Burns 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 does not only affect the skin, it can have other effects on the tissue, organ and system networks such as smoke inhalation, as well as a psychological effect. It affects all gender although females have slightly higher rates of death from burn compared to males. It also affects all age group and it is the fifth most common cause of non-fatal childhood injuries.
Types of burns
- Electrical burn injury- Electrical burn injury is caused by heat that is generated when the electrical energy passes through the body causing deep tissue injury. The magnitude of the injury depends on the pathway of the current, the resistance of the current flow through the tissues, the strength, and the duration of the current flow. The different types of current causes various degrees of injury. For example, alternating current is more dangerous than the direct current and it is often associated with cardiac arrest, ventricular fibrillation, and tetanic muscle contractions.
- Thermal burn injury- Thermal burn injuries are caused by external heat sources (hot or cold) scalds (hot liquids), as a result of energy transfer. hot solid objects, steam and cold objects. The types of thermal burns are:
- Scalds- Scald burns injury results in about 70% of burns in children. They also often occur in elderly people. The common mechanisms are spilling hot drinks or liquids or being exposed to hot bathing water. Scalds tend to cause superficial to superficial partial burns.
- Flame- Flame burns are often associated with inhalation injury and trauma. It comprises 50% of adult burns and tends to be mostly deep dermal or full-thickness burn.
- Contact burn- These types of burns are commonly seen in people with epilepsy or those who misuse alcohol or drug or in elderly people after a loss of consciousness. Contact burns tend to be deep dermal or full-thickness burn. It occurs after contact with an extremely hot object or surface.
- Frostbite- It occurs when the skin is exposed to cold for a long time causing the freezing of the skin or other underlying tissue. It is due to direct cellular injury from the crystallization of water in tissue and indirect injury from ischemia.
3. Chemical burn injury- Chemical burn injury is caused by tissue contact with chemical agents such as strong acids, alkaline, or organic compounds. Chemical agents depending on the duration of exposure and the nature of the agent have different effects on the skin. For example, contact with acid causes coagulation necrosis of the tissue (whereby the architecture of the dead tissue can be preserved), while alkaline burns generate liquefaction necrosis (whereby the tissue is transformed into a liquid, viscous mass). Systemic absorption of some chemicals is life-threatening, and local damage can include the full thickness of skin and underlying tissues.
4. Radiation burn injury- Radiation burn is damage to the skin or other biological tissue and organs due to prolonged exposure to radiation. It is the least common burn injury and the most common type of radiation burn is the sunburn caused by prolonged exposure to Ultraviolet rays (UV). Other causes are associated with the use of ionizing radiation in industry, high exposure to radiotherapy e.g. X-ray, and nuclear energy. . Radiation burns are often associated with cancer due to the ability of ionizing radiation to interact with and damage DNA.
Classifications of burns
Burns can be classified according to their severity, depth, and size of the burn.
Classification according to depth are:
- Superficial thickness or First-degree burns- Superficial thickness burns are burns that affect the epidermis only and is characterized 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- 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 blister, are wet, waxy, or dry, and may appear ivory or pearly white.
- Full-thickness burns (third-degree) burns- It extends through the full dermis and often affects 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 and it is often blackened frequently leads to loss of the burned part.
Classification according to 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 burn patient. The body surface estimation is by assigning percentages to different body areas.
|Head and neck||9%|
|Lower extremity||18% each|
|Upper extremity||9% each|
Lund- Browder method- This method is used instead of the rule of nine methods 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 of 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.
Pathophysiology of burns
Burn injury depending on the severity of the injury can result in both local and debilitating systemic effects on all other organs and systems distant to the burn area.
- Zone of coagulation: This occurs at the point of maximum damage and this zone is characterized by irreversible tissue damage due to coagulation of the constituent proteins that occurs as a result of the insult.
- Zone of stasis or zone of ischemia: This zone lies adjacent to the zone of coagulation and it is subject to a moderate degree of damage associated with vascular leakage, elevated concentration of vasoconstrictors, and local inflammatory reactions resulting in compromised tissue perfusion. But the integrity of the tissue in this zone can be saved with proper wound care
- Zone of hyperemia: This is the outermost zone. It is characterized by the eased blood supply and inflammatory vasodilation. The tissue here will recover unless there is severe sepsis or prolong hypoperfusion.
