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Classification according to ICD-10
R68.0 Hypothermia, not associated with low ambient temperature
P80.- Hypothermia in the newborn
T68 Hypothermia (accidental hypothermia)
ICD-10 online (WHO version 2019)

The hypothermia (from ancient Greek ὑπό Hypo , as ', and θερμός thermos , warm') or under temperature (by - also used interchangeably - subcooling ) is a condition with an abnormally low body temperature ( below normal body temperature ) of living organisms. It occurs after the body has been exposed to cold when its heat production has been less than the heat output over a longer period of time. Hypothermia, in people below 35 degrees Celsius, can damage health or cause death ( cold death ) through the failure of vital organ systems . With only local cold which leads to frostbite . In the event of accidents on the water or in the mountains, the helpers in the water rescue and mountain rescue service must always assume that the patient is hypothermic .

In medicine, (intended) mild therapeutic hypothermia or deep hypothermia is carried out in special cases in the operating theater, intensive care units and in neonatology .

Heat regulation of the body

The human body has the ability to keep its body temperature constant at around 37 ° C, even with fluctuations in the ambient temperature, which is known as thermoregulation . This normal value is subject to slight fluctuations depending on the activity and time of day. These include the increased release of heat during physical exertion and the production of heat through shivering cold , for example in the form of chills when a fever begins .

Stages and symptoms of hypothermia

The following (not uniformly used) stages of hypothermia or hypothermia are distinguished:

stage Body temperature Symptoms
Mild hypothermia 32-35 ° C Muscle tremors, separation of body shell / core, tachycardia , tachypnea , vasoconstriction , after some time: apathy , ataxia , impaired judgment
Moderate hypothermia 28-32 ° C Clouding of consciousness, bradycardia , dilated pupils , decreased gag reflex, stopping muscle tremors, hyporeflexia , hypotension , idiocy of cold
Severe hypothermia below 28 ° C Unconsciousness, cardiac arrest , decreased brain activity in the EEG , pulmonary edema , rigid pupils, cardiac arrhythmias , respiratory arrest

Mild hypothermia

The body tries to keep the core body temperature constant at a body temperature of 32 to 35 ° C (usually measured rectally) and produces heat through automated muscle tremors. In addition, the blood vessels in the extremities contract and reduce blood flow to the outer regions of the body ( centralization ). A bowl is created in which the cold blood remains. There is hardly any heat exchange between the shell and the body core.

Moderate hypothermia

The patient's consciousness becomes increasingly cloudy. This disturbance of consciousness can go so far that one speaks of cold idiocy . There is also a weakening of the reflexes (hyporeflexia) and the muscle tremors stop.

Severe hypothermia

If the temperature drops to less than 28 ° C, there is a loss of consciousness , an irregular and weakened pulse, and later to a respiratory and circulatory arrest due to cardiac arrhythmias . Light-rigid pupils and paralysis of the muscles also occur. With body temperatures below 28 ° C, it is difficult to determine clearly whether the hypothermic person is still alive or already dead. Breathing in this state can be too shallow and the pulse too slow and weak, especially in the extremities with little blood supply. Simple methods such as feeling the pulse or breathing are then not reliable. Occasionally the term apparent death is used in this state.


There are basically five causes of heat loss from the human body:

  1. Conduction (conduction of heat from a warmer to a colder body)
  2. Convection (heat dissipation to the ambient air, is increased by wind, see also wind chill )
  3. Radiation (heat radiation from the human body)
  4. Respiration (loss of heat from exhaling heated air)
  5. Perspiration (loss of heat through evaporation, e.g. from sweat)

In addition to a low air temperature , especially cold water and wind (see wind chill ) can increase the heat loss of the human body and, depending on the duration of exposure, lead to hypothermia. Typical situations in which hypothermia occurs are:

In water (hypothermia / hypothermia due to immersion )

In the mountains

In caves

Stay in a cold environment

  • Inappropriate or wet clothing
  • Falling asleep outdoors
  • Lying unconscious outdoors

In sport and especially in alpinism, where people are usually well equipped and prepared, frostbite is more likely to be caused by extreme temperatures and wind conditions, and hypothermia is more likely to be caused by an unforeseen, too long stay in moderately cold weather (0 to 5 ° C) .

