出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/05/07 13:35:08」(JST)
| Burn | |
|---|---|
| Classification and external resources | |
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Second-degree burn of the hand
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| ICD-10 | T20–T31 |
| ICD-9 | 940–949 |
| DiseasesDB | 1791 |
| MedlinePlus | 000030 |
| eMedicine | article/1278244 |
| MeSH | D002056 |
A burn is a type of injury to flesh or skin caused by heat, electricity, chemicals, friction, or radiation.[1] Burns that affect only the superficial skin are known as superficial or first-degree burns. When damage penetrates into some of the underlying layers, it is a partial-thickness or second-degree burn. In a full-thickness or third-degree burn, the injury extends to all layers of the skin. A fourth-degree burn additionally involves injury to deeper tissues, such as muscle or bone.
The treatment required depends on the severity of the burn. Superficial burns may be managed with little more than simple pain relievers, while major burns may require prolonged treatment in specialized burn centers. Cooling with tap water may help relieve pain and decrease damage; however, prolonged exposure may result in low body temperature. Partial-thickness burns may require cleaning with soap and water, followed by dressings. It is not clear how to manage blisters, but it is probably reasonable to leave them intact. Full-thickness burns usually require surgical treatments, such as skin grafting. Extensive burns often require large amounts of intravenous fluids because the subsequent inflammatory response will result in significant capillary fluid leakage and edema. The most common complications of burns are related to infection.
While large burns can be fatal, modern treatments developed since 1960 have significantly improved the outcomes, especially in children and young adults.[2] Globally, about 11 million people seek medical treatment, and 300,000 die from burns each year.[3] In the United States, approximately 4% of those admitted to a burn center die from their injuries.[4] The long-term outcome is primarily related to the size of burn and the age of the person affected.
The characteristics of a burn depend upon its depth. Superficial burns cause pain lasting two or three days, followed by peeling of the skin over the next few days.[5][6] Individuals suffering from more severe burns may indicate discomfort or complain of feeling pressure rather than pain. Full-thickness burns may be entirely insensitive to light touch or puncture.[6] While superficial burns are typically red in color, severe burns may be pink, white or black.[6] Burns around the mouth or singed hair inside the nose may indicate that burns to the airways have occurred, but these findings are not definitive.[7] More worrisome signs include: shortness of breath, hoarseness, and stridor or wheezing.[7] Itchiness is common during the healing process, occurring in up to 90% of adults and nearly all children.[8] Numbness or tingling may persist for a prolonged period of time after an electrical injury.[9] Burns may also produce emotional and psychological distress.[3]
| Type[10] | Layers involved | Appearance | Texture | Sensation | Healing Time | Prognosis | Example |
|---|---|---|---|---|---|---|---|
| Superficial (First-degree) | Epidermis[5] | Red without blisters[10] | Dry | Painful[10] | 5–10 days[10][11] | Heals well;[10] Repeated sunburns increase the risk of skin cancer later in life[12] | |
| Superficial partial thickness (Second-degree) | Extends into superficial (papillary) dermis[10] | Redness with clear blister. Blanches with pressure.[10] | Moist[10] | Very painful[10] | less than 2–3 weeks[6][10] | Local infection/cellulitis but no scarring typically[6] | |
| Deep partial thickness (Second-degree) | Extends into deep (reticular) dermis[10] | Yellow or white. Less blanching. May be blistering.[10] | Fairly dry[6] | Pressure and discomfort[6] | 3–8 weeks[10] | Scarring, contractures (may require excision and skin grafting)[6] | |
| Full thickness (Third-degree) | Extends through entire dermis[10] | Stiff and white/brown[10] No blanching[6] | Leathery[10] | Painless[10] | Prolonged (months) and incomplete[10] | Scarring, contractures, amputation (early excision recommended)[6] | |
| Fourth-degree | Extends through entire skin, and into underlying fat, muscle and bone[10] | Black; charred with eschar | Dry | Painless | Requires excision[10] | Amputation, significant functional impairment and, in some cases, death.[10] |
