swedish radiologist who allegedly survived 80 minutes under ice in a frozen lake in a state ofcardiac arrest with no brain damage in 1999.[9][10]
Other cases ofhypothermia where people survived without damage are:
It has been suggested that bone lesions provide evidence of hibernation among the early human population whose remains have been retrieved at theArchaeological site of Atapuerca. In a paper published in the journalL'Anthropologie, researchersJuan-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 someopen-heart surgeries as an alternative toheart-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 "inducedhibernation" 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 oftorpor, 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]
Lowering the temperature of a substance reduces its chemical activity by theArrhenius equation. This includes life processes such as metabolism.Cryonics could eventually provide long-term suspended animation.[19]
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 fortherapeutic hypothermia.[20]
In June 2005, scientists at theUniversity of Pittsburgh's Safar Center for Resuscitation Research announced they had managed to placedogs in suspended animation and bring them back to life, most of them withoutbrain damage, by draining theblood out of the dogs' bodies and injecting a low temperature solution into theircirculatory systems, which in turn keeps the bodies alive in stasis. After three hours of beingclinically dead, the dogs' blood was returned to their circulatory systems, and the animals were revived by delivering anelectric 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 theMassachusetts General Hospital inBoston announced they had placedpigs in suspended animation with a similar technique. The pigs wereanaesthetized 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]
The laboratory ofMark Roth at theFred Hutchinson Cancer Research Center and institutes such asSuspended Animation, Inc are trying to implement suspended animation as a medical procedure which involves the therapeutic induction to a complete and temporary systemicischemia, 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]
{{cite journal}}:Cite journal requires|journal= (help){{cite journal}}:Cite journal requires|journal= (help){{cite journal}}:Cite journal requires|journal= (help)| International | |
|---|---|
| Other | |
