Introduction to Burns

Original Editor - Carin Hunter based on the course by [TUTOR LINK/ PhysioPlus ReLab]
Top Contributors - Carin Hunter, Jess Bell, Stacy Schiurring, Kim Jackson and Nikhil Benhur Abburi

What is a Burn?

A burn is an injury to the skin or other organic tissue primarily caused by exposure to heat or other causative agents (radiation, electricity, chemicals). According to WHO, it is a  global public health problem, accounting for an estimated 180,000 deaths annually. It is among the leading causes of disability in low and middle-income countries and almost two-thirds occur in the WHO African and South-East Asia regions. Burns do not only affect the skin, they can have other effects on the tissue, organ and system networks such as smoke inhalation, as well as psychological effects. Burns affect all genders although females have slightly higher rates of death from burns compared to males. They also affect all age groups and are the fifth most common cause of non-fatal childhood injuries.

Types of Burns

1. Thermal

Thermal burn injuries are caused by exposure to an external heat source or hot liquids. An external heat source can be a hot solid objects or even a cold object. Scalds are caused by wet substances, hot water, steam from hot water or cold water. The types of thermal burns are:

Flame Burns

Flame burns are caused by an exposure to an open fire. These are often associated with an inhalation injury and trauma. They tend to be mostly deep dermal or full-thickness burns. Flame burns are commonly found in adults but, they are also associated with abuse in children, domestic violence and certain rituals.

Contact Burns

Contact Burns are caused by contact with an extremely hot object or surface, commonly seem with stoves, heaters and irons. Contact burns tend to be deep dermal or full-thickness burns. They are commonly seen in people with epilepsy, those who misuse addictive substances or in elderly people after a loss of consciousness.

Frostbite or Ice Burns

Frostbite occurs when the skin is exposed to cold, typically any temperature below -0.55C (31F), for an extended period of time. This causes the water in the cells of the skin and underlying tissue to freeze and crystalise. An individual can suffer an injury from this crystallisation or indirectly from the tissue becoming ischemic. Frostbite can affect any part of your body, but the extremities, such as the hands, feet, ears, nose and lips, are most likely to be affected. If frostbite penetrates the deeper skin layers, impacting tissue and bone, it can cause permanent damage.

An Ice or Snow Burn is caused by ice or something very cold touching your skin for an extended period of time. Prolonged exposure to freezing temperatures, snow, or high-velocity winds can increase the chance of this type of burn. Ice burns are commonly caused by ice or cold packs being pressed directly against the skin when treating an injury or sore muscles.

Scalds

Scalds are caused by hot liquids. Commonly encountered liquids in this category are boiling water and cooking oil. Common mechanisms of injury is spilling of a hot drink or cooking oil or being exposed to hot bath water. Scalds tend to cause superficial to superficial partial burns. Scald burns result in about 70% of burns in children. They also often occur in elderly people.

2. Electrical burn, e.g. electrocution

An electrical burn is an injury caused by heat produced when an electrical current passes through a body. This can cause deep tissue injuries. The injury severity depends on many factors, the main ones being the pathway of the current, the resistance of the current in the tissues, and the strength and duration of the flow. Neither AC (Alternating Current) or DC (Direct Current) are more dangerous. But they can present with different symptoms. Patients that suffer from injuries with DC current, often cannot pull themselves away causing the duration of the injury to continue for longer. Electrical Burns are often associated with cardiac arrest, ventricular fibrillation, and tetanic muscle contractions.

For more information, please see AC and DC Electric Shock Effects Compared

3. Chemical Burns, e.g. Hydrofluoric Acid

Chemical burns or Caustic Burns are injuries cause by skin coming into direct contact with a chemical agent. These can be strong acids, alkaline, or organic compounds. Chemical compounds can have different effects on human tissue depending on the following:

• The strength or concentration of the chemical
• The site of contact (eye, skin, mucous membrane)
• Ingestion or inhalation
• Skin integrity
• Volume of substance
• Duration of exposure
• Chemical process
  • Acids can causes "coagulation necrosis" of the tissue.
  • Alkaline burns can cause "liquefaction necrosis".

4. Radiation burn

Radiation burn is damage due to prolonged exposure to radiation. The most common type of radiation burn is sunburn caused by prolonged exposure to Ultraviolet rays (UV). High exposure to radiotherapy can also cause erythema, known as radiation burns. These are often associated with cancer due to the ability of ionising radiation to interact with and damage DNA.

5. Inhalation Burns/Injury

Inhalation injury refers to pulmonary injury resulting from inhalation of smoke or chemical products of combustion. Inhalation injury results in direct cellular damage, alterations in regional blood circulation and perfusion, obstruction of the airways, and the release of pro-inflammatory cytokine and toxin release. Inhalation injuries also causes reduced functionality of mucociliary clearance and weakening of alveolar macrophages. This injury can be split into two categories: Heat Injury to the Upper Airway and Chemical Injury to the Lower Airways.

6. Friction Burn

A Friction Burn is an abrasion that occurs when the skin rubs against another surface. A Friction Burn is not a true burn, but because friction can generate heat, when an extreme case is seen, a patient will present with burns to the outer layer of the skin. Common causes are rope burn, rug burn, chafing or skinning.

Local Effect of Burns

This occurs immediately after the injury and the burn wound can be divided into three zones.

