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Burn (injury)
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A burn is a type of injury that may be caused by heat, cold, electricity, chemicals, light, radiation, or friction. Burns can be highly variable in terms of the tissue affected, the severity, and resultant complications. Muscle, bone, blood vessel, and epidermal tissue can all be damaged with subsequent pain due to profound injury to nerves. Depending on the location affected and the degree of severity, a burn victim may experience a wide number of potentially fatal complications including shock, infection, electrolyte imbalance and respiratory distress.
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Encyclopedia
A burn is a type of injury that may be caused by heat, cold, electricity, chemicals, light, radiation, or friction. Burns can be highly variable in terms of the tissue affected, the severity, and resultant complications. Muscle, bone, blood vessel, and epidermal tissue can all be damaged with subsequent pain due to profound injury to nerves. Depending on the location affected and the degree of severity, a burn victim may experience a wide number of potentially fatal complications including shock, infection, electrolyte imbalance and respiratory distress. Beyond physical complications, burns can also result in severe psychological and emotional distress due to scarring and deformity. It is generally accepted that a burn affecting more than one percent of the body surface, (approximately area of the casualty's palm) should be assessed by a medical practitioner.
Classification
The traditional system of classifying burns categorizes them as first-, second-, or third-degree. Most burns are first- to third-degree, with the higher-degree burns typically being used to classify burns postmortem. The following are brief descriptions of these classes:
This system is however being replaced by one reflecting the need for surgical intervention. The burn depths are described as either superficial, superficial partial-thickness, deep partial-thickness, or full-thickness.
By degree
- First-degree burns are usually limited to redness (erythema), a white plaque and minor pain at the site of injury. These burns involve only the epidermis. Sunburns can be included as first degree burns.
- Second-degree burns manifest as erythema with superficial blistering of the skin, and can involve more or less pain depending on the level of nerve involvement. Second-degree burns involve the superficial (papillary) dermis and may also involve the deep (reticular) dermis layer.* Third-degree burns occur when the epidermis is lost with damage to the subcutaneous tissue. Burn victims will exhibit charring and extreme damage of the epidermis, and sometimes hard eschar will be present. Third-degree burns result in scarring and victims will also exhibit the loss of hair shafts and keratin. These burns may require grafting.
- Fourth-degree burns damage muscle, tendon, and ligament tissue, thus result in charring and catastrophic damage of the hypodermis. In some instances the hypodermis tissue may be partially or completely burned away as well as this may result in a condition called compartment syndrome, which threatens both the life and the limb of the patient. Grafting is required if the burn does not prove to be fatal.
Other classifications
A newer classification of "Superficial Thickness", "Partial Thickness" (which is divided into superficial and deep categories) and "Full Thickness" relates more precisely to the epidermis, dermis and subcutaneous layers of skin and is used to guide treatment and predict outcome.
Table 1. A description of the traditional and current classifications of burns.
| Nomenclature | Traditional nomenclature | Depth | Clinical findings |
|---|
| Superficial thickness | First-degree | Epidermis involvement | Erythema, minor pain, lack of blisters | | Partial thickness — superficial | Second-degree | Superficial (papillary) dermis | Blisters, clear fluid, and pain | | Partial thickness — deep | Second-degree | Deep (reticular) dermis | Whiter appearance | | Full thickness | Third- or Fourth-degree | Dermis and underlying tissue and possibly fascia, bone, or muscle | Hard, leather-like eschar, purple fluid, no sensation (insensate) |
An even simpler, more accurate and more descriptive classification is epidermal, dermal and full thickness. Dermal injuries are subdivided into superficial, mid and deep.
Burns can also be assessed in terms of total body surface area (TBSA), which is the percentage affected by partial thickness or full thickness burns (superficial thickness burns are not counted). The rule of nines is used as a quick and useful way to estimate the affected TBSA.
Causes of burns
Burns are caused by a wide variety of substances and external sources such as exposure to chemicals, friction, electricity, radiation, and extreme temperatures, both hot and cold.
Most chemicals that cause severe chemical burns are strong acids or bases. Chemical burns are usually caused by caustic chemical compounds, such as sodium hydroxide, silver nitrate, and more serious compounds (such as sulfuric acid and Nitric acid). Hydrofluoric acid can cause damage down to the bone and its burns are sometimes not immediately evident.
Electrical burns are caused by an exogenous electric shock. Common causes of electrical burns include workplace injuries or being defibrillated or cardioverted without a conductive gel. Lightning is a rare cause of electrical burns. The internal injuries sustained may be disproportionate to the size of the burns seen, and the extent of the damage is not always obvious. Such injuries may lead to cardiac arrhythmias, cardiac arrest, and unexpected falls with resultant fractures.
Radiation burns are caused by protracted exposure to UV light (as from the sun), tanning booths, radiation therapy (as patients who are undergoing cancer therapy), sunlamps, and X-rays. By far the most common burn associated with radiation is sun exposure, specifically two wavelengths of light UVA, and UVB, the latter being more dangerous. Tanning booths also emit these wavelengths and may cause similar damage to the skin such as irritation, redness, swelling, and inflammation. More severe cases of sun burn result in what is known as sun poisoning.