Other causes

  • Diseases
  • Sedentary behavior (also forced by neurological defects)
  • Physical overexertion
  • shock
  • Alcohol consumption: Alcohol intensifies and accelerates hypothermia, as this is where the blood vessels in the skin expand and the body dissipates more heat to the environment.
  • Rare diseases: People with Shapiro syndrome show recurring defects in the thermoregulation of the hypothalamus . In any case, additional symptoms can be observed, such as sweating.

Immediate action

Rescue from the danger area

The rescue from the danger area must be carried out quickly, as the patient continues to cool down.

In principle, the patient should not be moved as much as possible. For example, the patient can be lifted horizontally out of the water on board a lifeboat with a basket stretcher or a so-called spine board .

If the temperature difference between the shell and the core of the body is too great, temperature equalization occurs when the patient is rewarmed or when he moves, and the core temperature can drop further ( afterdrop ). This can lead to so-called rescue death.


Follow the rescue chain:

  • Observe your own protection and secure the accident site
  • Make or initiate an emergency call
  • The patient gently bring out of the danger zone; if possible in a room at room temperature or at least in a place with no wind
  • Lay the patient flat and move little or, if possible, immobilize completely
  • Heat retention, d. H. Cover or wrap patients with woolen blankets. Never put a rescue blanket directly on the skin, it is then useless because of the lack of insulation. If necessary, apply a Hibler heat pack .
  • First, just warm up the body (according to the central circulation) using blankets etc. Not the extremities, as otherwise there is a risk of rescue death (see below).
  • Constant control of the vital functions .
  • Caring for the patient until the ambulance service arrives

Defense stage

Is the patient still in the defense stage?

  • then the patient's wet clothing can be carefully removed while the patient is shaking.
  • If conscious: give warm, sugared drinks (no alcohol, coffee or black tea).
  • Leisurely rewarming, e.g. B. with a hot water bottle

Stage of exhaustion or loss of consciousness

Is the patient in a state of exhaustion or paralysis?

  • then it must not be moved when undressing (remove clothing with scissors).
  • Only slow warm-up measures may be undertaken on the trunk.
  • if unconscious: stable lateral position
  • if there is no more breathing: cardiopulmonary resuscitation
  • then follow the points above

Follow-up action by the ambulance service

  • Absolute avoidance of the so-called rescue death: In the case of victims of ice falls, avalanches, etc., care must be taken not to raise the extremities above the level of the trunk, as the blood flowing back to the heart can cause a reflex cardiac arrest
  • Infusion of warmed NaCl or Ringer's solution . Also glucose administration is the concentration measurement is possible (perhaps even necessary)
  • Administration of oxygen and, if necessary, intubation
  • If lifeless: continue cardiopulmonary resuscitation
  • Transport to a maximum care hospital by rescue helicopter (if available)

Further treatment in the hospital

  • Continuation of cardiopulmonary resuscitation
  • Warming of the patient, also invasively through the use of a heart-lung machine


The resuscitation measures will continue during transport to the hospital and clinic. Medicines such as adrenaline and defibrillation only work from a certain body temperature. The reduced temperature also slows down the death of the brain cells .

Therefore the principle applies: Nobody is dead until they are warm and dead.


With death from hypothermia, Wischnewsky spots appear in the mucous membrane of the stomach .

Therapeutic hypothermia

Hypothermia reduces the metabolic activity and increases the ischemia tolerance of the tissues. In medicine, during major operations on the brain and on the heart (as was the case in the 1950s), an intended deep hypothermia ( deep hypothermia , also known as hypothermic cardiac arrest) is initiated. This is done by diverting the venous blood into an apparatus in which the blood is cooled down to a certain value below normal temperature and fed back into the bloodstream.

A milder therapeutic hypothermia after successful resuscitation performed because this reduces cerebral metabolism and reduced brain damage.

