Types of burns

Burns are usually caused by heat (thermal burns), such as fire, steam, tar, or hot liquids. Burns caused by chemicals are similar to thermal burns, whereas burns caused by radiation , sunlight , and electricity differ significantly. Events associated with a burn, such as jumping from a burning building, being struck by debris, or being in a motor vehicle crash, may cause other injuries.

Thermal and chemical burns usually occur because heat or chemicals contact part of the body's surface, most often the skin.

Chemical burns
Burns can also occur when chemicals are spilled onto the body and generate a reaction that creates heat. Chemical burns may be classified by their pH or acidity.
Acids are those with pH less than 7 and include common household compounds like acetic acid, hydrochloric acid, or sulfuric acid.
Bases or alkali compounds have a pH greater than 7. Ammonia is a common alkali found in the home.

A variety of household products fits this description:
Bleach
Concrete mix
Drain or toilet bowl cleaners
Metal cleaners
Pool chlorinators

Pathophysiology

Agents that cause chemical burns are described by mechanism of injury. The chemical classification scheme includes such categories as desiccants, vesicants, oxidizing agents, protoplasmic poisons, acids, and alkali agents.

Acids act through coagulative necrosis, forming an eschar that limits the penetration of the acid. Strong alkali cause liquefactive necrosis, resulting in saponification of fats and denaturation of proteins, ultimately allowing deeper penetration of the chemical. Oxidizing agents also denature proteins and often cause cell damage via cytotoxic effects. Protoplasmic poisons, such as hydrofluoric acid (HF), can form salts with cellular proteins. Desiccants dehydrate cells through an exothermic reaction. Finally, vesicants are thought to produce physiologic reactions that cause the release of amines along with a variety of other damaging processes. Despite these categories, precise classification of chemical agents remains difficult because agents often cause injury by more than one mechanism.

Tissue damage from chemical burns depends on several factors.
The strength or concentration of the agent
The site of contact (eye, skin, mucous membrane)
Whether swallowed or inhaled
Whether or not skin is intact
With how much of the agent you came into contact
The duration of exposure
How the chemical works

Signs and symptoms of chemical burns include the following:
Redness, irritation, or burning at the site of contact
Pain or numbness at the site of contact
Formation of blisters or black dead skin at the contact site
Vision changes if the chemical gets into your eyes
Cough or shortness of breath

Self-Care at Home
Begin basic first aid. Immediately call 911 if you have a severe injury, any shortness of breath, chest pain, dizziness, or other symptoms throughout your body. If you are aiding an injured person with these symptoms, lay the person down and immediately call 911.
Remove yourself or the victim from the accident area.
Remove any contaminated clothing.
Wash the injured area to dilute or remove the substance, using large volumes of water. Wash for at least 20 minutes, taking care not to allow runoff to contact unaffected parts of your body. Gently brush away any solid materials, again avoiding unaffected body surfaces.
Especially wash away any chemical in your eye. Sometimes the best way to get large amounts of water to your eye is to step into the shower.
Remove contaminated clothing
Brush away any dry powders or particles
Rinse the area with large amounts of water.

Treatment
Before burns are treated, the burning agent must be stopped from inflicting further damage. For example, fires are extinguished. Clothing—especially any that is smoldering (such as melted synthetic shirts), covered with a hot substance (for example, tar), or soaked with chemicals—is immediately removed.

Hospitalization is sometimes necessary for optimal care of burns. For example, elevating a severely burned arm or leg above the level of the heart to prevent swelling is more easily accommodated in a hospital. In addition, burns that prevent people from carrying out essential daily functions, such as walking or eating, make hospitalization necessary. Severe burns, deep second- and third-degree burns, burns occurring in the very young or the very old, and burns involving the hands, feet, face, or genitals are usually best treated at burn centers. Burn centers are hospitals that are specially equipped and staffed to care for burn victims.



Smoke Inhalation
Many people who have been burned in fires have also inhaled smoke. Sometimes people inhale smoke without sustaining skin burns. Smoke inhalation often causes no serious, lasting effects. However, if the smoke contains certain poisonous chemicals, is unusually dense, or inhalation is prolonged, serious problems can develop.

Hot smoke sometimes burns the throat, resulting in swelling. As the swelling narrows this area, airflow into the lungs is obstructed. Breathing hot steam can burn the lungs as well as the throat, causing severe breathing problems.

Inhalation of chemicals released in the smoke, such as hydrogen chloride, phosgene, sulfur dioxide, and ammonia, can cause swelling and damage to the windpipe (trachea) and even the lungs. Eventually, the small airways leading to the lungs narrow, further obstructing airflow. Smoke can also contain chemicals that poison the body's cells, such as carbon monoxide (see Poisoning: Carbon Monoxide Poisoning) and cyanide.

Damage to the trachea or the lungs can cause shortness of breath, which can take up to 24 hours to develop. Obstruction of airflow due to swelling of the airways can produce difficulty breathing air in, wheezing, and shortness of breath. People may have soot in the mouth or nose, singed nasal hairs, or burns around the mouth. Lung damage may cause chest pain, coughing, and wheezing. If the oxygen supply is depleted due to smoke, people may pass out. High levels of carbon monoxide in the blood may cause confusion or disorientation or may even be fatal.

To assess the extent of injury due to smoke inhalation, doctors may pass a flexible viewing tube (bronchoscope) into the trachea. Doctors may assess lung damage with a chest x-ray or with a test that determines the level of oxygen in the blood.

People who have inhaled smoke are given oxygen through a face mask. If a tracheal burn is suspected, a breathing tube is inserted through the nose or mouth in case the trachea later swells and obstructs airflow. If people begin to wheeze, drugs that open small airways such as albuterol may be given, usually as a mist that is combined with oxygen and inhaled through a face mask. If lung damage causes shortness of breath that persists despite use of a face mask and albuterol, a ventilator may be necessary. Relieving the stress of breathing conserves people's energy and usually allows faster recovery.


Electrical burns

Electrical burns may cause serious injury that is not readily apparent. Often the entry and exit points for the electrical shock may not be easily found.

Electricity flows more easily through tissues in the body that are designed to deal with electricity. Nerves and muscles are "wired" for this task and often are damaged. If significant muscle damage occurs, muscle fibers and chemicals can be released into the bloodstream causing electrolyte disturbances and kidney failure.

An electrical injury occurs when a current passes through the body, interfering with the function of an internal organ or sometimes burning tissue.

Often the main symptom is a skin burn, but not all people have visible injuries.
Doctors check the person for abnormal heart rhythms, fractures, dislocations, and spinal cord or other injuries.
Abnormal heart rhythms are monitored, burns are treated, and, if the burn caused extensive internal damage, intravenous fluids are given.
Electrical injury may result from contact with faulty electrical appliances or machinery or inadvertent contact with household wiring or electrical power lines. Getting shocked from touching an electrical outlet in the home or by a small appliance is rarely serious, but accidental exposure to high voltage causes about 400 deaths each year in the United States. 

The severity of the injury ranges from minor to fatal and is determined by the following factors:
Intensity of the current
Type of current
Pathway of the current through the body
Duration of exposure to the current
Electrical resistance to the current

Symptoms
Often, the main symptom of an electrical injury is a skin burn (see Burns), although not all electrical injuries cause external damage. High-voltage injuries may cause massive internal burns. If muscle damage is extensive, a limb may swell so much that its arteries become compressed (compartment syndrome—see Fractures: Compartment Syndrome), cutting off blood supply to the limb. If a current travels close to the eyes, it may lead to cataracts. Cataracts can develop within days of the injury or years later. If large amounts of muscle are damaged (a disorder called rhabdomyolysis), a chemical substance, myoglobin, is released into the blood. The myoglobin can damage the kidneys.

Treatment
First the person must be separated from the current's source. The safest way to do so is to shut off the current—for example, by throwing a circuit breaker or switch or by disconnecting the device from an electrical outlet. No one should touch the person until the current has been shut off, particularly if high-voltage lines could be involved.

High-voltage and low-voltage lines are difficult to distinguish, especially outdoors. Shutting off current to high-voltage lines is done by the local power company. Many well-meaning rescuers have been injured by electricity when trying to free a person.

Once the person can be safely touched, the rescuer should check to see if the person is breathing and has a pulse. If the person is not breathing and has no pulse, cardiopulmonary resuscitation (CPR) should be started immediately (see First Aid: First-Aid Treatment). Emergency medical assistance should be called for any person who has more than a minor injury. Because the extent of an electrical burn may be deceptive, medical assistance should be sought if any doubt exists regarding severity.

People with rhabdomyolysis may receive large amounts of fluids intravenously. A tetanus shot is given if needed.

Skin burns are treated with burn cream (such as silver sulfadiazine, bacitracin,or sterile aloe vera) and sterile dressings. A person with only minor skin burns can usually be treated at home. If the injury is more severe, the person is admitted to the hospital, ideally a burn center. The person is kept in the hospital for 6 to 24 hours if any of the following exists:

The results of an ECG are abnormal
The person has lost consciousness
The person has symptoms of a heart problem (for example, chest pain, shortness of breath, awareness of heartbeats [palpitations])
The person has other severe injuries
The person is pregnant (in many, but not necessarily all, cases)
The person has a known heart problem (in many, but not necessarily all, cases)


UV light burn
Treatment: The key to minimizing the damaging effects of the sun is avoiding further sun exposure. Damage that is already done is difficult to reverse. Moisturizing creams and makeup help hide wrinkles. Chemical peels, alpha-hydroxy acids, tretinoin
creams, and laser skin resurfacing may improve the appearance of thin wrinkles and irregular pigmentation. Deep wrinkles and substantial skin damage, however, require significant treatment to be reversed.


Radiation injury
damage to tissues caused by exposure to ionizing radiation.
Large doses of ionizing radiation can cause acute illness by reducing the production of blood cells and damaging the gastrointestinal tract.
A very large dose of ionizing radiation can also damage the heart and blood vessels (cardiovascular system), brain, and skin.
Ionizing radiation can increase the risk of cancer, and damage to sperm and egg cells can increase the risk of genetic defects in offspring.
In general, ionizing radiation refers to high-energy electromagnetic waves (x-rays, gamma rays) and particles (alpha particles, beta particles, neutrons) that are capable of stripping electrons from atoms (ionization). Ionization changes the chemistry of affected atoms and any molecules containing those atoms. By changing molecules in the highly ordered environment of the cell, ionizing radiation can disrupt and damage cells.
onizing radiation is emitted by radioactive substances (radionuclides), such as uranium, radon, and plutonium. It is also produced by man-made devices, such as x-ray and radiation therapy machines.

Radio waves, such as from cell phones and AM and FM transmitters, and visible light also are forms of electromagnetic radiation. However, because of their lower energy, these forms of radiation are not ionizing, and thus public exposure levels from these common sources do not damage cells. In this discussion, “radiation” refers exclusively to ionizing radiation.

Contamination is contact with and retention of radioactive material, usually as a dust or liquid. External contamination is that on skin or clothing, from which some can fall or be rubbed off, contaminating other people and objects. Internal contamination is radioactive material deposited within the body, which it may enter by ingestion, inhalation, or through breaks in the skin. Once in the body, radioactive material may be transported to various sites, such as the bone marrow, where it continues to emit radiation, increasing the dose, until it is removed or emits all its energy (decays). Internal contamination is more difficult to remove than external contamination.

Irradiation is exposure to radiation but not to radioactive material, that is, no contamination is involved. A common example is diagnostic x-rays, such as for a broken bone. Radiation exposure can occur without direct contact between people and the source of radiation (such as radioactive material or an x-ray machine). When the source of the radiation is removed or turned off, irradiation ends. People who are irradiated but not contaminated are not radioactive, that is, they do not emit radiation, and their dose from that source of radiation does not continue to increase.

Effects of Radiation
The damaging effects of radiation depend on several factors:
The amount (dose)
How rapidly the dose is received
How much of the body is exposed
The sensitivity of particular tissues to radiation

Treatment
Physical injuries are treated before irradiation is treated because they are more immediately life-threatening. Irradiation has no emergency treatment, but doctors closely monitor people for the development of the various syndromes and treat the symptoms as they arise.

Contamination should be removed promptly to prevent the radioactive material from continuing to irradiate the person and to prevent the radioactive material from being taken up by the body. Contaminated wounds are treated before contaminated skin. Doctors decontaminate wounds by flushing them with a salt water solution and wiping them with a surgical sponge. After decontamination, wounds are covered to prevent recontamination as other sites are washed. Contaminated skin should be gently scrubbed with large amounts of soap and warm (not hot) water. Skin folds and nails need extra attention. Harsh chemicals, brushes, or scrubbing that may break the skin surface should be avoided. If hair cannot be decontaminated with soap and water, clipping it off with scissors is preferable to shaving. Shaving may cut the skin and allow contamination to enter the body. Skin and wound decontamination should continue until the Geiger-Muller counter shows that the radioactivity is gone or almost gone, until washing does not substantially reduce the amount of radioactivity measured, or until further cleaning risks damaging the skin. Burns should be gently rinsed but not scrubbed.

http://emedicine.medscape.com/article/1089490-overview
medline
merck.com
http://www.medicinenet.com/burns/page3.htm#tocf