Introduction and Aetiology  

Burns are caused by coagulative destruction of the skin due to the transfer of heat to the body. If the heat absorbed is greater than the heat relesed, cell temperature rises, and may reach a degree where cell death occurs. There are three basic types of burn injuries which are thermal, chemical and electrical (24). Thermal burns are the most common and occur on contact with flames, hot liquid or steam. The severity of tissue destruction is proportional to the contact time, temperature and type of insult. The severity of a chemical burn is similarly related to the contact time with the skin, as well as the type, concentration and amount of chemical. Burns caused by alkaline chemicals tend to be more severe than acidic burns (24). Toxic fume inhalation can also lead to pulmonary dysfunction.

 

In electrical burns, dry skin has high resistance, whereas moist skin has less resistance. Blood vessels and nerves have low resistance and are good electrical conductors. Bone and muscle have higher resistance. Resistance to electrical flow leads to heat production. The skin is therefore able to better dissipate the energy better than deeper tissues. Contact with electrical currents produce tetanic muscle contractions, resulting in the release of an electrified object more difficult, prolonging contact time and leading to a more severe injury (24).  

 

Epidemiology

Burns are common injuries ranging in severity from small superficial scalds to full thickness flame burns, with high morbidity and mortality rates (32). In the UK, there are about 300 deaths from burns every year. About 250,000 people present to primary and secondary care with burns anually, though this is an underestimation as many small or innocuous burns are self-managed. About 12,000 patients are treated by specialist burns services in the UK each year, with about 500 of these injuries described as severe to complex and requiring urgent critical care at a regional burns centre (32).

 

The largest patient group to sustain burn injuries are boys under 2 years old, accounting for 12% of all injuries. Most are hot water and drink scalds sustained at home. The second largest group are males aged 25–34 years who account for 8% of all patients treated by specialist burns services. In children, adults and elderly patients, scalds now account for the bulk of all burns. The second common cause of burns are flame injuries, followed by contact burns (32).

 

Classification

Superficial burns involve the epidermis only and are red; like a sunburn. They do not blister and have a normal capillary refill and possess normal sensation. They heal normally and do not scar. Epidermal burns are excluded, when calculating the size of a burn.

Superficial partial thickness burns involve the epidermis and superficial (papillary) dermis and look pale pink. Blistering is a classic appearance of these injuries. Their capillary refill is normal and they are painful to touch due to exposed nerve endings. As long as they are kept clean and dressed appropriately, these scar very minimally and heal without the need for skin grafting.

 

Deep partial thickness burns extend into the deep (reticular) dermis and appear blotchy red. Capillary blanch is absent due to poor circulation within the skin. Sensation varies. Burn wound healing requires the presence of epidermal cells surrounding hair follicles, sebaceous glands and sweat glands to migrate over the wound and re-epithelialize it. As most of the glands have been burnt, they do not heal well without surgery. Full thickness burns involve the entire thickness of the skin and extend into the underlying fat and other tissues. They are either white or black and leathery to touch. They have no capillary blanch and are insensate. They require surgery to heal (24).

 

Pathophysiology

The integumentary system is composed of the skin, hair, nails, and exocrine glands. The inner zone of coagulative necrosis represents un-salvageable burnt tissue where the blood vessels are thrombosed and the skin is dead. The intermediate zone of stasis represents tissue affected by the burn with static blood flow. This area is amenable to first aid and good wound care. The wound is therefore salvageable if properly cared for (32). The outer zone of hyperaemia represents red, hyperaemic tissue that sustains minimal damage and usually recovers in 7-10 days (24). This is illustrated by Jackson's burn model below.

Minor burns: Burns are classified in severity according to two main factors: body surface area burned (BSAB) and the depth of the burn (27).

 

BSAB is initially a vital factor in determining systemic effects and whether IV and fluid resuscitation will be required. Estimation is done in many ways including Wallace’s Rule of Nines. Upon injury, blood vessels in and around the injured area dilate and their walls become more permeable. Fluid and proteins are therefore lost from the circulation resulting in venous stasis. Most of the fluid passes into tissues, leading to oedema. Some is lost from the surface of the skin as exudate, or into the skin as blisters. Therefore, the greater the area of the burn, the greater the fluid loss which may lead to hypovolemic shock (27).

