Thermal injuries, commonly known as burns, occur when the skin or other tissues are damaged by heat. When excessive heat is transferred to the skin, it radiates outward from the point of contact and initiates local and, if severe enough, systemic responses from the body. The mechanism of injury depends on the heat source which can include flames, hot liquids, hot solid objects, and steam. The severity of the burn depends on the heat source temperature and duration of contact.
There are various types of thermal injuries:
Flash and flame burns: These can occur when someone is directly or indirectly exposed to a flame.
Scald burns: These occur when someone is exposed to a high-temperature liquid or steam. The exposure is generally from either a spill or immersion such as into a hot bathtub.
Grease burns: These occur when someone is exposed to high-temperature grease. Since grease has a higher viscosity than water and other thinner substances, it travels down the skin more slowly. Grease also does not evaporate resulting in a longer contact time with the skin. Therefore, these burns can be deeper than they initially appear.
Contact burns: These occur when someone comes into direct contact with a high-temperature object such as burners on a stove.
Inhalation injuries: Open flames in an enclosed space can cause facial and supraglottic burns. The products of combustion travel into the respiratory tract and cause mucosal irritation, bronchospasm, local or systemic inflammation, and capillary leak. This type of injury can be seen in house fires.
Resulting Injuries related to thermal injuries
Depth of Injury: The depth of thermal injury is directly related to the contact temperature, duration of exposure, and the thickness of the skin. Burns are typically classified into three degrees:
Local Response: The body’s response to a burn includes three zones similar to the rings of a bullseye.
Zone of Coagulation: This is the center of the bullseye and is the area of maximum damage where tissue is irreversibly destroyed.
Zone of Stasis: This is the next ring of the bullseye as you move out and surround the zone of coagulation. This area has decreased tissue perfusion but is potentially salvageable with proper treatment.
Zone of Hyperemia: The outermost ring of the bullseye and the one furthest from the point of contact. This area has more blood flow than the others and can usually recover unless there is a severe infection or prolonged hypoperfusion.
Systemic Response: Severe burns can trigger a systemic response, especially if they cover a large body surface area. This response can include:
Cardiovascular Changes: Increased capillary permeability leads to fluid loss and systemic hypotension.
Respiratory Changes: Inflammatory mediators can cause bronchoconstriction and, in severe cases, adult respiratory distress syndrome (ARDS).
Metabolic Changes: The basal metabolic rate can increase significantly, necessitating early and aggressive nutritional support.
Other Factors: Burns can also result from electrical discharge, friction, chemicals, and radiation. Each of these causes has its own unique mechanism of injury and effects on the body.
