Burns

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Contents

Introduction

Sustaining a burn injury during one's lifetime is almost a universally shared experience. Such injuries are usually the result of minor household mishaps that occur most commonly in the kitchen and result in a small, intensely painful area of skin damage that settles spontaneously within a few days. More serious injuries with their devastating physical, emotional, social, functional and economic consequences are uncommon. The potential life-threatening nature of major burn injuries and the natural tendency for progressing deterioration in the burn wound underlie the importance of a clear understanding of the major aspects of burn injuries. Such knowledge forms the basis of rational management aimed at preventing complications, decreasing further tissue damage and securing early wound healing with minimisation of the functional and social consequences.

A burn injury most commonly results from the transfer of heat energy from a burning source to the skin. Human tissue cells are intolerant to temperature rises, and cellular damage in the form of protein coagulation commences when warming to 45.C occurs. Other agents such as chemicals, exposure to cold and external force producing friction may cause skin damage producing the clinical picture of a burn injury.

The severity of the injury is dependant on the amount of energy absorbed by the skin. The energy absorbed will be determined by the intensity of the burning or injurious agent, the length of exposure to the energy source and the degree of insulation or protection provided by clothing. The more energy absorbed by the skin the greater the degree of cellular disruption that will occur and the greater the depth to which the injury will extend. The pattern and severity of the injury can often be predicted by contemplating the circumstances of the injury. Exposure to a flash such as gas or petrol vapour explosion will produce rapid but transient heating, resulting in damage and probable death of surface cells only. A long exposure such as immersion in hot water will result in slower but greater heat absorption, producing more extensive and deeper tissue injury. The effects of the burning incident are not necessarily confined to the skin. Heat and smoke containing noxious chemicals may be inhaled, especially when a burn injury occurs in a confined space such as a house fire. The absorbed heat and smoke may affect the respiratory passages, leading to marked swelling and oedema that can cause respiratory obstruction. Inhaled smoke may irritate and damage the lung parenchyma, producing a chemical pneumonitis with impairment of gas exchange, leading to respiratory failure.

The anatomy of the skin

Skin consists of an outer layer, the epidermis, that provides a barrier to water loss and bacterial infection. This layer is derived from the constant division of the cells in the basal layer. This layer is thrown into folds, the rete pegs, that extend into the underlying dermal layer. As the basal cells divide, they push the outer cells further to the surface, during which cell death occurs. The outer layer of epidermal cells desiccate to form the stratum corneum or horny layer, which becomes very thick on the soles of the feet and palms of the hand. The epidermis is nourished, supported and strengthened by the underlying hypocellular layer known as the dermis. The dermis is rich in collagen fibres, producing its strength, and elastin, which maintains the normal contour and elasticity to the skin. The dermis is also rich in capillaries providing nutrients to the outer epidermis. The rete pegs, sweat glands and hair follicles invaginate into the underlying dermis. These structures provide a supply of epithelial cells deep within the skin, allowing spontaneous healing of wounds involving loss of the outer layers of the dermis (Burn thickness in relation to skin structure.).

Burn thickness in relation to skin structure.

Pathology

The severity of the injury and the consequences to the sufferer depends upon the depth to which the burn extends and the overall size or surface area of the burn injury. The depth of the injury will determine the local consequences of the injury and the size will influence the systemic consequences.

The depth of the burn may be described in a variety of ways, but broad categorisation into superficial burns, partial-thickness burns and full-thickness burns provides a simple and clinically useful model to describe burn injuries.

Pathology of superficial burns

Rapid but transient exposure to high temperatures such as flash injuries or prolonged exposure to temperatures just above tolerable limits will produce damage or death to the surface epithelial cells only. This damage will excite an underlying inflammatory response in the tissues deep to the injury producing pain, swelling and hyperaemia, the classical triad of the inflammatory response. The surface layers of cells may peel off, leaving the sensitive deeper layers of the epidermis exposed. As the basal layer remains intact in such injuries, the epidermis will completely regenerate to normal thickness with a new outer stratum corneum. This process will usually take 7–10 days. Such a burn is described as a superficial burn.

