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categories: ["space", "bodies"]categories: ["space", "bodies"]tags: ["torpor", "hypothermia", "metabolism", "spaceflight", "neuroscience", "suspended animation"]tags: ["torpor", "hypothermia", "metabolism", "spaceflight", "neuroscience", "suspended animation"]summary: "The proposal to induce a hibernation-like state of suppressed metabolism in people, and the distance between rodent torpor circuits and any clinical human application."summary: "The proposal to induce a hibernation-like state of suppressed metabolism in people, and the distance between rodent torpor circuits and any clinical human application."updated: "2026-07-27"updated: "2026-08-23"humanEvidence: "No human has been placed in torpor; every induced-torpor result is from mice and rats, and all human cooling to date is hypothermia imposed from outside against a defended set point."humanEvidence: "No human has been placed in torpor; every induced-torpor result is from mice and rats, and all human cooling to date is hypothermia imposed from outside against a defended set point."issues: ["The emergency preservation and resuscitation trauma trials are mentioned with no registry or publication source.", "The claim that hibernating rodents tolerate higher radiation doses is attributed only to older literature."]issues: ["The claim that hibernating rodents tolerate higher radiation doses is attributed only to older literature."]------ ```infobox```infoboxlines 54–60 → 54–6038 unchanged lines not shown
Therapeutic hypothermia is the only human intervention that reliably lowers metabolic rate, and it does so bluntly: cooling reduces oxygen consumption by roughly five to seven per cent for each degree Celsius. It is established practice in neonatal hypoxic-ischaemic encephalopathy, where cooling to about 33.5 °C for three days improves neurological outcomes. In adults after cardiac arrest the picture is less settled; the large TTM2 trial found no mortality benefit from targeting 33 °C compared with avoiding fever, and guidelines have shifted toward temperature control rather than deep cooling.[^ttm2]Therapeutic hypothermia is the only human intervention that reliably lowers metabolic rate, and it does so bluntly: cooling reduces oxygen consumption by roughly five to seven per cent for each degree Celsius. It is established practice in neonatal hypoxic-ischaemic encephalopathy, where cooling to about 33.5 °C for three days improves neurological outcomes. In adults after cardiac arrest the picture is less settled; the large TTM2 trial found no mortality benefit from targeting 33 °C compared with avoiding fever, and guidelines have shifted toward temperature control rather than deep cooling.[^ttm2] Cardiac surgery goes further. Deep hypothermic circulatory arrest cools patients to roughly 18 °C, allowing the heart to be stopped and circulation halted for tens of minutes while an aortic arch is repaired. Emergency preservation and resuscitation extends the same logic to exsanguinating trauma: replacing blood with cold saline to drop core temperature toward 10 °C, buying surgical time before resuscitation. Trials of this approach have been conducted in the United States and remain small.Cardiac surgery goes further. Deep hypothermic circulatory arrest cools patients to roughly 18 °C, allowing the heart to be stopped and circulation halted for tens of minutes while an aortic arch is repaired. Emergency preservation and resuscitation extends the same logic to exsanguinating trauma: replacing blood with cold saline to drop core temperature toward 10 °C, buying surgical time before resuscitation. A registered trial, run from the University of Maryland in patients whose hearts had stopped after penetrating injury, aimed at twenty subjects and has been terminated without posting results; the sponsor recorded that enrolment had been too slow and that the complexity of the intervention outweighed the low probability of benefiting a rare patient.[^eprcat] Accidental hypothermia indicates roughly where the outer bound of human tolerance sits. Among the best-documented survivals is a Norwegian skiing accident in which a woman was recovered with a core temperature of 13.7 °C after prolonged cardiac arrest and made a substantial neurological recovery on extracorporeal rewarming.[^gilbert2000] Such cases are rare, unplanned, and not a protocol.Accidental hypothermia indicates roughly where the outer bound of human tolerance sits. Among the best-documented survivals is a Norwegian skiing accident in which a woman was recovered with a core temperature of 13.7 °C after prolonged cardiac arrest and made a substantial neurological recovery on extracorporeal rewarming.[^gilbert2000] Such cases are rare, unplanned, and not a protocol. lines 77–82 → 77–8616 unchanged lines not shown