Depth of burn is assessed by a combination of the history of the injury, clinical observation and pinprick sensation testing. Skin grafting should be considered for burns that do not heal within three weeks, as it will heal the full thickness burn quickly (27).  

 

Large burns: Patients with large burns need to be transferred to a burns centre for continued resuscitation and critical wound care. Fluid resuscitation ensures that all tissues are sufficiently perfused and the burn does not worsen due to hypovolaemia and hypotension. It should not be excessive, to avoid contributing to an already oedematous state. Oedema prevents adequate blood flow to the wound that is trying to heal. Burnt arms and legs should be elevated. Movement exercises are essential for maintaining strength, joint mobility and oedema prevention. Patients are nursed in single bedrooms to avoid the spread of infection and strict hygiene and infection control measures supplement wound care with regular showers and application of antimicrobial (silver based) dressings such as Acticoat. These patients require dietary support to prevent catabolism and maintain immune function. Nasogastric feeds or supplemental protein shakes can be used to supplement oral diet. Other gastrointestinal treatments include proton pump inhibitors to prevent gastric ulceration and prokinetics such as erythromycin or metoclopramide to maintain gastrointestinal motility (32).

 

 

 

 

 

 

 

 

 

 

 

 

 

Treatment 

All burns should have cool running water applied (a mixer tap with running water at 15°C is preferred) for 20 mins - 3 hours following the burn. Medicated gel sponges provide symptomatic pain relief but are not a substitute for running water first aid. The acute long term psychological effects should also be considered (24).

 

Dressings: Commonly used dressings are topical antimicrobials covered with a non-adherent impregnated gauze and a bulky gauze dressing. Infection is therefore controlled and the granulating wound bed is protected from trauma. Exudate is also absorbed. Heavily exuding wounds may benefit from an additional alginate dressing. Burn wound surfaces should not contact each other. Small, uninfected burns should be covered with sheet hydrogels or hydrocolloids. Small superficial uninfected burns can be covered with a semi-permeable film. Short-stretch compression bandages or self-adherent elastic wraps should be used for oedema control and to decrease scarring (24).  

 

Debridement: Most require repeated bouts of mechanical, sharp and/or enzymatic (e.g. collagenase) debridement. This will reduce the inflammatory response and chances of infection. It’s important to note that some topical agents, e.g. creams may form a film atop the wound and be mistaken for eschar. Bacterial colonisation should be avoided by removing foreign debris and facial hair in facial burns.

 

Infection control: Aseptic technique is adequate for smaller, superficial injuries. Antimicrobial therapy is standard in more severe burns. Systemic antibiotics aren’t generally administered prophylactically because concomitant hypovolaemia and reduced tissue perfusion is likely to compromise efficacy. Topical agents are used as a result. Silver sulfadiazine 1.0% cream is commonly used, followed by Mafenidine acetate cream (may cause stinging up to 30 mins after application). Clinical signs of a burn wound infection are similar to established signs, with increase in purulent drainage requiring more absorptive dressings. Previously red granulating tissue may become pale and there may be an increase in necrotic tissue. Common microorganisms found are S. pyogenes and S. aureus followed by P. aeruginosa, E. coli and Proteus infections. Here, treatment would include aggressive debridement and systemic antibiotics.

 

Pharmacological management: Pain (background, procedural or breakthrough) and anxiety in burn patients must be controlled, as some studies show that patients complain about these, in the first four days after injury. Pain in minor burns can be managed with NSAIDs, whereas severe burns may be managed with IV morphine. Anxiolytics e.g. benzodiazepines may decrease the need for painkillers as the perception of pain is exacerbated by anxiety. Patients also complain of itching in affected areas and is more common for lower extremity burns than upper extremity burns. Interestingly, facial burns don’t appear to cause pruritus. Lanolin-based creams, cocoa butter, vitamin E and aloe are routinely used to treat this presentation but are often inadequate. Antihistamines e.g. Benadryl are therefore used. 

 

Surgical interventions: include surgical debridement, Escharoctomy/ Fasciotomy, skin grafts and skin substitutes (24).