Burns, Thermal

Introduction
Background

Burn injuries account for an estimated 700,000 annual ED visits per year. Of these, 45,000 require hospitalization. Approximately half of these patients are hospitalized at one of the 125 specialized burn treatment centers in the United States.

Most burns are not life threatening, but each burn causes a significant amount of pain for the patient and often some degree of psychological trauma. At temperatures greater than 120 º F, a child's skin is burned severely enough to require surgery in 3 seconds. Rapid evaluation by the emergency physician (EP) is essential to address pain management, provide initial wound care, evaluate appropriate disposition, mitigate the psychological impact of the burn, and identify intentional burns. Follow-up for even superficial thickness burns is imperative, particularly when involving the hands, feet, face, genital area, or other particularly sensitive areas.

To effectively evaluate, treat, and prevent potential future burns, understanding the different methods of categorizing burns is helpful. The general categories include life-threatening versus non–life-threatening, accidental versus intentional, recreational versus occupational, and domestic (home or residence) versus industrial.

Identifying the type of burn is essential because interventions must be appropriately tailored to the underlying cause. Type of burns include thermal burns, chemical burns, and radiation burns. Thermal burns can be further classified according to skin depth and percentage of total body area burned. Additional descriptions for thermal burns include contact, flame, heat, and scalding. Accurate documentation of the burn location (such as ophthalmic, hand, face, inhalation, soles, or perineum) and measurement of involved surface area are essential for follow-up and specialist referral/consultation.
Pathophysiology

The skin is the largest organ of the body. Although not very active metabolically, the skin serves multiple functions essential to the survival of the organism, which may be compromised by the presence of a burn, including the following:

* Thermal regulation and prevention of fluid loss by evaporation
* Hermetic barrier against infection
* Sensory receptors that provide information about environment

The skin is divided into 3 layers, as follows:

* Epidermis: This is the outermost layer of skin composed of cornified epithelial cells. Outer surface cells die and are sloughed off as newer cells divide at the stratum germinativum.
* Dermis: This is the middle layer of skin composed of primarily connective tissue. It contains capillaries that nourish the skin, nerve endings, and hair follicles.
* Hypodermis: This is a layer of adipose and connective tissue between the skin and underlying tissues.

The most common type of burns are thermal burns. Soft tissue is burned when it is exposed to temperatures above 115ºF (46°C). The extent of damage depends on surface temperature and contact duration. A thermal burn causes coagulation of soft tissue. As the marginally perfused areas become reperfused, it is thought that there is a release of vasoactive substances causing formation of reactive oxygen species, which leads to increases in capillary permeability. This causes fluid loss as well as increasing plasma viscosity with resultant microthrombi formation.1

This third spacing of fluid "seals" at 18-24 hours, which is why the guidelines for fluid resuscitation are based on a 24-hour time scale. After the initial 24 hours, the fluid requirements abruptly drop as the capillary permeability returns to normal. Underresuscitation in this initial 24-hour time period leads to significant morbidity from hypovolemia and shock.

Burns may cause a hypermetabolic state manifested by fever, increased metabolic rate, increased minute ventilation, increased cardiac output, decreased afterload, increased gluconeogenesis resistant to glucose infusion, and increased skeletal and visceral muscle catabolism. Patients need support in this state, which continues until wound closure is complete.1 To a large degree, how the individual responds to the increased energy demands determine recovery.
Frequency
United States

Nearly one million Americans seek ED treatment of burns each year. According to data provided by the American Burn Association, the incidence of burn injuries in the United States has declined from 2 million annual injuries estimated from 1957-1961.