Burns are caused by a variety of external sources classified as thermal (heat-related), chemical, electrical, and radiation.[13] In the United States, the most common causes of burns are: fire or flame (44%), scalds (33%), hot objects (9%), electricity (4%), and chemicals (3%).[14] Most (69%) burn injuries occur at home or at work (9%),[4] and most are accidental, with 2% due to assault by another, and 1-2% resulting from a suicide attempt.[3] These sources can cause inhalation injury to the airway and/or lungs, occurring in about 6%.[15]
Burn injuries occur more commonly in the poor. Smoking is a risk factor, although alcohol use is not. Fire-related burns are generally more common in colder climates.[3] Specific risk factors in the developing world include cooking with open fires or on the floor[1] as well as developmental disabilities in children and chronic diseases in adults.[16]
In the United States, fire and hot liquids are the most common causes of burns.[15] Of house fires that result in death, smoking causes 25% and heating devices cause 22%.[1] Almost half of injuries are due to efforts to fight a fire.[1] Scalding is caused by hot liquids or gases and most commonly occurs from exposure to hot drinks, high temperature tap water in baths or showers, hot cooking oil, or steam.[17] Scald injuries are most common in children under the age of five[10] and, in the United States and Australia, this population makes up about two-thirds of all burns.[15] Contact with hot objects is the cause of about 20-30% of burns in children.[15] Generally, scalds are first- or second-degree burns, but third-degree burns may also result, especially with prolonged contact.[18] Fireworks are a common cause of burns during holiday seasons in many countries.[19] This is a particular risk for adolescent males.[20]
Chemicals cause from 2 to 11% of all burns and contribute to as many as 30% of burn-related deaths.[21] Chemical burns can be caused by over 25,000 substances,[10] most of which are either a strong base (55%) or a strong acid (26%).[21] Most chemical burn deaths are secondary to ingestion.[10] Common agents include: sulfuric acid as found in toilet cleaners, sodium hypochlorite as found in bleach, and halogenated hydrocarbons as found in paint remover, among others.[10] Hydrofluoric acid can cause particularly deep burns which may not become symptomatic until some time after exposure.[22] Formic acid may cause the breakdown of significant numbers of red blood cells.[7]
Electrical burns or injuries are classified as high voltage (greater than or equal to 1000 volts), low voltage (less than 1000 volts), or as flash burns secondary to an electric arc.[10] The most common causes of electrical burns in children are electrical cords (60%) followed by electrical outlets (14%).[15] Lightning may also result in electrical burns.[23] Risk factors for being struck include involvement in outdoor activities such as mountain climbing, golf and field sports, and working outside.[9] Mortality from a lightning strike is about 10%.[9]
While electrical injuries primarily result in burns, they may also cause fractures or dislocations secondary to blunt force trauma or muscle contractions.[9] In high voltage injuries, most damage may occur internally and thus the extent of the injury cannot be judged by examination of the skin alone.[9] Contact with either low voltage or high voltage may produce cardiac arrhythmias or cardiac arrest.[9]
Radiation burns may be caused by protracted exposure to ultraviolet light (such as from the sun, tanning booths or arc welding) or from ionizing radiation (such as from radiation therapy, X-rays or radioactive fallout).[24] Sun exposure is the most common cause of radiation burns and the most common cause of superficial burns overall.[25] There is significant variation in how easily people sunburn based on their skin type.[26] Skin effects from ionizing radiation depend on the amount of exposure to the area, with hair loss seen after 3 Gy, redness seen after 10 Gy, wet skin peeling after 20 Gy, and necrosis after 30 Gy.[27] Redness, if it occurs, may not appear until some time after exposure.[27] Radiation burns are treated the same as other burns.[27] Microwave burns occur via thermal heating caused by the microwaves.[28] While exposures as short as two seconds may cause injury, overall this is an uncommon occurrence.[28]