In severe burn injury, >30% TBSA complex reaction occurs both from the burn area and in the area distant to the burn. Cytokines, chemokines and other inflammatory mediators are released in excess resulting in extensive inflammatory reactions within a few hours of injury. The initial response depending on the size of the burn injury is similar to the inflammation that is triggered after tissue destruction such as trauma or major surgery. Different factors contribute to the magnitude of the host response, they include: burn severity (percentage TBSA and burn depth), burn cause, inhalation injury, exposure to toxins, other traumatic injuries, and patient-related factors such as age, pre-existing chronic medical conditions, drug or alcohol intoxication, and timing of presentation to medical aid. This inflammatory response leads to rapid oedema formation which is caused by increased microvascular permeability, increased hydrostatic microvascular pressure, vasodilation, and increased extravascular osmotic activity. These reactions are due to the direct heat effect on the microvasculature and to the chemical mediators of inflammation. Vasodilation and increased venous permeability at the early stage of the injury are caused by the release of histamine. Also, prostaglandin is released by damage to the cell membranes which causes the release of oxygen-free radicals released from polymorphonuclear leucocytes which activate the enzymes catalyzing the hydrolysis of prostaglandin precursor. These hemodynamic changes lead to continuous loss of fluid from the blood circulation causing increased haematocrit levels and a rapid fall in plasma volume, leading to a decrease in cardiac output and hypoperfusion on the cellular level. Burn shock occurs if fluid loss is not adequately restored.
Besides, to burn shock, the burn injury can result in other types of injury which include inhalation injury. Inhalation injury is caused by heat or inhalation of smoke or chemical products of combustion leading to various degrees of damage. Usually, it is present in conjunction with the burn and can range from a minor injury to a severe injury. Inhalation injury can be divided into three types: systemic toxicity due to products of combustion (carbon monoxide (CO) and cyanide poisoning); upper airway thermal injury; and lower (bronchi and distal) airway chemical injury. Patients can sustain all of these in a closed- space fire. CO poisoning, more accurately categorized as a systemic intoxication, is easily diagnosed from the serum carboxyhaemoglobin level determined as part of the arterial blood gas measurement at hospital admission.
In addition to the effects above, severe burn injury has an effect on different organs and systems in the body. The effects include:
Effect on the cardiovascular system- The initial response to severe burn injury is characterized by hypovolemia and reduced venous return. This concomitantly leads to a decrease in cardiac output, increased heart rate, and peripheral resistance. In addition to the cardiac dysfunction, pulmonary resistance increase causing an increase in right and left-ventricular work-load.
Effect on the respiratory system- Following smoke inhalation, inflammatory mediators are released in the lungs leading to bronchoconstriction and adult respiratory distress syndrome.
Effect on the renal system- The renal system is affected following alterations in the cardiovascular system. Renal blood flow and glomerular filtration rate are reduced secondary to hypovolemia, diminished cardiac output, and the effects of angiotensin, vasopressin and aldosterone. These alterations are usually translated in the form of oliguria as an early sign of renal compromise. Failure to promptly and adequately manage these cases may lead to acute tubular necrosis, renal failure, and mortality.
Effect on the liver- There is substantial depletion of the hepatic proteins, alterations in serum levels of triglycerides and free fatty acids are highlighted, both of which are significantly increased secondary to a decrease in fat transporter proteins rendering the liver susceptible for fatty infiltration and hepatomegaly with resultant increased risk of sepsis and burn mortality.
Effects on gastrointestinal system/metabolism- The basal metabolic rate increases up to three times its original rate. This coupled with splanchnic hypoperfusion, necessitates early and aggressive enteral feeding to decrease catabolism and maintain gut integrity. It causes mucosal atrophy, reduced absorptive capacity, and increased surface permeability.
Effect on the Endocrine system-The stress hormones i.e. catecholamine, glucagon and cortisol among other hormones are actively involved at the onset of burn injury. These hormones display an exponential increase in their levels; sometimes reaching 10 fold their normal values. The significance of such an upsurge resides in its influence on the cardiovascular system and the resultant fluid shifts that follow these changes. The stress hormones are thereby considered as the initiators of the hypermetabolic-catabolic and proteolytic-response.
WHO in there reports made some recommendations for individuals, communities and public health officials on how to reduce burn risk.
- Enclose fires and limit the height of open flames in domestic environments.
- Promote safer cookstoves and less hazardous fuels, and educate regarding loose clothing.
- Apply safety regulations to housing designs and materials, and encourage home inspections.
- Improve the design of cookstoves, particularly about stability and prevention of access by children.
- Lower the temperature in hot water taps.
- Promote fire safety education and the use of smoke detectors, fire sprinklers, and fire-escape systems in homes.
- Promote the introduction of and compliance with industrial safety regulations, and the use of fire-retardant fabrics for children’s sleepwear.
- Avoid smoking in bed and encourage the use of child-resistant lighters.
- Promote legislation mandating the production of fire-safe cigarettes.
- Improve the treatment of epilepsy, particularly in developing countries.
- Encourage further development of burn-care systems, including the training of health-care providers in the appropriate triage and management of people with burns.
- Support the development and distribution of fire-retardant aprons to be used while cooking around an open flame or kerosene stove.
Burn injury has both physical, socio-economic, and psychological effects especially in cases of severe burn injury. Its effect is not only on the affected part of the body but it also has effects on the organs and systems of the body. It requires an early and prompt response to reduce the effect of the injury. Besides, it requires an interdisciplinary approach and management to prevent the adverse effect of the injury.
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