According to 2007 data from the US Fire Administration, in 2006, 3,245 Americans lost their lives, and another 16,400 were injured as the result of fire. Notably, although the number of fires and deaths due to fires has decreased from 1997 to 2006, the direct dollar loss in millions has significantly increased from $8,525 to $11,307. Not included in these data are the deaths or the monetary value attributed to fires caused by the terrorist attacks of September 11, 2001. In 2002-2004, the United States had one of the highest fire death rates reported in the industrialized world at 12.4 deaths per million population, a slight decrease from 12.9 deaths per million population last reported in 2003.2 Most of these fatalities (79.5%) occurred in the home.

Slightly different findings were released by the World Fire Statistics in 2007.3 They reported that the fire-related death rate in the United States was 1.39 deaths per 100,000 (18.6 per million) in the years 2002-2004. For comparison, fire-related death rates per 100,000 were higher in Finland and Hungary at 2.08 and 2.10, respectively.

States with the highest death rates in 2004 were the District of Columbia (36.1 per million), Mississippi (32.1 per million), and Alabama (25.6 per million). The states with the lowest rates were Colorado (4.3 per million), Vermont (3.2 per million), and Wyoming (2 per million).2 Interestingly, in 2006, fire killed more Americans than all natural disasters combined.2

From 1990-2006, an estimated 2,054,563 patients aged 20 years or younger were treated in US EDs for burn-related injuries, with an average of 120,856 cases per year.4
International

The incidence of burn injuries varies from country to country, typically peaking during the country's holiday period.

In 2007, the World Fire Statistics Centre released fire-related death data by country (from lowest to highest number of deaths per 100,000 person) from 2002-2004.3 The countries with the lowest incidences include Singapore (0.08) and Switzerland (0.51). Those with the highest include Finland (2.08) and Hungary (2.10).3

In the United Kingdom, more than 47 fire-related injuries occur every day.

In Greece, the estimated annual incidence of childhood firework injuries treated in EDs is 7 injuries per 100,000 children per year. Seventy percent of injuries occur in children aged 10-14 years. Boys sustain self-inflicted accidental injuries; girls are typically injured as bystanders. A sharp peak of firework injuries occurs in the spring when the Greek Orthodox Easter is celebrated.5

Interesting data from Northern Ireland allows a comparison of burn incidence before and after the enactment of firework legislation. In the prelegislation series, the mean number of patients admitted annually was 0.38 per 100,000, whereas in the postlegislation series, the mean was 0.43 per 100,000. The authors concluded that legislation did not significantly affect the incidence of burns. Also in Northern Ireland, blast injuries to the hand account for more than 50% of injuries in this series.6
Mortality/Morbidity

Although fire-related deaths still rank fifth in the leading causes of unintentional injury-related deaths,7 the number of deaths from fires and burns has declined since the 1960s. Improvements in burn care (ie, quality burn centers, recognition, and effective management of burn shock) have reduced the number of deaths in the early postburn period. Improved wound management and antibiotics have decreased deaths from burn wound infection as well. The legislature has passed acts aimed at the prevention of injury due to fires. In 1971, the Flammable Fabrics Act was passed in an attempt to regulate the sale of flammable children’s clothing, especially that of sleepwear in infants, as it was noted to be a major cause of morbidity and mortality. Over time, this decreased the number of fire-related deaths and injuries in children.8

However, the greatest factors in the reduction of burn-related deaths is the use of smoke detectors and regulations on hot water heater temperature. In the United States, most people killed in house fires die from smoke inhalation rather than from burns (see Smoke Inhalation and Toxicity, Carbon Monoxide).

Race

Native American and black children are more than 2 times and 3 times as likely to die in a fire than white children, respectively.7 Black children and adolescents had the highest rates of burn and fire-related deaths. This is attributed to the decreased likelihood of minorities to engage in safe practices (fireplace guards, smoke alarm use, and adjusting water heater temperature).7
Age

Minor burns are more common in younger adults, often as a result of cooking or occupational exposures. Teenaged males are at increased risk of injury from fireworks; scald injuries are more common in young children. Most scald injuries in young children result from improper setting of domestic hot water heaters and spillage of cooking pots or beverages. Both types of injuries are easily prevented.

