Suspended animation

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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. Intrahospital CPR.jpg
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 or require technologically mediated revival when applied with therapeutic intent in the medical setting as in the case of deep hypothermic circulatory arrest ('DHCA') [1] [2]


Basic principles

Hazel-mouse, (Muscardinus avellanarius) preparing for hibernation, gaining nearly double its body weight. Bonn, Zoological Research Institute and Museum. Bonner zoologische Monographien (1975) (20367841916).jpg
Hazel-mouse, (Muscardinus avellanarius) preparing for hibernation, gaining nearly double its body weight. Bonn, Zoological Research Institute and Museum.

Suspended animation has been understood as the slowing or stopping 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 (this last in some aquatic invertebrates and plants in scarcity conditions).

Hibernation process in which an organism enters and maintains a period of dormancy in which to pass the winter, characterized by narcosis and by sharp reduction in body temperature and metabolic activity and by a depression of vital signs

Hibernation is a state of inactivity and metabolic depression in endotherms. Hibernation refers to a season of heterothermy characterized by low body temperature, slow breathing and heart rate, and low metabolic rate. It is most commonly observed during the winter months. Although traditionally reserved for "deep" hibernators such as rodents, the term has been redefined to include animals such as bears and is now applied based on active metabolic suppression rather than any absolute decline in body temperature. Many experts believe that the processes of daily torpor and hibernation form a continuum and utilize similar mechanisms. The equivalent during the summer months is aestivation.

Dormancy state of minimized physical activity of an organism

Dormancy is a period in an organism's life cycle when growth, development, and physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be closely associated with environmental conditions. Organisms can synchronize entry to a dormant phase with their environment through predictive or consequential means. Predictive dormancy occurs when an organism enters a dormant phase before the onset of adverse conditions. For example, photoperiod and decreasing temperature are used by many plants to predict the onset of winter. Consequential dormancy occurs when organisms enter a dormant phase after adverse conditions have arisen. This is commonly found in areas with an unpredictable climate. While very sudden changes in conditions may lead to a high mortality rate among animals relying on consequential dormancy, its use can be advantageous, as organisms remain active longer and are therefore able to make greater use of available resources.

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). [5]

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. [6]

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, cholera, and voluntarily as in yogis.

Yogi practitioner of Yoga

A yogi is a practitioner of yoga, including a sannyasin or practitioner of meditation in Indian religions. The feminine form, sometimes used in English, is yogini.

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 40 minutes under ice in a frozen lake in a state of cardiac arrest and survived with no brain damage in 1999. [7]

Anna Elisabeth Johansson Bågenholm is a Swedish radiologist from Vänersborg, who survived after a skiing accident in 1999 left her trapped under a layer of ice for 80 minutes in freezing water. During this time she became a victim of extreme hypothermia and her body temperature decreased to 13.7 °C (56.7 °F), one of the lowest survived body temperatures ever recorded in a human with accidental hypothermia. Bågenholm was able to find an air pocket under the ice, but suffered circulatory arrest after 40 minutes in the water.

Cardiac arrest sudden stop in effective blood flow due to the failure of the heart to contract effectively

Cardiac arrest is a sudden loss of blood flow resulting from the failure of the heart to effectively pump. Signs include loss of consciousness and abnormal or absent breathing. Some individuals may experience chest pain, shortness of breath, or nausea before cardiac arrest. If not treated within minutes, it typically leads to death.

Other cases of hypothermia where people survived without damage are:

Human hibernation

American toad (Bufo americanus) is an amphibian that can hibernate in winter. American toad - Bufo americanus - 3.JPG
American toad (Bufo americanus) is an amphibian that can hibernate in winter.

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. [12] [13] 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. [14]

Scientific possibilities


Lowering the temperature of a substance reduces chemical activity by the Arrhenius equation. This includes life processes such as metabolism.

Hypothermic range

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. [15]

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. [16] The method was tested 200 times with a 90% success rate. [17]

From May 2014, a team of surgeons from UPMC Presbyterian Hospital in Pittsburgh plan to try the above method in gunshot victims (or those suffering from similar traumatic injuries). The trials will be done on ten such severely wounded patients and compared with ten others in similar situation but who had no access to the above method. They currently refer to the procedure as Emergency Preservation and Resuscitation for Cardiac Arrest from trauma. [18]

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 to avoid a serious injury, risk of brain damage or death, until the patient reaches specialized attention. [19]

Genetically induced

Ongoing research is being conducted into Tardigrades to isolate the genes responsible for their metabolic transformation into a glass-like state, thus fully preserving them for decades in dry conditions. [20]

See also

Related Research Articles

Clinical death is the medical term for cessation of blood circulation and breathing, the two necessary criteria to sustain human and many other organisms' lives. It occurs when the heart stops beating in a regular rhythm, a condition called cardiac arrest. The term is also sometimes used in resuscitation research.

Hypothermia A human body core temperature below 35.0°C

Hypothermia is reduced body temperature that happens when a body dissipates more heat than it absorbs. In humans, it is defined as a body core temperature below 35.0 °C (95.0 °F). Symptoms depend on the temperature. In mild hypothermia there is shivering and mental confusion. In moderate hypothermia shivering stops and confusion increases. In severe hypothermia, there may be paradoxical undressing, in which a person removes their clothing, as well as an increased risk of the heart stopping.

Drowning Respiratory impairment resulting from being in or under a liquid

Drowning is defined as respiratory impairment as a result of being in or under a liquid. Drowning typically occurs silently, with only a few people able to wave their hands or call for help. Symptoms following rescue may include breathing problems, vomiting, confusion, or unconsciousness. Occasionally symptoms may not appear until up to six hours afterwards. Drowning may be complicated by low body temperature, aspiration of vomit, or acute respiratory distress syndrome.