• Zone of Coagulation: This is the area central to the injury and is the area that suffers the greatest tissue damage.

• Zone of Stasis or Zone of Ischemia: This area is adjacent to the zone of coagulation and as the name suggests, it is a zone in which the there is slowing of circulating blood due to the damage. This zone can usually be saved with the correct wound care.

• Zone of Hyperemia: This zone is circumferential and is characterised by the eased blood supply and inflammatory vasodilation. This tissue has a good recovery rate, as long as there are no complications, such as severe sepsis or prolonged hypo-perfusion.

This video describes the pathophysiology of Burns

Degree or Classification of Burns

Burns can be classified according to their severity or depth, and size of the burn.

Classification by Depth

Superficial-Thickness or First-Degree Burns

- Superficial thickness burns are burns that affect the epidermis only and are characterised by redness, pain, dryness, and with no blisters. Mild sunburn is an example of a superficial thickness burn.

Partial-Thickness or Second-Degree Burns

- These burns involve the epidermis and a portion of the dermis. Partial-thickness burns are often broken down into two types, superficial partial-thickness burns and deep partial-thickness burns.

Superficial Partial-Thickness Burns

- Partial-thickness burns involve the epidermis and part for the dermis layer of the skin. Superficial partial-thickness burns extend through the epidermis down into the papillary, or superficial, a layer of the dermis. The injured site become erythematous because the dermal tissue has become inflamed. When pressure is applied to the reddened area. The area will blanch, but will demonstrate rapid capillary refill upon release of the pressure.

Deep Partial-Thickness Burns

- These burns extend deeper into the dermis and cause damage to the hair follicle and glandular tissue. They are painful to pressure, form blisters, are wet, waxy, or dry, and may appear ivory or pearly white.

Full-thickness or Third-Degree Burns

- These burns extend through the full dermis and often affect the underlying subcutaneous tissue. Skin appearance can vary from waxy white to leathery grey to charred and black. The skin is dry and inelastic and does not blanch to pressure, it is not typically painful due to the damage to the nerve endings. The dead and the denatured skin (eschar) are removed to aid healing and scarring is usually severe. Full-thickness burns cannot heal without surgery.

Subdermal or Fourth-Degree Burns

- These involve injury to the deeper tissues, such as muscle or bone. They are often blackened and it frequently leads to loss of the burned part.

Signs and Symptoms

The characteristics of a burn depend upon its depth. Superficial burns cause pain lasting two or three days, followed by peeling of the skin over the next few days. Individuals suffering from more severe burns may indicate discomfort or complain of feeling pressure rather than pain. Full-thickness burns may be entirely insensitive to light touch or puncture. While superficial burns are typically red in color, severe burns may be pink, white or black. Burns around the mouth or singed hair inside the nose may indicate that burns to the airways have occurred, but these findings are not definitive. More worrisome signs include: shortness of breath, hoarseness, and stridor or wheezing. Itchiness is common during the healing process, occurring in up to 90% of adults and nearly all children. Numbness or tingling may persist for a prolonged period of time after an electrical injury. Burns may also produce emotional and psychological distress.

Type	Layers Involved	Appearance	Texture	Sensation	Healing Time	Prognosis and Complications
Superficial or First-Degree	Epidermis	Red without blisters	Dry	Painful	5–10 days	Heals well. Repeated sunburns increase the risk of skin cancer later in life.
Superficial Partial Thickness or Second-Degree	Extends into superficial (papillary) dermis	Redness with clear blister. Blanches with pressure.	Moist	Very painful	2–3 weeks	Local infection (cellulitis) but no scarring typically
Deep Partial Thickness or Second-Degree	Extends into deep (reticular) dermis	Yellow or white. Less blanching. May be blistering.	Fairly dry	Pressure and discomfort	3–8 weeks	Scarring, contractures (may require excision and skin grafting)
Full Thickness or Third-Degree	Extends through entire dermis	Stiff and white/brown. No blanching.	Leathery	Painless	Prolonged (months) and unfinished/incomplete	Scarring, contractures, amputation (early excision recommended)
Fourth-Degree	Extends through entire skin, and into underlying fat, muscle and bone	Black; charred with eschar	Dry	Painless	Does not heal; Requires excision	Amputation, significant functional impairment and in some cases, death.

Classification by Size

Burn size is determined by one of the three techniques: The Rule of Nine, The Lund-Browder Method, The Palmar Surface.

The Rule of Nine

- This method is also known as the Wallace Rule of Nines because it is named after Dr Alexander Wallace the surgeon who first publish the method. The Rule of Nine is used to estimate the total body surface area (TBSA) involved in burn patients and also used to estimate fluid resuscitation required by a burns patient. The body surface estimation is by assigning percentages to different body areas.

Body Part	Percentage
Head and Neck	9%
Anterior Trunk	18%
Posterior Trunk	18%
Lower Extremity	18% each
Upper Extremity	9% each
Groin	1%

Lund-Browder Method

- This method is used instead of the rule of nine method for assessing the total surface area affected in children. Different percentages are used because the ratio of the combined surface area of the head and neck compared to the surface area of the limbs is typically larger in children than in adults.

Palmar Surface Method

- The palmar surface can be used to estimate relatively small burns or large burns. But for medium size burns, it is inaccurate. The surface area of a patient’s palm including the fingers is used to calculate the TBSA.