Most children aged 4 years and younger who are hospitalized for burn-related injuries suffer from scald burns (65%) or contact burns (20%). Most scald burns to children, especially small children aged 6 months to 2 years, are caused by hot foods or liquids spilled in the kitchen or other areas where food is prepared and served.

Water heater temperature must be set lower than 120°F. Within 3 seconds, a child's skin can be burned severely enough to require surgery when they are scalded with water temperature greater than 120°F.

The EP must consider intentional injury when burn patterns, such as absence of splash marks, stocking glove distribution, sharply defined wound margins, soles, palms, and pinpoint "cigarette ash" burns, are identified. Children aged 4 years and younger and children with disabilities are at the greatest risk of burn-related death and injury, especially scald and contact burns.

The leading cause of residential fire-related death and injury among children aged 9 years and younger is due to carelessness. Fires kill more than 600 children aged 14 years and younger each year and injure approximately 47,000 other children. Approximately 88,000 children aged 14 years and younger were treated at hospital EDs for burn-related injuries; 62,500 were thermal burns and 25,500 were scald burns. The most common causes of product-related thermal burn injuries among children aged 14 years and younger are hair curlers, curling irons, room heaters, ovens and ranges, irons, gasoline, and fireworks.

Elderly persons are also at increased risk not only for having a burn-related injury but for having increased morbidity due to their thinner skin and decreased healing abilities.
Clinical
History

The EP must consider the type of burn (thermal, chemical, radiation) and the location during early burn management. Once it has been determined that the burn is a thermal burn, the EP can add to the description: contact (with source name), scald (with fluid or gas type), heat, and flame. Systemic injury, duration, intentional versus accidental, and location of the burn must all be considered during the critical early burn period.

Other important points to determine include the patient's tetanus immunization status as well as the components of the history including past medical history, medications, and allergies.

Ascertain the history early because often the paramedics may be the only source of information about the event.

History should also include the following:

* Medical personnel must consider abuse as a cause of burns in all children. As many as 10% of abuse cases involve burns (see Pediatrics, Child Abuse).
* Components of the history that should raise suspicion of abuse include the
o Multiple/conflicting stories of how injury was sustained
o Injury attributed to a sibling
o Injury claimed to be unwitnessed
o Injury incompatible with developmental level of the child
o Presence of adult male who is not child's father (such as mother's boyfriend) living in household
* Characteristics of the burn that should raise suspicion of abuse include the following:
o Pattern burns that suggest contact with an object
o Cigarette burns
o Stocking, glove, or circumferential burns
o Burns to genitalia or perineum
* All health care personnel are obligated to contact appropriate law enforcement and protective services if they suspect the burn was intentional.
* Medical personnel must be aware that burns resulting from abuse or neglect may also be seen in the geriatric population.

Physical

* Burn depth is described as superficial, partial thickness, or full thickness (corresponding to first, second, or third degree). (See Causes for more information.)
* Superficial (first-degree) burns involve only the epidermis.
o Tissue blanches with pressure.
o Tissue is erythematous.
o Tissue damage is minimal.
o Edema may be present; generally blisters do not form.
o Sunburn is a classic example of this type of burn (see Sunburn for more details and management).
o These wounds are red, dry, painful, and generally heal in 3-6 days without scarring.9
* Partial-thickness burns (second-degree) are often further delineated into superficial and deep types.;
o Epidermis and portions of the dermis are involved.
o Blisters usually form either very quickly or within 24 hours.
o Superficial and deep partial-thickness can be difficult to differentiate at the bedside. The difference lies in the depth of penetrance into the dermis with the transition occurring at about half of dermal depth. Superficial partial-thickness burns usually blanch and do not result in scarring. Deep partial-thickness burns often do not blanch and do scar. The deeper the injury, the longer the healing time, which may vary from 7-21 days in the more superficial dermis burns to greater than 21 days in the deep dermis burns.
o Adnexal structures (eg, sweat glands, hair follicles) are often involved, but enough of these structures are preserved for function, and the epithelium lining them can proliferate and allow for regrowth of skin.
o If deep second-degree burns are not cared for properly, edema, which accompanies the injury, and decreased blood flow in the tissue can result in conversion to full-thickness burn.
o These wounds are red, wet, and painful (with decreasing pain, color, and moisture with increasing depth into the dermis).9
* Full-thickness (third-degree) burns extend completely through the skin to subcutaneous tissue. They may involve underlying structures including tendon, nerves, muscle, or bone (sometimes previously referred to as fourth-degree burn). Full-thickness and partial thickness burns are shown in the image below.
*

