In medicine, a burn ( Combustio , Kombustion , burn injury , burn trauma ) is tissue damage caused by excessive heat. This can be caused by hot objects, liquids ( scalding ), vapors or gases, the effects of flames and explosions, strong sunlight ( sunburn ), electrical current or friction. The burns primarily damage the skin (in which case it is burn wounds ) and mucous membrane . This must be distinguished from cold burns , a special form of frostbite that causes damage that is locally comparable to burning.
A burn injury that exceeds a certain level does not only have local consequences for the affected organism. Depending on the extent of the immediate damage, secondary circulatory shock and general inflammatory reactions of the body ( SIRS , sepsis ) can occur, which in the worst case are associated with a loss of function of organs initially not involved (e.g. acute kidney failure ). The entirety of these systemic disorders is called a burn disease .
The first textbook on burns appeared in Basel in 1607 under the title De Combustionibus . It was written by Fabricius Hildanus , who was the first to describe three degrees of burns. The first modern book on burn disease and its treatment, The Treatment of Burns and Skin Grafting by Haldor Sneve, appeared in 1905.
Causes and frequency
|Incidence of burns|
|over 65 years||10%|
Based on their cause, burns can be differentiated into those caused by flames; they make up a large proportion of 55% of cases, scalds caused by liquids and vapors (40%), and electrical and chemical fires (5%).
Mild burns occur with an annual incidence of 600 / 100,000 inhabitants, severe burns with 2–5 / 100,000 inhabitants.
The age of the patient plays a big role in the type of injury. In toddlers up to four years of age, scalds account for 70% of all injuries. This is due, on the one hand, to the lively motor development and the urge to explore (tearing down liquid containers from the stove or table) and, on the other hand, to the carelessness of the supervisor (e.g. bath water that is too hot). In older children and adolescents, the cause is often the improper handling of fire and flammable liquids (e.g. gasoline) or an electrical accident . Flame burns are most common in adults between the ages of 15 and 64; one third of the accidents are occupational accidents.
Tap water scalds
Depending on the user group, heated tap water should come out of the tapping point with a maximum of 38–45 ° C in order to avoid discomfort and scalding. The technical implementation is complicated by the fact that hot water pipes should be operated at 55–60 ° C in order to prevent the multiplication of legionella . Water at over 60 ° C can cause scalds within seconds, while water at 50 ° C only takes about two minutes.
Degree of combustion
According to the skin layers involved, it is classified into:
- 1st degree: reddening and slight swelling of the skin, pain, epidermis affected, completely reversible
- 2nd degree: blistering with a red-white background, severe pain, epidermis and dermis affected, complete healing (2a) or with scarring (2b, with deep dermis involvement)
- 3rd degree: black-and-white necrosis / blisters, no or only slight pain, as nerve endings are destroyed. Dermis and subcutis affected, irreversible
- 4th degree: charring, no pain, all skin layers and underlying bones / fasciae affected, irreversible
A burn of two to three degrees can lead to life-threatening hypovolemic shock from 10 percent burned body surface in adults and from 5 percent burned body surface in children . The tolerance is strongly dependent on the general condition and age of the patient.
Determination of the burned area
To determine the burn area in adults, the Wallace rule of nine , named after the Scottish surgeon AB Wallace, is used. In the case of children, due to the body proportions that are different from those of adults, a procedure with modified values must be used that is adapted to each age (e.g. according to Wichmann). These methods can be used to roughly determine what percentage of the body surface is burned.
|body part||Adult||Child (up to 5 years of age)||infant|
|hull||4 × 9 (36)%||2 × 16 (32)%||30%|
|poor||2 × 9 (18)%||2 × 9.5 (19)%||2 × 9 (18)%|
|legs||2 × 2 × 9 (36)%||2 × 17 (34)%||2 × 15 (30)%|
Another possibility is the calculation based on the rule of thumb that the palm of the hand including the patient's fingers is approx. 1% of the body surface.