Pathology of partial-thickness burns

If the injury occurs to a greater depth, the outer epithelium and part of the underlying dermis will be damaged. The magnitude of the underlying inflammatory response will be greater, with capillary dilatation, loss of integrity of capillary walls, leading to excessive leakage of fluid from the intravascular to the interstitial space in the area of the burn wound. This fluid consists mainly of water and electrolytes such as sodium and potassium but will contain some protein. The consequences and the clinical picture will depend on how deeply the injury extends into the dermis. If cell death occurs close to the dermal-epidermal junction, the relatively thin outer layer of dead cells may be stripped off the underlying dermis by the fluid accumulating as a result of the inflammatory response. This produces surface blisters. Beneath such blisters is a dermal layer still rich in basal cells from the retained rete pegs of the epidermis. These epidermal cells can quickly multiply and migrate to reform a confluent layer that will gradually thicken to produce a new but slightly thinner and slightly more delicate epidermis. With blistered burns this healing process, if not hampered by infection, is usually well underway by 10–14 days. Such wounds are described as a superficial partial thickness of burns.

If the line of demarcation between dead and damaged cells lies deeper within the dermis, the overlying layer of cells may either separate at the time of burning, leaving a moist, weeping, sensitive layer of exposed damaged dermis, or may remain as a blanched, waxy layer that is too thick and rigid for the fluid beneath to form a blister. The inflammatory process excited by the burn will aid autolysis of the dead cells at the line of demarcation. If the deeper layers of the dermis remain viable, scattered epithelial cells may be found within the retained sweat glands and hair follicles. These cells can multiply, forming small colonies of epithelial cells that will migrate and eventually coalesce with surrounding colonies to produce a confluent layer. This process may be slow and healing and may not be complete even beyond 6 weeks post-burn. Spontaneous healing of deep partial-thickness burns occurs with significant wound contraction and scar formation, with a very thin and friable epidermal layer. These wounds are described as deep partial-thickness burns and, although spontaneous healing may occur, the cosmetic and functional result is often unsatisfactory and inferior to that achieved with surgical wound closure.

Pathology of full-thickness burns

If cell death extends deep to the dermis, all the skin layers are lost. The burnt tissue dries, forming a thick leathery covering called an eschar. If left, this eschar gradually separates, leaving an underlying granulating deep wound that will gradually contract in size. Epithelium at the edges of this burn wound will slowly migrate into the wound in an attempt to produce wound closure. This epithelial migration is slow and spontaneous healing is only ever achieved in small full-thickness burns. The result of spontaneous healing in full-thickness burns is gross scarring and contractures.

Systemic effects of burns

With a burn injury involving less than 10% of the body surface areas, the inflammatory response leads to fluid shifts that are compensated for by normal homeostatic mechanisms such as peripheral vasoconstriction. With a burn injury to greater than 10% of the body surface area, the fluid that shifts from the intravascular to the extravascular space begins to compromise the cardiac output and overall tissue perfusion. Large burns are associated with the systemic liberation of the inflammatory mediators such as cytokines, which trigger the systemic inflammatory response syndrome, leading to generalised capillary permeability and large fluid shifts. Untreated, this process is associated with the development of hypovolaemic shock, with decreased renal perfusion resulting in renal failure and eventually multi-organ failure and death.

Infection

With burn injuries resulting in the loss of the outer protective layers of the epidermis, rapid colonisation of the wound occurs, with bacteria and fungi derived initially from the host and later from the surrounding environment. These organisms can easily invade more deeply into the exposed dermis, producing local tissue destruction, which further complicates healing and deepens the damage. If large areas of burns are infected, organisms may spread systemically leading to septicaemia. Common pathological organisms that invade and interfere with the natural healing of the burn wounds are Staphylococcus aureus, Streptococcus viridans and Pseudomonas pyocyanea. Meticulous wound care is necessary to prevent burn wound infection. Topical antimicrobial agents have been the preferred means of reducing burn wound infection. Systemic antibiotics are only indicated for the treatment of established or invasive burn wound infection.

