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 .
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:
|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|
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.
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.
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:
- Conduction (conduction of heat from a warmer to a colder body)
- Convection (heat dissipation to the ambient air, is increased by wind, see also wind chill )
- Radiation (heat radiation from the human body)
- Respiration (loss of heat from exhaling heated air)
- 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 )
- Drowning accidents after cooling down, because of the higher thermal conductivity of water compared to air
- Falling into cold water, for example shipwrecked people after capsizing or other accidents
- Long stay in cold water, for example for water sports enthusiasts such as swimmers , surfers or canoeists . Children bathing in summer are particularly at risk.
- Break into the ice
- Long dives with insufficient thermal insulation due to neoprene or dry suits
In the mountains
- People buried by avalanches
- Accidental climbers , mountain hikers and winter sports enthusiasts after mountain accidents
- Wet, inadequate clothing (street clothing and cotton clothing instead of functional underwear , missing or too thin wetsuit in active water caves )
- Constantly low ambient temperature (in Central Europe 2 to 8 ° C depending on the altitude, even less in ice caves) with 100% humidity
- After accidents caused by complex, long-term rescue operations or waiting times until the cave rescue service arrives
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) .
- Sedentary behavior (also forced by neurological defects)
- Physical overexertion
- 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.
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
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 .
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 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.
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, 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 .
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