Scalding
Scalding is caused by hot liquids or gases, most commonly occurring from exposure to high temperature tap water. A blister is a "bubble" in the skin filled with serous fluid as part of the body's reaction to the heat and nerve damage. Steam is a common gas that causes scalds. The injury is usually regional and usually does not cause death. More damage can be caused if hot liquids enter an orifice. However, deaths have occurred in more unusual circumstances, such as when people have accidentally broken a steam pipe. The demographics that are of the highest risk to suffering from scalding are young children, with their delicate skin, and the elderly over 65 years of age.
Cold burn
A cold burn (compare frostbite) is a kind of burn which arises when the skin is in contact with a low-temperature object. They can be caused by prolonged contact with moderately cold objects (snow and cold air for instance) or brief contact with very cold objects such as dry ice, liquid helium, liquid nitrogen, liquid discharged from an upside-down gas duster, or other refrigerants. In such a case, the heat transfers from the skin and organs to the external cold object.
Hot tar burn
Polyoxyethylene sorbitan in Neosporin ointment or sunflower oil are excellent dispersing agents that facilitate the removal of hot tar from burns.
Management
A local anesthetic is usually sufficient in managing pain of minor first-degree and second-degree burns; also Aloe vera sap can be used to heal the burn area. However, systemic anti-inflammatory drugs such as naproxen or ibuprofen may be effective in mitigating pain and swelling. Additionally, topical antibiotics such as Mycitracin are useful in preventing infection to the damaged area. Lidocaine can be administered to the spot of injury and will generally negate most of the pain. Regardless of the cause, the first step in managing a person with a burn is to stop the burning process at the source. For instance, with dry powder burns, the powder should be brushed off first. With other burns, such as those caused by exposure to chemicals, the affected area should be rinsed thoroughly with a large amount of clean water to remove the caustic agent and any foreign bodies. Cold water should not be applied to a person with extensive burns, however, as it may compromise the burn victim's temperature status.
If the patient was involved in a fire accident, then it must be assumed that he or she has sustained inhalation injury until proven otherwise, and treatment should be managed accordingly. At this stage of management, it is also critical to assess the airway status. Any hint of burn injury to the lungs (e.g. through smoke inhalation) is considered a medical emergency.
Once the burning process has been stopped, the patient should be volume resuscitated according to the Parkland formula (4ml lactated ringers x TBSA % burned x pt. weight kg.), since such injuries can disturb a person's osmotic balance. This formula dictates the amount of Lactated Ringer's solution (Hartmann's solution) to deliver in the first twenty four hours after time of injury. This formula excludes first and most second degree burns. Half of the fluid should be given in the first eight hours post injury and the rest in the subsequent sixteen hours. Inhalation injuries in conjunction with thermal burns initially require up to 40-50% more fluid. The formula is a guide only and infusions must be tailored to the urine output and central venous pressure. Inadequate fluid resuscitation causes renal failure and death.
Adequate pain management, including administration of opioid analgesics and sometimes other medication (e.g. ketamine, tranquilizers or general anesthetics), is important to alleviate the severe distress from the burns.
Hyperbaric oxygenation has not been shown to be a useful adjunct to traditional treatments.
To help ease the suffering of a burn victim, they may be placed in a special burn recovery bed which evenly distributes body weight and helps to prevent painful pressure points and bed sores. Survival and outcome of severe burn injuries is remarkably improved if the patient is treated in a specialized burn center/unit rather than a hospital. Serious burns, especially if they cover large areas of the body, can result in death.
Reactions and complications
Following a major burn injury heart rate and peripheral vascular resistance increase. This is due to the release of catecholamines from injured tissues, and the relative hypovolemia that occurs from fluid volume shifts. Initially cardiac output decreases. At approximately 24 hours after burn injuries (for patients receiving fluid resuscitation) cardiac output returns to normal, then increases to meet the hypermetabolic needs of the body.
Infection is a major complication of burns. Infection is linked to impaired resistance from disruption of the skin's mechanical integrity and generalized immune suppression. The skin barrier is replaced by eschar. This moist, protein rich avascular environment encourages microbial growth. Migration of immune cells is hampered, and there is a release of intermediaries that impede the immune response. Eschar also restricts distribution of systemically administered antibiotics because of its avascularity.
Risk factors of burn wound infection include:
- burn > 30% TBS
- full-thickness burn
- extremes in age (very young, very old)
- preexisting disease e.g. diabetes
- virulence and antibiotic resistance of colonizing organism
- failed skin graft
- improper initial burn wound care
- prolonged open burn wound
Burn wounds are prone to tetanus. A tetanus booster shot is required if individual has not been immunized within the last 5 years.
Circumferential burns of extremities may compromise circulation. Elevation of limb may help to prevent dependent edema. An Escharotomy may be required.
Acute Tubular Necrosis of the kidneys can be caused by myoglobin and hemoglobin released from damaged muscles and red blood cells. This is common in electrical burns or crush injuries where adequate fluid resuscitation has not been achieved.
See also
External links
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