Partial- and full-thickness burns from a structur...
Partial- and full-thickness burns from a structure fire. Note facial involvement.

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Partial- and full-thickness burns from a structur...

Partial- and full-thickness burns from a structure fire. Note facial involvement.

o These burns are characterized by charring of skin or a translucent white color, with coagulated vessels visible below.
o The area is insensate, but the patient complains of pain, which is usually a result of surrounding second-degree burn.
o As all of the skin tissue and structures are destroyed, healing is very slow. Full-thickness burns are often associated with extensive scarring because epithelial cells from the skin appendages are not present to repopulate the area.
o These wounds vary from waxy white, to charred and black often with a leathery texture, they are dry and usually painless to touch. These wounds generally do not heal on their own.9
* Burn extent
o The more body surface area (BSA) involved in a burn, the greater the morbidity and mortality rates and the difficulty in management. Emergency medical services (EMS) personnel tend to overestimate the extent of the burn, whereas ED personnel tend to underestimate it.
o An individual's palmar surface classically represents 1% of the BSA, but, in actuality, it represents about 0.4%, whereas the entire hand represents about 0.8%.10,11 A simple method to estimate burn extent is to use the patient's palmar surface including fingers to measure the burned area. Burn extent is calculated only on individuals with partial-thickness or full-thickness burn.
o Another quick method is to use the Rule of Nines to estimate the extent of burn injury (as is shown in the image below).
o

Rule of nines for calculating burn area.
Rule of nines for calculating burn area.

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Rule of nines for calculating burn area.

Rule of nines for calculating burn area.
o The head represents a greater portion of body mass in children than it does in adults. Lund and Browder first described a method for compensating for the differences, and the Lund and Browder Chart is used to calculate BSA in children (as is shown in the image below).
o

Lund and Browder chart illustrating the method fo...
Lund and Browder chart illustrating the method for calculating the percentage of body surface area affected by burns in children.

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Lund and Browder chart illustrating the method fo...

Lund and Browder chart illustrating the method for calculating the percentage of body surface area affected by burns in children.
o If the chart is unavailable, estimate BSA by the Rule of Nines and adjust for age as follows:
+ In children younger than 1 year, the head and neck are 18% of BSA and each leg is 15% of BSA. The torso and arms represent the same percentages as in adults (10% and 16%, respectively).
+ For each year older than 1 year, add 0.5% to each leg and decrease percentage for the head by 1% until adult values are reached.
* On the basis of burn extent and depth, EPs can determine the severity of burn injury and whether the patient requires transfer to a burn center. The American Burn Association has developed criteria for burn center admission, as follows:
o Full-thickness (third-degree) burns over 5% BSA
o Partial-thickness (second-degree) burns over 10% BSA
o Any full-thickness or partial-thickness burn involving critical areas (eg, face, hands, feet, genitals, perineum, skin over any major joint), as these have significant risk for functional and cosmetic problems
o Circumferential burns of the thorax or extremities
o Significant chemical injury, electrical burns, lightning injury, coexisting major trauma, or presence of significant preexisting medical conditions
o Presence of inhalation injury
o Greater than 15% BSA in adults
o Greater than 10% BSA in children
o Hand and foot burns can lead to significant morbidity if not properly treated; therefore, most are treated with aggressive therapy. However, with careful follow-up, the patient may be monitored on an outpatient basis.

