A burn is a type of injury to flesh caused by heat, electricity, chemicals, light, radiation or friction. Most burns only affect the skin (epidermal tissueand dermis). Rarely, deeper tissues, such as muscle, bone, and blood vessels can also be injured.
Burns may be treated with first aid, in an out-of-hospital setting, or may require more specialised treatment such as those available at specialised burn centers.
Managing burns is important because they are common, painful and can result in disfiguring and disabling scarring, amputation of affected parts or death in severe cases. Complications such as shock, infection, multiple organ dysfunction syndrome, electrolyte imbalance and respiratory distress may occur.
The treatment of burns may include the removal of dead tissue (debridement), applying dressings to the wound, administering large volumes of intravenous fluids, administering antibiotics and skin grafting.
While large burns can be fatal, modern treatments developed in the last 60 years have significantly improved the prognosis of such burns, especially in children and young adults. In the United States, approximately 4 out of every 100 people with injuries from burns will succumb to their injuries. The majority of these fatalities occur either at the scene or enroute to hospital.
Burns can be classified by mechanism of injury, depth, extent and associated injuries and comorbidities.
Currently, burns are described according to the depth of injury to the dermis and are loosely classified into first, second, third and fourth degrees. This system was devised by the French barber-surgeon Ambroise Pare and remains in use today.
It is often difficult to accurately determine the depth of a burn. This is especially so in the case of second degree burns, which can continue to evolve over time. As such, a second-degree partial-thickness burn can progress to a third-degree burn over time even after initial treatment. Distinguishing between the superficial-thickness burn and the partial-thickness burn is important, as the former may heal spontaneously, whereas the latter often requires surgical excision and skin grafting.
The following tables describe degrees of burn injury under this system as well as provide pictorial examples.
In order to determine the need for referral to a specialised burn unit, the American Burn Association devised a classification system to aid in the decision-making process. 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 (TBSA) burnt, the involvement of specific anatomical zones, age of the person and associated injuries.
By surface area
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. First degree (erythema only, no blisters) burns are not included in this estimation. The rule of nines is used as a quick and useful way to estimate the affected TBSA. More accurate estimation can be made using Lund & Browder charts which take into account the different proportions of body parts in adults and children.
The size of a person's hand print (palm and fingers) is approximately 1% of their TBSA. The actual mean surface area is 0.8% so using 1% will slightly over estimate the size. Burns of 10% in children or 15% in adults (or greater) are potentially life threatening injuries (because of the risk of hypovolaemic shock) and should have formal fluid resuscitation and monitoring in a burns unit.
Burns are caused by a wide variety of substances and external sources such as exposure to chemicals, friction, electricity, radiation, and heat.
Most chemicals that cause chemical burns are strong acids or bases. Chemical burns can be caused by caustic chemical compounds such as sodium hydroxide or silver nitrate, and acids such as sulfuric acid. Hydrofluoric acid can cause damage down to the bone and its burns are sometimes not immediately evident.
Electrical burns are caused by either an electric shock or an uncontrolled short circuit. (A burn from a hot, electrified heating element is not considered an electrical burn.) Common occurrences of electrical burns include workplace injuries, or being defibrillated or cardioverted without a conductive gel. Lightning is also a rare cause of electrical burns.
Since normal physiology involves a vast number of applications of electrical forces, ranging from neuromuscular signaling to coordination of wound healing, biological systems are very vulnerable to application of supraphysiologic electric fields.
Some electrocutions produce no external burns at all, as very little current is required to cause fibrillation of the heart muscle. Therefore, even when the injury does not involve any visible tissue damage, electrical shock survivors may experience significant internal injury.
The internal injuries sustained may be disproportionate to the size of the burns seen (if any), 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 or dislocations.
The true incidence of electrical burn injury is unknown. In one study of 220 deaths due to electrical injury, 40% of those associated with low-voltage (<500 AC volts) injury demonstrated no skin burns or marks whatsoever. Most household electrical burns occur at 110 AC volts. This is sufficient to cause cardiac arrest and ventricular fibrillation but generates relatively low heat energy deposit into skin, thus producing few or no burn marks at all.
Radiation burns are caused by protracted exposure to UV light (as from the sun), tanning booths, radiation therapy (in people undergoing cancer therapy), sunlamps, radioactive fallout, 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 or "heatstroke". Microwave burns are caused by the thermal effects of microwave radiation.
Scalding (from the Latin word calidus, meaning hot) is caused by hot liquids (water or oil) or gases (steam), most commonly occurring from exposure to high temperature tap water in baths or showers or spilled hot drinks. A so called immersion scald is created when an extremity is held under the surface of hot water, and is a common form of burn seen in child abuse.
A blister is a "bubble" in the skin filled with serous fluid as part of the body's reaction to the heat and the subsequent inflammatory reaction. The blister "roof" is dead and the blister fluid contains toxic inflammatory mediators. Scald burns are more common in children, especially "spill scalds" from hot drinks and bath water scalds.
The list of treatments mentioned in various sources for Burns includes the following list. Always seek professional medical advice about any treatment or change in treatment plans.
Treatments of minor burns or minor scalds:
- Run under cold water for about 10 minutes.
- Do not use ice.
- Pat dry the skin after washing.
- Dressing or bandage over burn.
- Regular changes to burn dressings or bandages.
- Keep burn dressing clean and dry.
Treatments of more severe burns or scalds:
- Sterile dressings.
- Preventive antiseptics.
- Preventive antibiotics.
Treatments of very severe burns:
- Emergency treatment.
- Pain relief medications.
- Preventive antiseptics.
- Preventive antibiotics.
- Skin grafts.