Assessment and management of the burned patient

Emergency examination and treatment

Rapid assessment and treatment of major burns may be life saving. The possibility of coexisting injuries must always be considered, especially with burns associated with road traffic accidents, blast injuries and electrocution. Injuries may also occur from jumping while escaping from the heat source. The principles of initial management consist of immediate first aid, followed by primary and secondary survey with institution of simultaneous resuscitation.

First aid

Stop the burning process by smouldering flames and removing clothing to cool the burn wound.

For extensive burned areas cool water (ideal temperature 15.C) should be applied to cool the skin to normal temperatures. The patient should then be wrapped in loose dry material to prevent systemic cooling, which may lead to severe and at times fatal hypothermia. For small superficial burns, cooling will have a major analgesic effect and should be continued until the stinging sensation begins to abate.

Primary survey

The primary survey identifies and addresses immediate life-threatening conditions and consists of:

  • (A) Airways maintenance with cervical spine control
  • (B) Breathing and ventilation
  • (C) Circulation with haemorrhage control
  • (D) Disability and neurological status
  • (E) Exposure and environmental control

(A) Airways maintenance with cervical spine control

Check that the airway is clear of foreign materials and, if indicated, such as in the unconscious patient, open the airway by lifting the chin or thrusting the jaw forward using pressure behind the angles of the mandible. Never hyper-flex or hyper-extend the neck during these manoeuvres as there may be an associated unstable cervical spine injury. An oropharyngeal or nasopharyngeal airway may provide a temporary airway in unconscious patients, whilst a normal speaking voice indicates a clear airway, but deterioration may occur with time if heat has been inhaled.

(B) Breathing and ventilation

Burned patients may not be ventilating adequately due to a depressed conscious state secondary to cerebral injury or hypoxia associated with the burn. Inhalation of heat and smoke, which occurs commonly in house fires, may lead to inflammation and obstruction of the airways, impairing ventilation. Smoke and chemical irritation may also irritate the lungs, leading to impaired gaseous exchange.

To assess the adequacy of breathing and ventilation, fully expose the chest and check chest expansion. If this appears adequate, supplemental oxygen should be supplied using a face mask. If there were signs of respiratory obstruction or inadequate ventilation, initial ventilation via a bag and mask should be instituted while preparing for endotracheal intubation and assisted ventilation. If there is a clinical risk of the development of airway oedema or signs of respiratory obstruction early endotracheal intubation should be performed. Delay in intubation may see the very development of gross pharyngeal oedema necessitating an emergency tracheostomy or cricothyroidotomy to secure airway.

(C) Circulation with haemorrhage control

Check the state of the circulatory system.

  • Pulse and blood pressure assessment. If pulse is weak or blood pressure is low, immediate fluid resuscitation should be commenced.
  • Capillary refill test. Normal return should occur within 2 seconds.
  • Stop any external bleeding by applying direct pressure.

(D) Disability and neurological status

Establish and record the level of consciousness, which may be affected by direct cerebral injury or the result of hypoxia secondary to respiratory complications. A simple method of describing the disability is:

  • A - alert
  • V - response to verbal stimuli
  • P - response to painful stimuli
  • U - unresponsive.

(E) Exposure with environmental control

Remove all clothing to allow a rapid appraisal of the extent of the injury and keep the patient warm.

Secondary survey

Having stabilised any immediate life-threatening situations, a comprehensive assessment is undertaken.

History

All sources of information should be assessed including, most importantly, the information from ambulance officers or paramedics involved in the evacuation and transport of the patient (Key questions in taking the history of a burns patient).

Additional salient points of the history include:

  • A - allergies
  • M - medication
  • P - past illnesses
  • L - last meal
  • E - events/environment related to injury such as duration of exposure to heat, nature of the burning agent, first-aid measures applied and type of clothing worn.

Examination

A comprehensive head-to-toe examination is necessary to fully assess the extent of the burn injury and to detect any associated injuries.

Head and neck

Assess general signs of injury. Check for corneal burns. Look for indications of possible inhalation injury, such as burns or blistering of the nose and mouth, singeing of nasal hairs, soot in the mouth or pharynx and blisters or oedema of the tongue. Carefully check for signs of cervical spine injury.