Causes

* Flame burns
o Contact with open flame causes direct injury to tissue.
o Flame may ignite clothing. Although natural fibers tend to burn, synthetic fibers may melt or ignite, adding a contact burn component to the injury.
o If the burn occurs in an enclosed area, the patient is also at risk for CO poisoning and cyanide poisoning as well as inhalational injury from the smoke and heat.
* Contact burns
o Contact burns result from direct contact with a hot object.
o Burn injury is confined to the point of contact.
o Examples are burns from cigarettes and tools (eg, soldering irons, cooking appliances, curling irons).
* Scalds
o Scalds result from contact with hot liquids (as is shown in the image below).
o

Child with burns from a scald. Hot soup was spill...
Child with burns from a scald. Hot soup was spilled when the child grabbed the handle of a pot. Note the full-thickness burn to left upper part of the chest. Edema of the lips and blisters on the face and nose indicate second-degree burns of the face.

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Child with burns from a scald. Hot soup was spill...

Child with burns from a scald. Hot soup was spilled when the child grabbed the handle of a pot. Note the full-thickness burn to left upper part of the chest. Edema of the lips and blisters on the face and nose indicate second-degree burns of the face.
o The more viscous the liquid and the longer the contact with the skin, the greater the damage.
o Accidental scalds often show a pattern of splashing, with burns separated by patches of uninjured skin.
o In contrast, intentional scalds often involve the entire extremity, appearing in a circumferential pattern with a line that marks the liquid surface.
* Steam burns
o Steam burns most often occur in industrial accidents or result from automobile radiator accidents.
o These burns produce extensive injury from the high heat-carrying capacity of steam and the dispersion of pressurized steam and liquid.
o Steam inhalation can actually cause thermal injury to the distal airways of the lung.
* Gas burns
o Inhalation of hot gas normally does not injure distal airways, as the heat-exchange capacity of the upper airway is excellent.
o In this situation, the upper airway is at risk for thermal injury and subsequent occlusion due to edema.
o Distal airway injury is more likely to be due to the direct effects of the products of combustion on the mucosa and alveoli.
* Electrical burns, including lightning12
o Electrical burns produce heat injury by passing through tissue.
o Most problems from these burns present in patients exposed to more than 1000V.
o Children can have significant injury after exposure to 200-1000V.
o Ignition of clothing may produce some flame burn, but most of the injury is deep in the skin (see Electrical Injuries).
o Cardiac injury is prominent, and patients must be monitored for 4-72 hours depending on the strength of the voltage and the age of the patient.
o The EP must consider visceral injuries, long bone and spine fractures, myoglobinuria, and compartment syndromes.
* Flash burns
o Flash burns are a subset of flame burns and are a result of rapid ignition of a flammable gas or liquid.
o The body parts involved are those exposed to the agent when it ignites.
o Areas covered by clothing are usually spared.
o The face may be involved, but if this type of injury takes place outside, then the risk for inhalation injury is low. A careful examination of the airway is indicated.
o A classic example of this type of injury occurs when a person pours gasoline on a trash or leaf fire to increase the flame and is burned by the subsequent fireball.
* Tar burns (see Emergency Department Care)
* Chemical burns12
o Alkaline substances and acid substances can burn the skin and can be associated with systemic toxicity.
o Alkaline burns produce liquefactive necrosis and are considered higher risk burns due to their likelihood to penetrate deeper.
o Acid burns are the result of coagulation necrosis, limiting the depth and penetration of the burn.
o The upper GI tract and oropharynx may also be at risk if the chemicals were ingested; therefore, the EP should be aware that the airway may occlude due to edema.
o Circumoral burns may be present if the agent was ingested.

http://emedicine.medscape.com/article/769193-overview