Asystole absence of ventricular contractions lasting longer than the minimum possible to sustain life

Asystole is the absence of ventricular contractions. Asystole is the most serious form of cardiac arrest and is usually irreversible. A cardiac flatline is the state of total cessation of electrical activity from the heart, which means no tissue contraction from the heart muscle and therefore no blood flow to the rest of the body.

Cardiopulmonary bypass technique that temporarily takes over the function of the heart and lungs during surgery

Cardiopulmonary bypass (CPB) is a technique in which a machine temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and the oxygen content of the patient's body. The CPB pump itself is often referred to as a heart–lung machine or "the pump". Cardiopulmonary bypass pumps are operated by perfusionists. CPB is a form of extracorporeal circulation. Extracorporeal membrane oxygenation is generally used for longer-term treatment.

Hypovolemic shock is a medical emergency and an advanced form of hypovolemia due to insufficient amounts of blood and/or fluid inside the human body to let the heart pump enough blood to the body. More specifically, hypovolemic shock occurs when there is decreased intravascular volume to the point of cardiovascular compromise. The hypovolemic shock could be due to severe dehydration through a variety of mechanisms or from blood loss.

Cerebral hypoxia Oxygen shortage of the brain

Cerebral hypoxia is a form of hypoxia, specifically involving the brain; when the brain is completely deprived of oxygen, it is called cerebral anoxia. There are four categories of cerebral hypoxia; they are, in order of severity: diffuse cerebral hypoxia (DCH), focal cerebral ischemia, cerebral infarction, and global cerebral ischemia. Prolonged hypoxia induces neuronal cell death via apoptosis, resulting in a hypoxic brain injury.

Brain ischemia Human disease

Brain ischemia is a condition in which there is insufficient blood flow to the brain to meet metabolic demand. This leads to poor oxygen supply or cerebral hypoxia and thus to the death of brain tissue or cerebral infarction / ischemic stroke. It is a sub-type of stroke along with subarachnoid hemorrhage and intracerebral hemorrhage.

Deep hypothermic circulatory arrest (DHCA) is a surgical technique that involves cooling the body to temperatures between 20°C (68°F) to 25 °C (77 °F), and stopping blood circulation and brain function for up to one hour. It is used when blood circulation to the brain must be stopped because of delicate surgery within the brain, or because of surgery on large blood vessels that lead to or from the brain. DHCA is used to provide a better visual field during surgery due to the cessation of blood flow. DHCA is a form of carefully managed clinical death in which heartbeat and all brain activity cease.

Erika Nordby, also known as Baby Erika, Miracle Baby and Canada's Miracle Child, is a Canadian girl originally from Edmonton, Alberta. She is primarily known for having been revived after spending two hours without a heartbeat due to hypothermia.

Targeted temperature management (TTM) previously known as therapeutic hypothermia or protective hypothermia is an active treatment that tries to achieve and maintain a specific body temperature in a person for a specific duration of time in an effort to improve health outcomes during recovery after a period of stopped blood flow to the brain. This is done in an attempt to reduce the risk of tissue injury following lack of blood flow. Periods of poor blood flow may be due to cardiac arrest or the blockage of an artery by a clot as in the case of a stroke.

The Arctic Sun Temperature Management System is a non-invasive targeted temperature management system, a medical device used to modulate patient temperature with precision by circulating chilled water in pads directly adhered to the patient's skin. Using varying water temperatures and a sophisticated computer algorithm, a patient's body temperature can be controlled to the nearest 0.2 °C. It is produced by Medivance, Inc. of Louisville, Colorado.

The H's and T's is a mnemonic used to aid in remembering the possible reversible causes of cardiac arrest. A variety of disease processes can lead to a cardiac arrest; however, they usually boil down to one or more of the "H's and T's".

A hypothermia cap is a therapeutic device used to cool the human scalp. Its most prominent medical applications are in preventing or reducing alopecia in chemotherapy, and for preventing cerebral palsy in babies born with neonatal encephalopathy caused by hypoxic-ischemic encephalopathy (HIE). It can also be used to provide neuroprotection after cardiac arrest, to inhibit stroke paralysis, and as cryotherapy for migraine headaches.

Hydrogen sulfide is produced in small amounts by some cells of the mammalian body and has a number of biological signaling functions.

Extracorporeal cardiopulmonary resuscitation is a method of cardiopulmonary resuscitation (CPR) that passes the patient's blood through a machine in a process to oxygenate the blood supply. A portable extracorporeal membrane oxygenation (ECMO) device is used as an adjunct to standard CPR. A patient who is deemed to be in cardiac arrest refractory to CPR has percutaneous catheters inserted into the femoral vein and artery. Theoretically, the application of ECPR allows for the return of cerebral perfusion in a more sustainable manner than with external compressions alone. By attaching an ECMO device to a person who has acutely undergone cardiovascular collapse, practitioners can maintain end-organ perfusion whilst assessing the potential reversal of causal pathology, with the goal of improving longterm survival and neurological outcomes.

Emergency Preservation and Resuscitation (EPR) is an experimental medical procedure where an emergency department patient is cooled into suspended animation for an hour to prevent incipient death from ischemia, such as the blood loss following a shooting or stabbing. EPR uses hypothermia, drugs, and fluids to "buy time" for resuscitative surgery. If successful, EPR may someday be deployed in the field so that paramedics can suspend and preserve patients for transport.

Lance B. Becker is an American physician and academic, specializing in emergency medicine and treatment for cardiac arrest, currently at Northwell Health. He is the chairman of the department of emergency medicine at North Shore University Hospital, as well as chair and professor of emergency medicine at Hofstra Northwell School of Medicine.


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