The extent of skin and tissue damage is primarily decisive for the course of the burn disease. The proportion of the body surface (extent) and the severity of the local damage are important.
Measured by the extent, 15% burned body surface in adults and 10% burned body surface in children or 7.5% burned body surface in adults with inhalation trauma and 5% burned body surface in children with inhalation trauma are considered life-threatening (severe burn injuries).
The division into degrees of severity gives first indications of the threat posed by the burn. Very often other injuries or previous illnesses have to be taken into account in this assessment. Even with between 10 and 20 percent damaged skin surface, the risk can be so high that treatment should be carried out in a special clinic, a center for severe burns, if possible. The threatening sequelae can only be treated successfully in a department specially equipped for this in terms of personnel and equipment. The doctors in charge of the intensive care department for severe burn injuries require a special plastic intensive medical qualification certificate. The department needs its own operating theater. The risks associated with the transfer will almost always be lower than the complications threatening in a general hospital even with the best possible care there. In the Federal Republic of Germany, the coordination of admission to a center for burn injuries is carried out by the central contact point for the procurement of hospital beds for severely burned victims at the fire department in Hamburg.
Permanent temperature influences of over 40 ° C can overwhelm the organism's ability to compensate. If the amount of heat supplied exceeds a certain level, the heat cannot be dissipated by the normal heat exchange processes, such as radiation or removal of heat through the blood. At the molecular level, from 40 ° C, cellular proteins degenerate with a temporary loss of function. From 45 ° C, the thermal stress leads to denaturation and thus to the final structural and functional loss of the structural and functional proteins. The local changes are called coagulation necrosis in the clinical picture . The changed molecular structures have a toxic , antigenic and immunomodulatory effect .
In the case of partial exposure to heat, skin damage occurs after the following exposure times:
- between 45 ° C and 51 ° C within minutes
- between 51 ° C and 70 ° C within seconds
- over 70 ° C in fractions of a second
According to Jackson, the local changes in a burn wound are divided into three zones, see table:
|Coagulation zone||Core of the thermal damage, destruction of the cell structures due to the denaturation of proteins|
|Stasis zone||Impairment of cell functions, no permanent destruction of cell structures, but restricted blood flow (capillary perfusion) and a tendency to permanent damage from pathological immune processes (mediator release) and oxygen deficiency (hypoxia).|
|Zone of hyperemia||not directly affected by the thermal damage, part of the local compensation mechanism with increased blood flow (hyperemia) to remove the heat|
The tissue of the coagulation zone is permanently destroyed.
The stasis zone is of the greatest therapeutic interest. Three characteristics are essential:
- Uninterrupted supply of heat leads to denaturation of the proteins, i.e. to the so-called deepening of the coagulation zone .
- The pathological immune processes initiate immune reactions of the whole organism.
- The process is reversible and normal local function can be regained.
The aim of immediate therapy is to reduce the stasis zone. For this purpose, heat is removed from the tissue by treatment with cold water.
In the untreated course of the disease, swelling, blistering and reddening become visible. The fundamental pathophysiological mechanism for this is extravasation (leakage of fluid from the interior of the vessels into the surrounding tissue) through endothelial damage (capillary leak) in the stasis zone and vessel widening (hyperemia zone).
Effect on the whole organism
Mediator substances are released from the damaged area (stasis zone) , which trigger and maintain a generalized immune reaction of the organism. These phenomena, which are already visible in the early course of the burn disease, cause:
- Activation of the coagulation cascade
- Activation of the complement system
- Platelet activation and aggregation (platelets)
- Direct and indirect endothelial damage (damage to the inner skin of blood vessels)
- Granulocyte Immigration and Activation
- Macrophage immigration (scavenger cell migration)
- Immunomodulation by interleukins
For the first minutes and hours after the injury, the endothelial damage seems to be of particular concern. Here is referred to the formation of a capillary leak (capillary leak) that enables the uncontrolled escape of water from the blood vasculature into the surrounding tissue and the development of an edema can result.
