Hypothermia

Definition / introduction

Synonym: Hypothermia

Hypothermia can affect individual parts of the body as well as the entire body. Exposed parts of the body such as hands, feet, ears and the nose (acra) are particularly at risk from hypothermia. If the entire body cools down, it is referred to as hypothermia if the core body temperature is below 36 ° C. Permanent hypothermia can lead to frostbite and a life-threatening condition.

Thermoregulation

The body is normally able to keep its temperature in a range of Stable at 36.4 ° C - 37.4 ° C to keep. in the The course of the day fluctuates body temperature within these limits, being during the night the lowest values can be achieved. In the early morning the body temperature rises again; sinks the core body temperature too strong off, the body begins with the Counter regulation. This includes that in particular the Skin and extremities (arm and leg) with less blood are supplied. In extreme cases only the vital organs supplied with blood and thus kept warm (centralization). Additionally, the body tries through what is called Shivering, i.e. a rhythmic contraction of the thin muscles in the skin, To produce heat.

Newborn are due to their unfavorable ratio of body surface area to body volume particularly at risk cool down and therefore have a layer of brown adipose tissuewhich an adult no longer has. This brown fat can be especially good for that Heat production and protects the newborn from dangerous hypothermia.

causes

Exceeds the Heat emission those of the body produced heat, the core body temperature drops. The body is no longer able to compensate for the loss of heat and it can ultimately lead to hypothermia. Typically a decreased core body temperature occurs prolonged stay in a cold environment without adequate clothing.

There are five causes that can lead to heat loss:

1. convection - The body heat is given off to the colder ambient air; the effect increases with wind.
2. Conduction - The body heat is given off to a colder body and the bodies continue to adjust their temperatures to one another until they are even.
3. respiration - The body loses heat when breathing, as warmed air leaves the body and cold air flows in when breathing in, which in turn has to be heated.
4. Perspiration - Due to the constant evaporation of liquid on the body surface, the body cools down. At high outside temperatures, the body promotes this loss of heat through increased sweating; at cold temperatures, however, the cooling is unintentionally accelerated.
5. radiation - As with any energy-producing process, the body loses heat in the form of thermal radiation. Clothing can act like an insulating material and hold back heat radiation.

Risk factors

Particularly at risk are suffering from hypothermia

1. Old and sick people (especially Dementia sufferers)
2. Miners and divers
3. homeless people
4. Under- or malnourished people
5. Drunk people
6. People with thermoregulatory disorders
7. diabetic and thyroid patients, as their temperature sensation is disturbed
8. Newborn

Symptoms and Stages

The symptoms of hypothermia depend on the extent of hypothermia; the further the core body temperature drops, the more life-threatening the condition becomes for the body.

Hypothermia is divided into four phases, which are composed of the degree of hypothermia and the physical reactions of the hypothermic.

• Phase 1 = defense stage: At this stage, the body temperature is between 34.0 and 36.0 ° C. The body tries to produce heat by shivering and to maintain the lowered temperature. The blood vessels contract (constriction) so that the extremities in particular are supplied with less blood. This creates a centralized blood circulation and the narrowed vessels lead to an increase in blood pressure. In addition, the heartbeat is increased and breathing accelerates. An unconsciousness does not yet occur at this stage.

• Phase 2 = stage of exhaustion: The body temperature is between 30.0 -34.0 ° C. At this stage the body already gives up the attempt to maintain the body temperature by counterregulating it. There is no more shivering and the hypothermic patient becomes increasingly indifferent and disoriented. The heart no longer tries to keep the core warm by increasing the number of beats, and the blood pressure drops. The pupils are dilated and the reflexes are reduced, especially the gag reflex. The body begins to become stiff overall, making it difficult to move the joints. Therefore, when locating a hypothermic person, as few movements as possible should be performed so as not to cause injuries.

• Phase 3 = paralysis stage: The body temperature has dropped to 27.0 to 30.0 ° C. The patient becomes unconscious and physical reactions in the form of a defense only occur in response to a pain stimulus. There is a possibility of falling into a coma. The blood pressure and the heart rate continue to drop and cardiac arrhythmias occur that can even lead to fatal ventricular fibrillation.

• Phase 4 = apparent death stage: The body temperature at this stage is only 24.0 to 27.0 ° C. The unconscious person no longer reacts even to pain stimuli and is in a coma. The pupils are dilated and no longer react to a light stimulus. The brain activity is measurably reduced. Both pulse and breathing can no longer be determined with certainty, so that a clear decision as to whether death has already occurred is hardly possible. In this state, respiratory or circulatory arrest is possible at any time.

Diagnosis

Hypothermia is mainly caused by the core body temperature measured rectally diagnosed. For this purpose, special thermometers are required that can also record low temperatures. One measurement under the tongue is also possible, the measured values ​​are, however 0.3-0.5 ° C below the rectal temperature. The frequently used temperature measurement in ear is in hypothermic people not possible, since the blood supply to the ears is greatly reduced and no measurement results can be determined.

In addition, the Vital signs – Blood pressure, pulse, oxygen saturation - and the General condition consulted for diagnosis. It will always be a EKG written to be cold-related Cardiac arrhythmias and exclude ECG changes. Also is a Blood diagnostics important to the oxygen levels in the blood Sugar content and to determine some other parameters.

therapy

The focus of therapy for hypothermia is Rewarming of the body; there are three approaches to this.

• The passive rewarming: The hypothermic is in Reflecting thermal radiation Foils or blankets wrapped and warms with his self-produced heatthat can no longer be emitted. This shape can increase the temperature by 0.1 - 3.0 ° C in one hour can be achieved.

• Active external rewarming: It will special thermal blankets and Radiant heater used for warming up. So can an increase in body temperature around 1.0 to 4.0 ° C can be achieved.

• The active core - rewarming: The aim of this form of therapy is the body from the inside out by means of the gift of warmed infusions to warm up. With severe hypothermia, a dialysis be performed; it will blood warmed outside the body and returned to the bloodstream. This allows the body temperature within one hour around up to 10 ° C increased become.

With all forms of rewarming, care should be taken not to do it too quickly, as this can lead to severe side effects, how Cardiac arrhythmias or one Cardiac arrest can come. In addition to rewarming, a revival to be necessary.

Basically: Nobody is dead until they are warm and dead!

forecast

In many cases stay little to no damage persist after hypothermia if therapy could be started on time. The longer the hypothermia has persisted, the more likely it is Long-term consequences how irreversible Frostbite, Nerve damage or Restrictions on movement. are Cardiac arrhythmias occurred, permanent damage to the heart's action can also occur.

Therapeutic hypothermia

The conscious cooling the body is used in medicine when one is too low blood supply, especially the brain is to be expected, for example at Heart or brain surgery, after revival or at Strokes.

The reason for this is that one is hypothermic decreased metabolism and the cells therefore need fewer nutrients and, above all, less oxygen to survive. The brain in particular benefits from a slight hypothermia of 32 - 34 ° Cbecause less annoy suffer from reduced blood supply and be damaged. The fewer the nerves that die off due to insufficient supply, the more less permanent damage the patient will be carried away.

Lie serious physical injuries or a high blood loss before, this method cannot be used because the Risk of severe wound healing disorders too great is. The use of therapeutic hypothermia carries the risk of Cardiac arrhythmias. The procedure will meanwhile also with newborns used who suffered from an insufficient supply of oxygen before or during the birth and are therefore at risk of brain damage.