Adenosine receptor agonists have shown more consistent effects on thermoregulatory set point across species and remain an active line. None of this constitutes a drug that could be given to an astronaut.Adenosine receptor agonists have shown more consistent effects on thermoregulatory set point across species and remain an active line. None of this constitutes a drug that could be given to an astronaut. > [!caution] What the funded biostasis programmes have actually produced> DARPA's Biostasis programme has paid for metabolic-suppression work since 2018, and its published results run through *Xenopus* tadpoles and then out of the animal entirely. The delta-opioid compound SNC80 cut oxygen consumption in explanted porcine hearts to under half of vehicle control over six hours of perfusion, and reversibly suppressed metabolism in human gut and liver organ chips.[^sperry2024]> No intact large mammal has been placed in a hypometabolic state by any of this, and the perfused heart and the chip both remove the thing that makes a whole body hard: a defended set point, a circulation, and a brain. The step that would settle whether the torpor programme is latent in large mammals is a measurement of suppressed oxygen consumption, not merely lowered temperature, in a living pig or non-human primate. ## Why humans are hard## Why humans are hard Body size works against the whole project. Large animals cool and rewarm slowly, which makes any induction protocol a matter of hours, and slow rewarming is where much of the injury occurs. Below roughly 30 °C the human myocardium becomes prone to ventricular fibrillation, and defibrillation is unreliable at those temperatures. Cold produces coagulopathy, impaired platelet function, cold diuresis and electrolyte derangement, and suppresses immune responses at a time when a sedated, immobile patient is highly exposed to infection.Body size works against the whole project. Large animals cool and rewarm slowly, which makes any induction protocol a matter of hours, and slow rewarming is where much of the injury occurs. Below roughly 30 °C the human myocardium becomes prone to ventricular fibrillation, and defibrillation is unreliable at those temperatures. Cold produces coagulopathy, impaired platelet function, cold diuresis and electrolyte derangement, and suppresses immune responses at a time when a sedated, immobile patient is highly exposed to infection.lines 116–120 → 120–12633 unchanged lines not shown
[^blackstone2005]: `paper` Blackstone, E., Morrison, M., Roth, M.B. "H2S induces a suspended animation-like state in mice." *Science*, 2005. {Mice only; later attempts to reproduce comparable metabolic suppression in sheep and pigs did not succeed.}[^blackstone2005]: `paper` Blackstone, E., Morrison, M., Roth, M.B. "H2S induces a suspended animation-like state in mice." *Science*, 2005. {Mice only; later attempts to reproduce comparable metabolic suppression in sheep and pigs did not succeed.}[^toien2011]: `paper` Tøien, Ø. et al. "Hibernation in black bears: independence of metabolic suppression from body temperature." *Science*, 2011.[^toien2011]: `paper` Tøien, Ø. et al. "Hibernation in black bears: independence of metabolic suppression from body temperature." *Science*, 2011.[^gilbert2000]: `paper` Gilbert, M., Busund, R., Skagseth, A., Nilsen, P.Å., Solbø, J.P. "Resuscitation from accidental hypothermia of 13.7 °C with circulatory arrest." *The Lancet*, 2000. {A single case report of an accident and a rewarming, which records a survival rather than a reproducible protocol.}[^gilbert2000]: `paper` Gilbert, M., Busund, R., Skagseth, A., Nilsen, P.Å., Solbø, J.P. "Resuscitation from accidental hypothermia of 13.7 °C with circulatory arrest." *The Lancet*, 2000. {A single case report of an accident and a rewarming, which records a survival rather than a reproducible protocol.}[^sperry2024]: `paper` Sperry, M. M. et al. "Identification of pharmacological inducers of a reversible hypometabolic state for whole organ preservation." *eLife*, 2024. {The porcine work is on explanted hearts and limbs on perfusion, not on living pigs, and the human component is organ-on-chip tissue.}[^eprcat]: `trial` "Emergency Preservation and Resuscitation for Cardiac Arrest From Trauma." ClinicalTrials.gov NCT01042015, University of Maryland, Baltimore, updated 2026. {A registry record, so it documents the design, the termination and the sponsor's stated reason; no outcome data are posted.}[^ttm2]: `paper` Dankiewicz, J. et al. "Hypothermia versus Normothermia after Out-of-Hospital Cardiac Arrest." *New England Journal of Medicine*, 2021. {The comparison was cooling to 33 degrees against active fever avoidance, not against leaving temperature uncontrolled.}[^ttm2]: `paper` Dankiewicz, J. et al. "Hypothermia versus Normothermia after Out-of-Hospital Cardiac Arrest." *New England Journal of Medicine*, 2021. {The comparison was cooling to 33 degrees against active fever avoidance, not against leaving temperature uncontrolled.} removed, struck through added, underlinedLine numbers count the serialised markdown of each revision, frontmatter included.
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