Chest

Examine the whole chest, assessing the burn injury and whether it is compromising respiration. Look for evidence of rib fractures or flail chest. Listen for breath sounds and signs that might indicate inhalation injury to the lower airways.

Abdomen

Check for signs of associated intra-abdominal injuries if burns are associated with trauma. Assess if abdominal burns are restricting respiration.

Perineum

Check for perineal burns and other injuries.

Limbs

Assess for signs of soft tissue or bony injury. Assess the burns to determine if they are full-thickness and circumferential. Such burns may lead to constriction due to skin shrinkage during the burning process. With the subsequent development of oedema following the burns, this constriction may impair the venous return from the limb, leading to further swelling and eventual cessation of arterial inflow, producing tissue ischaemia and necrosis. Impaired limb perfusion leads to pain and paresthesia, progressing to numbness, pulselessness and paralysis. When venous return from an extremity is obstructed, an escharotomy or splitting of the burned tissue must be performed rapidly to restore adequate circulation.

Assessment of the burn

As previously described, the severity of the burn injury is determined by the extent and the depth of the burn injury.

Assessment of the extent of the burn

The burn extent is described as the percentage of total body surface area (TBSA) affected. In adults this can be roughly calculated by applying the ‘rule of nines’ (Rule of nines.). Each arm equals 9% body surface area, the head equals 9%, the anterior and posterior trunk equals 18% each, and each leg equals 18%. This is a simple and broadly accurate assessment tool. Estimation of small irregular burn areas may be performed using the size of the palm, which is approximately 1% of body surface area, as a measure. The use of Lund & Browder body charts is to be encouraged as they provide a permanent record of the extent of the burn injury and are more accurate as the accompanying tables taking into account the differing percentages for the limbs, trunk and head according to age.

Rule of nines.

Assessment of the depth of the burn

There is currently no accurate or readily available investigative tool for the assessment of burn wound depth and we must rely on the clinical characteristics. The depth, as previously described, can be broadly classified as superficial, partial-thickness or full-thickness.

Clinical features of superficial burns

Burns associated with death or damage to the outer layer of the epidermis, such as those resulting from sunburn or minor scalds, can be identified clinically by:

  • erythema that blanches on pressure
  • sensitivity to touch
  • absence of blisters.

Clinical features of partial-thickness burns

Burns involving the outer layer of the dermis are characterised by:

  • blisters suggesting superficial dermal involvement only
  • a weeping moist surface suggesting deeper dermal loss
  • some capillary return apparent in superficial partialthickness burns but absent in deeper dermal burns
  • sensation present and decreases the deeper the burn extends into the dermis
  • the colour may vary from pale pink to blotchy red
  • fresh bleeding when pricked with a needle.

Depth of full-thickness burns

Complete death of both epidermis and dermis is characterised by:

  • a white waxy to a charred colour
  • a firm to hard leathery texture (eschar)
  • loss of sensation to pin prick
  • absence of bleeding when pricked with needle.

Definitive management of the burn patient

Having fully assessed the magnitude of the clinical problem, a management plan is formulated that involves fluid resuscitation, pain management and treatment of the burn wounds.

Fluid resuscitation

Burns in adults involving greater than 10–15% TBSA and greater than 10% TBSA in children require fluid resuscitation to avoid the complications of systemic hypovolaemia.

There are a number of resuscitation formulas that have been developed to act as a guide to the volume of fluid that will be required to maintain adequate cardiac output during the early post-burn phase (first 48 hours). No resuscitation formula has been shown conclusively to have a survival advantage. The most commonly used formula is:

Adults: 3–4 mL Hartmans solution/kg bodyweight/% burn.

Children: As above plus maintenance fluids according to bodyweight using 4% glucose in one-quarter or one-fifth normal saline.

The volume commences from the time of the burn injury.

Half the calculated volume is given in the first 8 hours and the remaining half in the subsequent 16 hours. Fluid should be administered through large peripheral cannulae, preferably inserted through non-burnt tissue. Central venous access is helpful in large burns.