A study on the use of therapeutic hypothermia in stroke patients has been running at the University of Erlangen since 2012. By cooling down to 34 ° C to after ischemic stroke , the infarct area is reduced and the death of brain tissue can be prevented.

Science fiction

In medicine and futurology the use of cold sleep is also discussed to bridge epochs; People are put into cold sleep and therefore age much more slowly. After a few decades, the organism is activated again to full capacity. However, so far this is only a theory, in practice all such attempts have failed.

Extreme cases

Extreme, scientifically proven hypothermia is a body temperature of 13.7 ° C, which was measured in 1999 in an accident victim. Nevertheless, the victim Anna Bågenholm was able to be reanimated without permanent damage due to special circumstances, according to a report by the Spiegel .


Some fish and mammals remain frozen in cold weather. This natural cold sleep is called hibernation .

See also


  • J. Biem, N. Koehncke, D. Classen, J. Dosman: Out of the cold: management of hypothermia and frostbite. In: CMAJ. 2003 Feb 4; 168 (3), pp. 305-311. Review. PMID 12566336
  • Robert R. Kempainen, Douglas D. Brunette: The evaluation and management of accidental hypothermia. In: Respiratory Care. 2004 Feb; 49 (2), pp. 192-205. Review. PMID 14744270 ( PDF; 1 MB )
  • Lynne McCullough, Sanjay Arora: Diagnosis and treatment of hypothermia. In: Am Fam Physician. 2004 Dec 15; 70 (12), pp. 2325-2332. Review. PMID 15617296
  • Pschyrembel Clinical Dictionary . Founded by Willibald Pschyrembel. Edited by the publisher's dictionary editor. 255th edition. De Gruyter, Berlin 1986, ISBN 978-3110185348 , p. 757.

Web links

Wikibooks: Hypothermia First Aid  - Learning and Teaching Materials
Wiktionary: Hypothermia  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. warmth: Neonatology: hypothermia reduces damage in asphyxia. In: aerzteblatt.de . October 1, 2009, archived from the original on March 17, 2015 ; accessed on February 2, 2015 .
  2. Reinhard Larsen: Anesthesia and intensive medicine in cardiac, thoracic and vascular surgery. (1st edition 1986) 5th edition. Springer, Berlin / Heidelberg / New York et al. 1999, ISBN 3-540-65024-5 , pp. 100 and 164 (there four degrees of hypothermia).
  3. L. McCullough, S. Arora: Diagnosis and treatment of hypothermia. In: Am Fam Physician. 2004 Dec 15; 70 (12), pp. 2325-2332. Review. PMID 15617296
  4. ^ Mountaineering - The Freedom of the Hills . The Mountaineers Books, 2010, ISBN 978-1-59485-138-4 , pp. 592 .
  5. Periodic spontaneous hypothermia. In: OrphaNet
  6. Reinhard Larsen: Anesthesia and intensive medicine in cardiac, thoracic and vascular surgery. (1st edition 1986) 5th edition. Springer, Berlin / Heidelberg / New York et al. 1999, ISBN 3-540-65024-5 , pp. 97-106.
  7. Ernst Kern : Seeing - Thinking - Acting of a surgeon in the 20th century. ecomed, Landsberg am Lech 2000. ISBN 3-609-20149-5 , p. 109.
  8. Veronika Hackenbroch: Cardiac arrest at 28 degrees. Der Spiegel , issue 27/2010, July 5, 2010, accessed on December 12, 2011 .
  9. ^ Hypothermia after Cardiac Arrest Study Group: Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. In: N Engl J Med. , 2002 Feb 21, 346 (8), pp. 549-556. PMID 11856793
  10. D. Ahmadsey et al. a .: Tost, the mild therapeutic hypothermia - an evidence-based method with ILCOR class I recommendation to improve the neurological outcome after cardiac and circulatory arrest . (PDF) with further information.
  11. Hypothermia - An Option for a Stroke? In: aerztezeitung.de , September 2, 2011.
  12. Klaus von Brinkbäumer: A perfect accident . In: Der Spiegel . No. 8 , 2007, p. 64-68 ( online ).