In medicine, heat damage is any health disorder that is caused by an increased ambient temperature for a long time. One differentiates the sunstroke , the heat cramp , the heat exhaustion , the heat exhaustion and heat stroke . The worst consequence can be heat death .
A sunstroke (also called insolation and heliosis ) is caused by prolonged direct sunlight on the head and neck area. The long-wave part of solar radiation, i.e. the thermal radiation of sunlight, is responsible for this damage. This leads to irritation of the meninges and tissue and to an inflammatory reaction, which in severe cases can turn into cerebral edema . Thus, a sunstroke is an isolated heat stroke of the head and therefore an exclusively thermal problem. The explanation that keeps appearing that the meninges are caused by the UV component of sunlight cannot be proven, since UV radiation does not penetrate the skin.
The sunstroke manifests itself as dizziness, headache, nausea and vomiting, ringing in the ears, drowsiness, inner restlessness, exhaustion, increased pulse rate and neck pain up to neck stiffness ( meningism ). Body temperature is almost always normal. In severe cases, it can lead to impaired consciousness up to unconsciousness and circulatory failure. Deaths have also been described.
Sunstroke can be prevented by wearing light-colored headgear. Small children in particular are at risk from sunstroke. The fontanelles and the sparse head hair of the first two years of life contribute to this. People with a bald head or a short hairstyle are also at increased risk.
A heat cramp caused by a lack of fluid and electrolytes (especially sodium chloride ) due to increased sweating. Above all, people who are not adapted to the temperatures ( acclimatization ) are affected , whose electrolyte concentration in sweat is significantly higher than in acclimatized people.
The symptoms are cramps (spasms) in the stressed muscles (different muscle groups of the extremities or the trunk), often painful, at normal body temperature. Circulatory problems or a rise in body temperature are atypical for heat cramps, they can indicate the presence of another or further heat damage. Spicy soups or electrolyte drinks usually improve the symptoms of heat cramps.
A heat exhaustion , even heat impotence or heat syncope is a malfunction of the circuit with a short unconsciousness due to heat-related expansion of the peripheral blood vessels.
To increase the heat dissipation through the skin, blood vessels expand in the periphery of the body. This leads to a massive redistribution of the blood volume in these areas, which "sinks" there. The heart is no longer offered enough blood to continue pumping it. The blood pressure is drastically reduced, the brain does not get enough blood and this leads to an unconsciousness that is usually only brief ( syncope ).
The main risk factors here are alcohol consumption and prolonged standing, especially in large crowds, where the possibility of heat dissipation through the skin is reduced. The symptom is mostly just the sudden onset of unconsciousness. Warning signs can include dizziness, weakness, nausea, and vomiting.
A heat exhaustion occurs by fluid and electrolyte loss without adequate supply from outside - and thus to a decrease in the extracellular fluid volume without increasing the body temperature (decrease of blood volume in the circulation). The consequence can be a failure of the circuit. This is intensified when the amount of blood circulating is reduced due to water loss. The critical limit is around 12% of body weight loss of water.
The symptoms of heat exhaustion are headache, dizziness, nausea, impaired consciousness and even loss of consciousness. The skin is reddened at first, then pale and damp. The pulse is fast, the blood pressure is low, and the breathing is fast and shallow. From around 40 ° C there is a risk of heat collapse, which is not a direct thermal damage to the body, but rather a failure of the circulation. As a result of the strong dilation of the skin vessels, there is a disproportion between the vascular capacity and the amount of blood circulating, resulting in a drop in blood pressure ( shock ) and ultimately unconsciousness.
The most important measure in first aid is to put the patient in the shade or a cool environment. If the patient is still conscious, he should be brought into the shock position. An unconscious patient must be placed in the stable side position if he is still breathing normally. If an unconscious patient does not breathe ( respiratory failure ), cardiopulmonary resuscitation must be carried out.
Heat stroke in humans
In the case of life-threatening heat stroke or heat stroke , the body temperature also rises to over 40 ° C (rectal temperature). This acute overheating of the body leads to brain edema . Symptoms are a body temperature similar to that of a very high fever, convulsions, a lack of perspiration due to an acute lack of water and clouding of consciousness , which can appear like tiredness and sleep. It can lead to brain damage. The causes are often physical overexertion in damp heat or staying in overheated, closed rooms.
In contrast to this (hyperpyretic) heat stroke, which is also known as hyperpyrexia , due to the accumulation of heat, the mostly harmless heat collapse (with or without a significantly increased core body temperature) is colloquially referred to as "heat stroke".
Heat stroke in horses
A horse that works at high temperatures but hardly or not at all sweats is on the verge of heat stroke. It is almost dry ( dehydrated ) and can no longer cool down by sweating. It now tries to give off heat through the lungs, so it breathes shallowly and intermittently. Muscle tremors often occur, caused by a lack of calcium , because a lot of calcium is excreted with the sweat. The blood thickens, so the heart has to work harder and faster. In the worst case, the horse collapses.
Heat stroke in dogs
In dogs, heat stroke is caused by a combination of decreased heat output and increased heat production. In particular, short-headed breeds are particularly sensitive to higher ambient temperatures. Symptoms are loss of consciousness up to a coma , ataxia , extreme panting, reddened and sometimes dry mucous membranes, profuse salivation, vomiting and, in the further course, often bloody diarrhea. A disseminated intravascular coagulopathy , cardiac arrhythmia or acute renal failure may occur. It is treated with active cooling and infusions. Since intestinal bacteria are often released into the bloodstream, antibiosis is always indicated. The mortality is very high at 50%. It mainly depends on how early the treatment is started.
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