Monitoring adequacy of fluid resuscitation

The actual volume of fluid needed to adequately resuscitate a burn may vary considerably from the calculated volume due to the inaccuracies of burn wound assessment and the possibility of injuries such as inhalation, which will lead to a greater generalised inflammatory response. Formulas are general guides or starting points for resuscitation, which must be modified according to the clinical response. The easiest and most reliable method of assessing adequacy of fluid resuscitation is by monitoring urine output. Thus, for burns greater than 15% a urinary catheter should be inserted and urine flow of 0.5–1 mL/kg per hour for adults and of 1.0–2 mL/kg per hour for children (<30 kg) aimed for. Urine volumes greater than these levels should be avoided, as excessive resuscitation will lead to unnecessary tissue oedema and the possibility of pulmonary oedema. Red or brown discolouration of the urine indicates the presence of haemoglobin or myoglobin, suggesting muscle injury. This is commonly seen following electrocution or in the presence of a compartment syndrome. These haemochromogens, if concentrated, may become deposited in the proximal renal tubules, leading to acute renal failure. In the presence of haemochromogens, the urinary output should be maintained at a higher level, aiming for 1–2 mL/kg in adults until the urine clears. Occasionally mannitol or frusemide may be judiciously added to maintain an adequate urine flow.

Other forms of cardiovascular monitoring, such as central venous pressure or cardiac output studies, are usually only indicated for patients with premorbid cardiac disease or coexistent injuries causing blood loss.

Pain control

As in all major trauma pain, control is best achieved initially by incremental doses of intravenous narcotics, following which a continuous infusion or patientcontrolled analgesia is appropriate.

Treatment of the burn wounds

The management of the burn wound is determined by the clinical assessment of the burn depth and an understanding of the pathophysiology of the burn injury.

Treatment of superficial burns

Burns not associated with significant blistering are not prone to infection and will settle rapidly if care and protection are provided. Occlusive non-adherent dressings are applied to the wound. Elevating burned limbs will minimise oedema formation. Such wounds should resolve in 7–10 days.

Treatment of partial-thickness wounds

Blistering burns and those with intact sensation should heal spontaneously in 10–14 days, providing infection does not intervene. The introduction of effective topical antiseptic agents has been one of the major breakthroughs in the management of burn wounds. While no agent exists that will effectively destroy all bacteria and fungi, silversulphadiazine, a loose chemical combination of 1% silver nitrate with the organic compound sulphonamide sulphadiazine, does cover almost the entire spectrum. This cooling, soothing cream has minimal chances of contact sensitivity or systemic toxicity and provides a highly effective surface antibacterial agent, and should be applied to the burn wound immediately and dressings changed daily. Newer biosynthetic dressings that can adhere and seal cleaned superficial burn wounds have been shown to reduce pain and accelerate spontaneous healing. Their current high costs preclude routine use for superficial burn wounds.

Treatment of deep dermal and full-thickness burns

Burns extending deeply into the dermis may slowly heal spontaneously. Such healing is associated with significant scarring and deformity and a better cosmetic result can be achieved with surgical excision and grafting. Full-thickness burns clearly require excision and grafting to achieve wound healing.

Such surgery is ideally performed as soon as practicable to minimise the risk of infection and hasten the patient's full recovery. The surgical techniques involve removal of the burned tissue down to a living vascularised layer and the application of split-thickness skin harvested from a non-burned area of the body. For partial-thickness burns, the technique of tangential excision is used, where thin layers of the burn are shaved off until a freely bleeding surface is achieved. For deep and full-thickness burns, the outer burned layer is peeled off in a single sheet usually down to the underlying investing layer of fascia. This is known as fascial excision.

Donor skin can be harvested from most sites of the body. The thighs are preferred, but with large extensive burns all unburned areas except the face may need to be used. The donor skin must contain basal epithelial cells to produce a new epidermal layer and thus skin is harvested down to the level of the rete pegs. The donor sites heal by rapid migration of the remaining keratinocytes and such donor sites may be reharvested when healing is complete. This may be in as little as 7–10 days, depending upon the thickness of the skin taken and the texture of the donor sites. To prevent blood and fluid accumulating beneath the grafted skin, which will prevent the graft from becoming vascularised, the donor skin is usually passed through a meshing machine that produces multiple slits in the graft. Depending on the length of the slits, the skin may be expanded, allowing a larger area to be covered. This technique is useful in large burns where donor sites are limited. Such widely meshed skin relies on epithelial migration to fill the gaps in the mesh.