The circulating blood volume thus decreases. The fluid displacements cause such high volume losses in the blood vessels that, if left untreated, circulatory reactions (falling blood pressure, increase in heart rate) and, in the most severe case, circulatory shock occur. For example, if the body surface area is 40% burned, the plasma volume falls to 25% of the initial value.
The peculiarity of volume loss through the capillary leak is that only blood plasma (water with dissolved substances such as proteins) is released into the tissue, the solid components of the blood (blood cells) remain in the vascular system. This has two consequences:
- The proportion of solid blood components increases (the hematocrit value increases), which leads to a higher viscosity of the blood.
- Dissolved proteins are lost in the circulating blood (the oncotic pressure drops). This process leads to further loss of fluid from the vessels.
By increasing the viscosity, the flow properties of the blood are worsened, especially in the capillary area. Volume deficiency and increased hematocrit are important causes of organ failure (particularly important here: acute kidney failure ) and circulatory shock .
The accumulation of fluid in the tissue leads to swelling of loose tissue (soft tissue edema). This process takes place in the entire organism. It is not uncommon for 20–30 liters to be stored after appropriate treatment (see below). The resulting increase in pressure in the tissue, however, also promotes circulatory disorders and lymph drainage disorders, which disrupts the nutrition of the tissue concerned.
In the case of severe burns, one has to assume that SIRS will develop based on the inflammatory reaction and the release of inflammatory mediators . The germ colonization (infection) of the burned areas and the penetration of the pathogens into the organism lead to sepsis .
Measures for the local treatment of burns (e.g. with mud and cow dung) are already in the Ebers Papyrus in 1550 BC. Occupied. Cold applications were used in Arabic medicine and a successful cold application using ice, published by the British surgeon James Earle (1755-1817) in 1799, gained importance. In contrast, the famous surgeon Ambroise Paré treated burns with heat in the 16th century (by "burning out"). In 1850, the surgeon James Syme was the first to set up a special clinic for burn injuries, the Burn House of the Royal Infirmary in Surgeons Square in Edinburgh . Even if therapeutic approaches with the generous administration of beverages and salt infusions were already being pursued in the 19th century, shock treatment did not become the focus of treatment until the 1930s. In 1952 EI Evans developed a formula for fluid replacement based on the extent of the burned body surface and body weight. Since the 1980s, methods for covering defects with skin substitutes grown in the laboratory for epidermal transplantation have been developed. Since the treatment of severe burns is extremely complex and difficult, centers have specialized in its treatment.
First aid, cooling
Small burns should be cooled for two minutes immediately after removing the heat source in order to relieve the pain of the person affected and to prevent the affected area from spreading through hot tissue. To cool small burns, use lukewarm, but not cold, tap water . Chilling with ice carries the risk of causing frostbite and should be avoided. You should also only use low-germ water (ideally: tap water) to prevent infections . If the burn is on the face, cooling should be done with damp towels. The well-being of the person concerned must always be taken into account when cooling. If large burns were cooled, the body would lose too much heat, which is prognostically very unfavorable. The cooling of large burns carries the risk of hypothermia. If the area concerned is larger than two A4 pages, it should therefore not be cooled.
The study situation on the subject of cooling is very vague, there are hardly any controlled studies that have proven a positive effect. The only positive result of cooling is an analgesic (pain-relieving) effect, which makes cooling appear sensible for small burns.
Burned clothing or other objects burned into the skin are removed in specialist clinics and remain with the person concerned until then. Burn wounds must first be covered loosely and free of germs and the person affected should be covered. If the person concerned becomes unconscious, the basic first aid measures apply ( stable lateral position , resuscitation ). After cooling, the burn wound should be covered with a sterile , if possible non- fluffy wound dressing (ideally a metal wound dressing) and presented to the doctor. Oil, flour or other household remedies must not be applied to the burn wound. Special gel or ointment supplies are only to be applied by doctors and are not part of first aid in the event of burns.