In those hospitalized from scalds or fire burns, 3–10% are from assault.[29] Reasons include: child abuse, personal disputes, spousal abuse, elder abuse, and business disputes.[29] An immersion injury or immersion scald may indicate child abuse.[18] It is created when an extremity or the lower body (buttock or perineum) is held under the surface of hot water.[18] It typically produces a sharp upper border and is often symmetrical.[18] Other high-risk signs of potential abuse include: circumferential burns, the absence of splash marks, a burn of uniform depth, and association with other signs of neglect or abuse.[30]
Bride burning, a form of domestic violence, occurs in some cultures such as India where a woman is burned due to what the husband or his family consider to be an inadequate dowry.[31][32] In Pakistan, acid burns represent 13% of intentional burns, and are frequently related to domestic violence.[30] Self-immolation (setting oneself on fire as a form of protest) is also relatively common among Indian women.[3]
At temperatures greater than 44 °C (111 °F), proteins begin losing their three-dimensional shape and start breaking down.[33] This results in cell and tissue damage.[10] Many of the direct health effects of a burn are secondary to disruption in the normal functioning of the skin.[10] They include disruption of the skin's sensation, ability to prevent water loss through evaporation, and ability to control body temperature.[10] Disruption of cell membranes causes cells to lose potassium to the spaces outside the cell and to take up water and sodium.[10]
In large burns (over 30% of the total body surface area), there is a significant inflammatory response.[34] This results in increased leakage of fluid from the capillaries,[7] and subsequent tissue edema.[10] This causes overall blood volume loss, with the remaining blood suffering significant plasma loss, making the blood more concentrated.[10] Poor blood flow to organs such as the kidneys and gastrointestinal tract may result in renal failure and stomach ulcers.[35]
Increased levels of catecholamines and cortisol may result in a hypermetabolic state which can last for years.[34] This is associated with increased cardiac output, metabolism, a fast heart rate, and poor immune function.[34]
Burns can be classified by depth, mechanism of injury, extent, and associated injuries. The most commonly used classification is based on the depth of injury. The depth of a burn is usually determined via examination, although a biopsy may also be used.[10] It may be difficult to accurately determine the depth of a burn on a single examination and repeated examinations over a few days may be necessary.[7] In those who have a headache or are dizzy and have a fire-related burn, carbon monoxide poisoning should be considered.[36] Cyanide poisoning should also be considered.[7]
The size of a burn is measured as a percentage of total body surface area (TBSA) affected by partial thickness or full thickness burns.[10] First-degree burns that are only red in color and are not blistering are not included in this estimation.[10] Most burns (70%) involve less than 10% of the TBSA.[15]
There are a number of methods to determine the TBSA, including the "rule of nines", Lund and Browder charts, and estimations based on a person's palm size.[5] The rule of nines is easy to remember but only accurate in people over 16 years of age.[5] More accurate estimates can be made using Lund and Browder charts, which take into account the different proportions of body parts in adults and children.[5] The size of a person's handprint (including the palm and fingers) is approximately 1% of their TBSA.[5]
| Minor | Moderate | Major |
|---|---|---|
| Adult <10% TBSA | Adult 10–20% TBSA | Adult >20% TBSA |
| Young or old < 5% TBSA | Young or old 5–10% TBSA | Young or old >10% TBSA |
| <2% full thickness burn | 2–5% full thickness burn | >5% full thickness burn |
| High voltage injury | High voltage burn | |
| Possible inhalation injury | Known inhalation injury | |
| Circumferential burn | Significant burn to face, joints, hands or feet | |
| Other health problems | Associated injuries |
In order to determine the need for referral to a specialized burn unit, the American Burn Association devised a classification system. Under this system, burns can be classified as major, moderate and minor. This is assessed based on a number of factors, including total body surface area affected, the involvement of specific anatomical zones, the age of the person, and associated injuries.[36] Minor burns can typically be managed at home, moderate burns are often managed in hospital, and major burns are managed by a burn center.[36]
