Burn (injury)

This article describes a type of injury. For other meanings of the word, see burn.

In medicine, a burn is a type of injury to the skin caused by heat, electricity, chemicals, or radiation (an example of the latter is sunburn).

Classification

In classical medical literature, there were six degrees, the first three of which are still commonly used by the public:

First-degree burns are usually limited to redness (erythema), a white plaque and minor pain at the site of injury. These burns usually extend only into the epidermis.
Second-degree burns additionally fill with clear fluid, have 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.

Image:Burn 2nd degree 1.jpg|Evolution of a 2nd degree burn — One hour Image:Burn 2nd degree 2.jpg|Evolution of a 2nd degree burn — One day Image:Burn 2nd degree 3.jpg|Evolution of a 2nd degree burn — two days, the blister is appearing

Third-degree burns additionally have charring of the skin, and produce hard, leather-like eschars. An eschar is a scab that has separated from the unaffected part of the body. Frequently, there is also purple fluid. These types of burns are often painless (insensate) because nerve endings have been destroyed in the involved areas.

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, with decreased pain. Difficult to distinguish from full thickness
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)

Serious burns, especially if they cover large areas of the body, can cause death; any hint of burn injury to the lungs, for example through smoke inhalation, is a medical emergency.

Chemical burns are usually caused by chemical compounds, such as sodium hydroxide (lye), silver nitrate, and more serious compounds (such as sulfuric acid). Note that most chemicals (but not all) that can cause moderate to severe chemical burns are strong acids or bases. Nitric acid is possibly one of the worst burn-causing chemicals, as an oxidizer. Hydrofluoric acid can eat down to the bone and its burns are often not immediately evident. Most chemicals that can cause moderate to severe chemical burns are called caustic.

Electrical burns are generally symptoms of electric shock, being struck by lightning, being defibrillated or cardioverted without conductive gel, etc. The internal injuries sustained may be disproportionate to the size of the "burns" seen - as these are only the entry and exit wounds of the electrical current.

Survival and outcome (scars, contractures, complications) of severe burn injuries is remarkably improved if the patient is treated in a specialized burn center/unit rather than a hospital.

Scald

Scalding is a specific type of burning that is caused by hot fluids. Examples of common liquids that cause scalds are water and cooking oil. 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 can enter an orifice. However, deaths have occurred in more unusual circumstances, such as when people have accidentally broken a steam pipe.

Cold burn

A cold burn 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 for instance) or brief contact with very cold bodies such as dry ice, liquid helium or liquid nitrogen, which are used in the process of wart removal. In such a case, the heat transfers from the skin and organs to the external cold body (as opposed to most other situations where the body causing the burn is hotter, and transfers the heat into the skin and organs). The effects are very similar to a "regular" burn. The remedy is also the same as for any burn: for a small wound keep the injured organ under a flow of comfortably temperatured water; the heat will then transfer slowly from the water to the organs and help the wound. Further treatment or treatment of more extended wound also as usual.

Assessing burns

Burns are 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.

*Table 2*. Rule of nines for assessment of total body surface area affected by a burn
Anatomic structure	Surface area
Head	9%
Anterior Torso	18%
Posterior Torso	18%
Each Leg	18%
Each Arm	9%
Genitalia/perineum	1%

Management

The first step in managing a person with a burn is to stop the burning process. With dry powder burns, the powder should be brushed off first. With other burns, the affected area should be rinsed with a large amount of clean water to remove foreign bodies and help stop the burning process. Cold water should never be applied to any person with extensive burns, as it may severely compromise the burn victim's temperature status.

At this stage of management, it is also critical to assess airway status. If the patient was involved in a fire, then he or she has inhalation injury until proven otherwise, and should be managed accordingly.

Once the burning process has been stopped, and airway status is ensured, the patient should be volume resuscitated according to the Parkland formula. This formula dictates that the amount of Lactated Ringer's solution to deliver in the first twenty four hours after time of injury is:

Fluid = 4cc x %TBSA x weight in kg

%TBSA excludes any first degree burn

Half of this 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 urine output and central venous pressure. Inadequate fluid resuscitation causes renal failure and death.

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Classification

Scald

Cold burn

Assessing burns

Management

See also