If the heat also gets into the airways through inhalation, it is called an inhalation trauma . Because of the rapidly increasing swelling of the mucous membranes and the risk of suffocation, the airway must be secured with a ventilation tube or an incision in the windpipe . The swelling of the mucous membranes should not be treated with cortisone , since the weakening of the immune system by cortisone increases the risk of infections in a burned victim. Nebulized medication can be used to treat the irritated bronchi: Beta-2 sympathomimetics expand the irritated bronchi, accelerate the repair of the mucous membrane and improve the breakdown of excess mucus. Heparin and antithrombin III in nebulised form can reduce the formation of bronchial stiffening caused by fibrin .
From a burned body surface area of 20% (10% in children), the effect of the capillary leak plays a decisive role in the initial course of the burn disease (see section “Effect on the whole organism”).
The most important goal in the first minutes and hours of therapy is to increase blood volume by infusing fluid. The assessment of the amount and the type of means requires a brief preliminary consideration: At the time of these therapeutic measures, it must be assumed that the capillary leak is maintained by active immune processes. Protein-rich blood plasma is constantly being lost in the tissue, as the damaged epithelium is not an effective barrier for the large protein molecules. On the one hand, there is a considerable loss of blood volume, which has to be compensated for by administering considerable amounts of water, especially in the first minutes and hours after the injury. On the other hand, there is a significant increase in the colloid osmotic pressure in the tissue and thus a perpetuation of the process, since the high colloid osmotic pressure binds water in the tissue.
Crystalloid infusion solutions such as Ringer's acetate are the drug of choice. Crystalloid solutions initially have the disadvantage that they enter the tissue very quickly. However, since they do not build up any additional pressure in the tissue and the water can be quickly mobilized into the vascular system after the epithelium has healed, they have decisive advantages in the course of therapy. Colloidal solutions are contraindicated because they increase the colloid osmotic pressure in the tissue, accelerate the formation of edema and remove fluid from the body (rebound effect).
According to the Parkland formula , 4 ml of crystalloid fluid per kg of body weight per percent of the burned body surface area must be infused in the first 24 hours after the injury (4 × body weight in kg ×% burned body surface area = ml in 24 h). Half of this is given in the first eight hours and a quarter in each of the next eight hours and the following eight hours (also called Baxter's rule and Baxter's Parkland formula ).
The calculation using this formula is a guide, but should be adapted to the individual case. The amount of agent to be infused is based on parameters of body function. These include the heart index, the amount of oxygen in the blood, vascular resistance and urine production.
Therapy of sepsis and multiple organ failure
In addition to the development of infections (which can be treated with antibiotics if necessary) and severe sepsis , the effects of volume depletion, tissue edema and the immune reaction threaten the occurrence of
- Cardiovascular failure,
- acute respiratory failure ,
- acute kidney failure ,
- Liver failure and
- intra-abdominal compartment syndrome .
The burned vital tissue is a good entry point for microorganisms such as bacteria and fungi. In addition, the dead tissue initiates and sustains the harmful inflammatory processes that make up the severity of the burn disease. As long as the damaged tissue has not been removed, the cause of the above-mentioned sepsis and multiple organ failure has not been eliminated.
For this reason, the earliest possible surgical and complete removal of non-vital tissue, the so-called debridement , is indicated. This goes so far that the cosmetic and functional results of these interventions often take a back seat in order to be able to interrupt the progression of the burn disease.
In convalescence, plastic surgery methods come to the fore.
The aim is to start over again as quickly as possible. 12,000 to 24,000 kJ / day (~ 2850–5700 kcal) and adequate vitamin intake are important. The patients have a greatly increased basal metabolic rate. In the acute phase, a combination of parenteral nutrition and enteral nutrition is used with the aim of exclusively enteral nutrition .
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