Plastic surgery

With appropriate wound management, as detailed above, the majority of patients achieve a very satisfactory functional and cosmetic result with their primary wound healing. Severely burned patients may have damage to underlying tendons, especially on the dorsum of the hand, around the elbow or the foot, for which split-thickness grafting techniques are not appropriate. In these circumstances vascularised skin flaps may be indicated. Reconstructive surgical techniques are also occasionally needed to correct contractures and deformities, particularly to the anterior neck and the axillary folds. Minimisation of such contractures and deformities is achieved by early wound closure and the physiotherapy and occupational therapy staff using active stretching and appropriate splinting techniques.

Nursing care of the patient

The nursing care of the burned patient is demanding both on patient and nurse. It requires a great deal of understanding and compassion from the latter and taxes the fortitude of the former, who has to put up with repeated and often painful dressing. The day-to-day care of the patient depends on good general nursing and good techniques with dressings. There is a vast array of differing techniques used for dressing the burned wounds. The basic principles to be observed are:

  • keep the wound clean and protected with the appropriate antibacterial bandage or occlusive dressing
  • facilitate the maximum mobility and joint function wherever possible
  • minimise pain and discomfort by a combination of gentle handling and appropriate analgesics.

The techniques of continuous narcotic infusion and patient-controlled anagelsia have greatly facilitated patient comfort and wound care.

Nutrition

Energy expenditure of the extensively burned patient is high and may be several times that of the normal basal level. A rapid drop in the patient's serum proteins and significant weight loss, especially involving loss of skeletal muscle mass, may occur in major burns. Nutritional support is vital for patient survival in the setting of major burns. For moderate burns the use of food supplements and fortified drinks may be adequate. For major burns, for example those involving more than 40% TBSA, patients are usually unable to meet their metabolic demands using diet alone, and continuous nasoenteral feeding is required. This is best achieved via a nasojejunal tube, which should be placed as soon as possible, and feeding commenced early. It is possible to feed the patient enterally in the presence of gastric stasis with an appropriately placed enteral feeding tube. Parenteral nutrition is uncommonly required unless there are associated abdominal problems.

Electrical burns

Electrical injury is uncommon. Carelessness is often a factor in its occurrence. Commonly, the so-called electrical injury is the result from the discharge of electrical energy causing a fire and is thus a burn and not due to electrocution. However, if the victim does connect with an electrical circuit, death can occur due to cardiac arrhythmia or respiratory paralysis, although this is relatively unusual. Electrocution produces an entry and exit wound with variable damage to the intervening conducting tissues. If deep tissue damage is suspected, both the entry and exit points in the areas in between should be explored. Extensive limb fasciotomies and muscle debridement may be required if significant current flows through soft tissues, producing swelling and muscle necrosis. The risk of cardiac damage, especially in injuries involving conduction of current through the left arm and exiting on the right side of the body, should be remembered. Cardiac monitoring is essential if there is a history or existing evidence of a change in cardiac rhythm or elevation of cardiac enzyme. In the absence of any evidence of initial cardiac involvement, prolonged monitoring is not required. With the appropriate management of arrhythmia, recovery from a cardiac injury after electrocution is generally complete.

Chemical burns

Strong acids and alkalis used for industrial purposes are the most frequent cause of chemical injuries resulting in a burn. Immediate dowsing in water is the appropriate first aid prior to transfer to hospital. Hydrofluoric acid used in glass etching is a particularly dangerous acid as it deeply penetrates the tissues and is not quickly neutralised. Medical attention must be sought immediately. Calcium gluconate gel or 10% of calcium gluconate injected locally must be used to neutralise the effects by binding with the free fluoride radicals. Sometimes immediate surgery to excise the already damaged tissue and to prevent continuing tissue damage may be necessary.
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