Burn

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Overview
A burn is an injury 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 nerve endings. 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.

Classification by degree
The most common system of classifying burns categorizes them as first-, second-, or third-degree. Sometimes this is extended to include a fourth or even up to a sixth degree, but most burns are first- to third-degree, with the higher-degree burns typically being used to classify burns post-mortem. The following are brief descriptions of these classes:
 * First-degree burns are usually limited to redness (erythema), a white plaque and minor pain at the site of injury. These burns only involve the epidermis.
 * 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 most of the epidermis is lost with damage to underlying ligaments, tendons and muscle. Burn victims will exhibit charring of the skin, and sometimes hard eschars will be present. An eschar is a scab that has separated from the unaffected part of the body. These types of burns are often considered painless, because nerve endings have been destroyed in the burned area. Hair follicles and sweat glands may also be lost due to complete destruction of the dermis. Third degree burns result in scarring and may be fatal if the affected area is significantly large. If extensive enough, it can increase the risk of infection, including bacterial, and can result in death.
 * Fourth-degree burns damage bone tissue and may result in a condition called compartment syndrome, which threatens both the life of the limb and the patient.
 * Fifth-degree burns are burns in which most of the hypodermis is lost, charring and exposing the muscle underneath. Sometimes, fifth-degree burns can be fatal.
 * Sixth-degree burns, the most severe form, are burn types in which almost all the muscle tissue in the area is destroyed, leaving almost nothing but charred bone. Often, sixth-degree burns are 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.

Table 2. Scald Time (Hot Water)

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 may be 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 (but not all) that can cause moderate to 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 generally caused by an exogenous electric shock, such as being struck by lightning or defibrillated or cardioverted without a conductive gel. 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 may be caused by protracted and overexposure 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 the more dangerous of the two. 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 a specific type of burning that is caused by hot fluids or gases. They most commonly occur in the home from exposure to high temperature tap water.

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 (see frostbite) is a kind of burn which arises when the skin is in contact with a low-temperature body.

They can be caused by prolonged contact with moderately cold bodies (snow and cold air for instance) or brief contact with very cold bodies such as dry ice, liquid helium, liquid nitrogen, or liquid discharged from an upside-down gas duster. In such a case, the heat transfers from the skin and organs to the external cold body.

The effects are very similar to that of a burn caused by extreme heat. The remedy is also the same. For a minor cold burn, it is advisable to keep the injured organ under a flow of water of comfortable temperature. This will allow heat to transfer slowly from the water to the organs.

Management
A local anesthetic is usually sufficient in managing pain of minor first-degree and second-degree burns. However, systemic anti-inflammatory drugs such as naproxen 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 throughly 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. 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.

Once the burning process has been stopped, the patient should be volume resuscitated according to the Parkland formula, since such injuries can disturb a person's osmotic balance. This formula dictates the amount of Lactated Ringer'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. 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.

Treatment of low-grade burns
A local anesthetic is usually sufficient in managing pain of smaller first-degree and second-degree burns. Lidocaine can be administered to the spot of injury and will generally negate most pain.

Pathological Findings
Images courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology