Etiology: types of burn injuries
Most burn injuries happen at work or at home, particularly in the kitchen. The cause determines the type of burn injury and may vary depending on the age of the patient. Here you can explore the causes of different types of burn injuries: thermal, chemical and electrical.
Fire (flame burns)
A common cause of fire injury is clothes catching fire.
There is a risk of inhalation injury due to inhalation of smoke – the hot air may cause edema of the larynx, which may lead to laryngeal obstruction.
When fire occurs in a closed room, there is a risk of carbon monoxide intoxication due to inhaled toxins that can enter the bloodstream.
Fire (flash burns)
Flash burns are caused by exposure to a high temperature for a short period of time.
They mostly affect the hands and face.
Due to the short duration of exposure, flash burns seldom cause an inhalation injury.
Scalds are caused by hot liquid or steam.
They are the most common cause of burn injury in young children.
Burn wound depth depends on:
- The temperature, type and amount of liquid
- The duration of exposure
Hot oil and fat
Burns caused by fat are mainly the result of domestic accidents.
The temperature of boiling water is 100 degrees Celsius, whereas the processing temperature of cooking fat or oil is 190 degrees Celsius.
Although the heat capacity of fat is lower than water, burn depth may be as severe or even more severe.
A contact burn is caused by touching a hot, solid object.
The burn depth is dependent on the temperature of the agent, the duration of contact and the pressure exerted on the skin.
Young children and the elderly are more at risk of deeper contact burns.
Deep contact burns should raise suspicion of non-accidental injury.
Chemical burns differ from thermal injury, and they are less common. But chemical burns can cause deep burn wounds.
Chemical burns are caused by exposure to:
- Household chemical products – drain cleaners (Caustic soda), disinfectants (phenols), toilet bowl cleaners (sulfuric acid)
- Industrial chemical products – alkalis, acids, cement (lime)
- Products used in the military – phosphorus and vesicants
It is most important to take a history of the patient. The depth of the burn depends on the type of chemical, its concentration and the duration of exposure.
Different types of chemicals have different impacts on the skin:
- Acids produce coagulative necrosis
- Alkalis produce liquefactive necrosis
- Vesicants produce ischemic and anoxic necrosis
The impact on the skin continues as long as the agent is not completely removed, inactivated, or sufficiently diluted.
Electrical injury is a physiological reaction caused by electric current passing through the body.
Electricity transforms into heat as it flows through body tissue, causing tissue damage. Electrical burns can also cause organ damage – e.g. abnormal heart rhythm, muscle weakness, rhabdomyolysis and kidney dysfunction.
The depth of electrical burns depends on voltage, duration of exposure and pathway of the flow.
Injuries may occur with or without direct contact to the power source. A flash burn caused by a high-voltage injury is an example of electrical injury without contact to the power source, and results in a burn of varying degrees, depending on the amperage.
Electrical injuries are divided into three groups: low-voltage, high-voltage and lightning.
Low-voltage injury is caused by electricity below 1,000 volts (V) – either alternating current (AC), e.g. household electrical supply, or direct current (DC), e.g. car battery.
Domestic low voltage injury is caused by 220-230V AC. When a circuit breaker is installed, the power is switched off instantly when there is a short circuit, before any damage to the skin or heart. If a circuit breaker is not installed, the power will not be switched off. Because of the alternating current, muscle spasm may prolong the duration of contact.
At the entrance and exit sites, this may result in deep skin lesions and the patient may complain of muscle pain.
A flash burn commonly occurs when a person causes a short circuit. Direct contact with the source of electricity is not necessary for this burn. The severity of the injury depends on the distance from the source and the amperage.
High-voltage injury is caused by electricity above 1,000V; can result in different injuries.
Flash burns appear in body areas not covered by clothes as dermal and subdermal burns. Heat radiation caused by the electric arch may cause direct burns to the skin and may also ignite clothing, resulting in full thickness burns.
Wounds at the entrance and exit site are always full thickness. When an entrance wound is obvious during prior examination, other parts of the body must be examined for exit wounds. If contact with the earth was over a large surface, exit wounds may be absent.
In between these sites, mainly in the limbs, extensive soft tissue necrosis may be present underneath normal skin. This manifests itself in a swollen and tense limb and resembles a compartment syndrome of a crush lesion.
The patient complains of deep pain and tenderness. On investigation the limb is very tense and painful upon palpation, and signs of decreased circulation may appear. Soft tissue necrosis leads to the production of the breakdown products of myoglobin and hemoglobin. These substances can cause renal failure. ECG and full blood, including renal function tests, must take place.
Lightning is high in voltage and amperage over a very short time period. A person can be struck by lightning directly or through another object.
The most common type of radiation injury is sunburn caused by UV radiation. This type of injury can also be caused by ionizing radiation (e.g. gamma rays) or radio frequency energy.
Frostbite is a freezing injury, often affecting peripheral body parts. Although the pathophysiology of frostbite differs from burn injury, certain (surgical) principles overlap with the treatment of burn wounds.
The severity of the injury depends on the duration of exposure to environmental conditions (such as low temperature and wind), combined with risk factors such as vascular impairment.
Ischemia caused by freezing may result in tissue loss. This may require amputation of affected body parts in the later stages, causing loss of function.
Other long-term effects of freezing injury are cold sensitivity, sensory loss, hyperhidrosis and chronic pain.