Historically, about half of all burns were deemed to be preventable.[1] Burn prevention programs have significantly decreased rates of serious burns.[33] Preventive measures include: limiting hot water temperatures, smoke alarms, sprinkler systems, proper construction of buildings, and fire-resistant clothing.[1] Experts recommend setting water heaters below 48.8 °C (119.8 °F).[15] Other measures to prevent scalds include using a thermometer to measure bath water temperatures, and splash guards on stoves.[33] While the effect of the regulation of fireworks is unclear, there is tentative evidence of benefit[37] with recommendations including the limitation of the sale of fireworks to children.[15]
Resuscitation begins with the assessment and stabilization of the person's airway, breathing and circulation.[5] If inhalation injury is suspected, early intubation may be required.[7] This is followed by care of the burn wound itself. People with extensive burns may be wrapped in clean sheets until they arrive at a hospital.[7] As burn wounds are prone to infection, a tetanus booster shot should be given if an individual has not been immunized within the last five years.[38] In the United States, 95% of burns that present to the emergency department are treated and discharged; 5% require hospital admission.[3] With major burns, early feeding is important.[34] Hyperbaric oxygenation may be useful in addition to traditional treatments.[39]
In those with poor tissue perfusion, boluses of isotonic crystalloid solution should be given.[5] In children with more than 10-20% TBSA burns, and adults with more than 15% TBSA burns, formal fluid resuscitation and monitoring should follow.[5][40][41] This should be begun pre-hospital if possible in those with burns greater than 25% TBSA.[40] The Parkland formula can help determine the volume of intravenous fluids required over the first 24 hours. The formula is based on the affected individual's TBSA and weight. Half of the fluid is to be administered over the first 8 hours, and the remainder given over the following 16 hours. The time frame is calculated from the time at which the burn occurred, and not from the time at which fluid resuscitation was begun. Children require additional maintenance fluid that includes glucose.[7] Additionally, those with inhalation injuries require more fluid.[42] While inadequate fluid resuscitation may cause problems, over-resuscitation can also be detrimental.[43] The formulas are only a guide, with infusions ideally tailored to a urinary output of >30 mL/h in adults or >1mL/kg in children and mean arterial pressure greater than 60 mmHg.[7]
While lactated Ringer's solution is often used, there is no evidence that it is superior to normal saline.[5] Crystalloid fluids appear just as good as colloid fluids, and as colloids are more expensive they are not recommended.[44] Blood transfusions are rarely required.[10] They are typically only recommended when the hemoglobin level falls below 60-80 g/L (6-8 g/dL)[45] due to the associated risk of complications.[7] Intravenous catheters may be placed through burned skin if needed or intraosseous infusions may be used.[7]
Early cooling (within 30 minutes of the burn) reduces burn depth and pain, but care must be taken as over-cooling can result in hypothermia.[5][10] It should be performed with cool water 10–25 °C (50.0–77.0 °F) and not ice water as the latter can cause further injury.[5][33] Chemical burns may require extensive irrigation.[10] Cleaning with soap and water, removal of dead tissue, and application of dressings are important aspects of wound care. If intact blisters are present, it is not clear what should be done with them. Some tentative evidence supports leaving them intact. Second-degree burns should be re-evaluated after two days.[33]
In the management of first- and second-degree burns, little quality evidence exists to determine which type of dressing should be used.[46][47] It is reasonable to manage first-degree burns without dressings.[33] While topical antibiotics are often recommended, there is little evidence to support their use.[48] Silver sulfadiazine (a type of antibiotic) is not recommended as it potentially prolongs healing time.[47] There is insufficient evidence to support the use of dressings containing silver[49] or negative-pressure wound therapy.[50]
Burns can be very painful and a number of different options may be used for pain management. These include simple analgesics (such as ibuprofen and acetaminophen) and opioids such as morphine. Benzodiazepines may be used in addition to analgesics to help with anxiety.[33] During the healing process, antihistamines, massage, or transcutaneous nerve stimulation may be used to aid with itching.[8] Antihistamines, however, are only effective for this purpose in 20% of people.[51] There is tentative evidence supporting the use of gabapentin[8] and its use may be reasonable in those who do not improve with antihistamines.[52]
Intravenous antibiotics are recommended before surgery for those with extensive burns (>60% TBSA).[53] As of 2008[update], guidelines do not recommend their general use due to concerns regarding antibiotic resistance[48] and the increased risk of fungal infections.[7] Tentative evidence, however, shows that they may improve survival rates in those with large and severe burns.[48] Erythropoietin has not been found to be effective to prevent or treat anemia in people with burns.[7] In burns caused by hydrofluoric acid, calcium gluconate is a specific antidote and may be used intravenously and/or topically.[22]
Wounds requiring surgical closure with skin grafts or flaps (typically anything more than a small full thickness burn) should be dealt with as early as possible.[54] Circumferential burns of the limbs or chest may need urgent surgical release of the skin, known as an escharotomy.[55] This is done to treat or prevent problems with distal circulation, or ventilation.[55] It is uncertain if it is useful for neck or digit burns.[55] Fasciotomies may be required for electrical burns.[55]
Honey has been used since ancient times to aid wound healing and may be beneficial in first- and second-degree burns.[56][57] The evidence for aloe vera is of poor quality.[58] While it might be beneficial in reducing pain,[11] and a review from 2007 found tentative evidence of improved healing times[59] a subsequent review from 2012 did not find improved healing over silver sulfadiazine.[58]
There is little evidence that vitamin E helps with keloids or scarring.[60] Butter is not recommended.[61] In low income countries, burns are treated up to one-third of the time with traditional medicine, which may include applications of eggs, mud, leaves or cow dung.[16] Surgical management is limited in some cases due to insufficient financial resources and availability.[16] There are a number of other methods that may be used in addition to medications to reduce procedural pain and anxiety including: virtual reality therapy, hypnosis, and behavioral approaches such as distraction techniques.[52]
| TBSA | Mortality |
|---|---|
| <10% | 0.6% |
| 10–20% | 2.9% |
| 20–30% | 8.6% |
| 30–40% | 16% |
| 40–50% | 25% |
| 50–60% | 37% |
| 60–70% | 43% |
| 70–80% | 57% |
| 80–90% | 73% |
| >90% | 85% |
| Inhalation | 23% |
The prognosis is worse in those with larger burns, those who are older, and those who are females.[10] The presence of a smoke inhalation injury, other significant injuries such as long bone fractures, and serious co-morbidities (e.g. heart disease, diabetes, psychiatric illness, and suicidal intent) also influence prognosis.[10] On average, of those admitted to United States burn centers, 4% die,[15] with the outcome for individuals dependent on the extent of the burn injury. For example, admittees with burn areas less than 10% TBSA had a mortality rate of less than 1%, while admittees with over 90% TBSA had a mortality rate of 85%.[62] In Afghanistan, people with more than 60% TBSA burns rarely survive.[15] The Baux score has historically been used to determine prognosis of major burns; however, with improved care, it is no longer very accurate.[7] The score is determined by adding the size of the burn (% TBSA) to the age of the person which used to more or less equal the risk of death.[7]
A number of complications may occur, with infections being the most common.[15] In order of frequency, potential complications include: pneumonia, cellulitis, urinary tract infections and respiratory failure.[15] Risk factors for infection include: burns of more than 30% TBSA, full-thickness burns, extremes of age (young or old), or burns involving the legs or perineum.[63] Pneumonia occurs particularly commonly in those with inhalation injuries.[7]
Anemia secondary to full thickness burns of greater than 10% TBSA is common.[5] Electrical burns may lead to compartment syndrome or rhabdomyolysis due to muscle breakdown.[7] Blood clotting in the veins of the legs is estimated to occur in 6 to 25% of people.[7] The hypermetabolic state that may persist for years after a major burn can result in a decrease in bone density and a loss of muscle mass.[34] Keloids may form subsequent to a burn, particularly in those who are young and dark skinned.[60] Following a burn, children may have significant psychological trauma and experience post-traumatic stress disorder.[64] Scarring may also result in a disturbance in body image.[64] In the developing world, significant burns may result in social isolation, extreme poverty and child abandonment.[3]
Disability-adjusted life years for fires per 100,000 inhabitants in 2004.[65]
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no data
< 50
50–100
100–150
150–200
200–250
250–300
|
300–350
350–400
400–450
450–500
500–600
> 600
|
As of 2004, 11 million burns required medical care worldwide and resulted in 300,000 deaths.[3] This makes it the 4th leading cause of injuries after motor vehicle collisions, falls, and violence.[3] About 90% of burns occur in the developing world.[3] This has been attributed partly to overcrowding and an unsafe cooking situation.[3] Overall, nearly 60% of fatal burns occur in Southeast Asia with a rate of 11.6 per 100,000.[15] The number of fatal burns has increased from 280,000 in 1990 to 338,000 in 2010.[66]
In the developed world, adult males have twice the mortality as females from burns. This is probably due to their higher risk occupations and greater risk-taking activities. In many countries in the developing world, however, females have twice the risk of males. This is often related to accidents in the kitchen or domestic violence.[3] In children, deaths from burns occur at more than ten times the rate in the developing than the developed world.[3] Overall, in children it is one of the top fifteen leading causes of death.[1] From the 1980s to 2004, many countries have seen both a decrease in the rates of fatal burns and in burns generally.[3]
An estimated 500,000 burn injuries receive medical treatment yearly in the United States.[33] They resulted in about 3,300 deaths in 2008.[1] Most burns (70%) and deaths from burns occur in males.[4][10] The highest incidence of fire burns occurs in those 18–35 years old, while the highest incidence of scalds occurs in children less than five years old and adults over 65.[10] Electrical burns result in about 1,000 deaths per year.[67] Lightning results in the death of about 60 people a year.[9] In Europe, intentional burns occur most commonly in middle aged men.[29]
In India, about 700,000 to 800,000 people per year sustain significant burns, though very few are looked after in specialist burn units.[68] The highest rates occur in women 16–35 years of age.[68] Part of this high rate is related to unsafe kitchens and loose-fitting clothing typical to India.[68] It is estimated that one-third of all burns in India are due to clothing catching fire from open flames.[69] Intentional burns are also a common cause and occur at high rates in young women, secondary to domestic violence and self-harm.[3][29]
Cave paintings from more than 3,500 years ago document burns and their management.[2] The earliest Egyptian records on treating burns describes dressings prepared with milk from mothers of baby boys,[70] and the 1500 BCE Edwin Smith Papyrus describes treatments using honey and the salve of resin.[2] Many other treatments have been used over the ages, including the use of tea leaves by the Chinese documented to 600 BCE, pig fat and vinegar by Hippocrates documented to 400 BCE, and wine and myrrh by Celsus documented to 100 CE.[2] French barber-surgeon Ambroise Paré was the first to describe different degrees of burns in the 1500s.[71] Guillaume Dupuytren expanded these degrees into six different severities in 1832.[2][72]
The first hospital to treat burns opened in 1843 in London, England and the development of modern burn care began in the late 1800s and early 1900s.[2][71] During World War I, Henry D. Dakin and Alexis Carrel developed standards for the cleaning and disinfecting of burns and wounds using sodium hypochlorite solutions, which significantly reduced mortality.[2] In the 1940s, the importance of early excision and skin grafting was acknowledged, and around the same time, fluid resuscitation and formulas to guide it were developed.[2] In the 1970s, researchers demonstrated the significance of the hypermetabolic state that follows large burns.[2]
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| リンク元 | 「火傷」 |
| 関連記事 | 「burning」「bur」「wound」「burn」 |