2.The zone of ischemia–represents an ongoing microvascular injury that surrounds the zone of necrosis. Following burn injury to the skin inflammatory mediators are released via the arachidonic acid pathway and inflammatory cells. These include

histamine, prostaglandins (PGE2), prostacyclins (PGI2), leucotrienes, thromboxanes, kinins, serotonin, catecholamines, free O2 radicals and platelet activating factor. Local action of these inflammatory mediators includes increase in microvascular permeability giving rise to oedema formation, microvascular stasis and thrombosis. These actions can lead to progressive injury and cell death leading to clinical deepening of the burn wound.

This process can be influenced by desiccation, infection and hypoperfusion of the burn wound. There is ongoing interest into the manipulation of this area of injury to preserve viable tissue and prevent progression of tissue necrosis.

3.The zone of inflammation (hyperaemia) surrounds zone of ischemia and is manifested by increased vascular permeability with extravasation of fluid from the intravascular to the interstitial space leading to oedema.

Assessment of the burn wound

Key to management of the adult burn patient is the formulation of a treatment plan. The burn wound must be assessed clinically before a treatment plan can be formulated. The depth of the burn wound, the size of the burn and the anatomical site of injury are all vitally important factors that must be assessed and considered in the treatment plan.

Depth of burn

This is determined mainly by clinical wound inspection. Determining the depth of the burn wound can be difficult. In general superficial partial thickness wounds are pink, moist, blistered, blanch on pressure and are very painful. Deep partial thickness burns will either be white or red with fixed staining. They do not blanch on pressure. Full thickness burns characteristically have a leathery appearance and are insensate. It is usually easy to diagnose a very superficial burn or a full thickness burn. Deep dermal burns can be a

little more difficult to assess and are often indeterminate on first assessment. Techniques such as Laser Doppler scanning can give an estimate of dermal blood flow and depth of burn injury. Healing times and timing of surgical have been correlated to the incidence of hypertrophic scarring. Wounds that heal spontaneously within 14 days have a very low incidence of hypertrophic scarring [3]. Surgical intervention is associated with a higher incidence of hypertrophic scarring up to 3 weeks following injury [4].

Size of the burn

This is usually represented as percent of total body surface area (%TBSA) injured using

a)Wallace’s “Rule of Nines” useful for initial rapid estimation in the emergency setting

b)Lund and Browder Chart for a more precise estimation

c)Patient’s palm ~ 1% of their body surface.

Initial management of the burn wound

A general systematic approach must be undertaken to manage fluid resuscitation, smoke inhalation and other injuries in the first instance. Maintenance of the airways, breathing and establishing venous access are paramount and are discussed in other chapters.

Following assessment of the depth, size and anatomical distribution of wound the following procedures should be considered:

First aid

Cooling the burn wound soon after the injury (within 30minutes) is beneficial in removing heat from the wound and limiting tissue damage. It can also reduce early oedema and protein extravasation. Care must be taken, as prolonged or excessive cooling can be detrimental and lead to hypothermia. Irrigating the wound in a drench shower for at least 20 minutes is essential in chemical injury to dilute the chemical [6].

Burn blisters

There is ongoing debate about management with evidence of blister fluid having both beneficial and

deleterious effects. In general blisters should be removed if large, over joints and if they produce functional impairment. Small intact blisters can be left in situ to act as a biological dressing. One of the key indications for blister removal is that the dermal wound beneath can be inspected and the depth diagnosed [7].

Escharotomy

Escharotomy is required in circumferential full thickness burns of chest, limbs or digits.

In limbs/digits such burns impair circulation, produce distal ischemia and can lead to compartment syndromes, digital and limb loss. Circumferential full-thickness chest burns can restrict chest wall excursion and impair ventilation.

Such burns require mid-axial escharotomies performed either at bedside or in the operating room. A scalpel or electrocautery device can be used to incise through the full thickness burns down to bulging fat. The incisions should extend into adjacent non burned or less deeply burned tissue. Since the wounds are full thickness, minimal analgesia or anaesthesia should be required, but extension into less damaged tissue can be very painful. Current humane practice involves anaesthesia for this procedure. The decision to perform escharotomy is a clinical one. In a full thickness burn an escharotomy incision should improve outcome with minimal risk as the area will require excision and grafting later on during treatment.

General care of the adult burn patient

Adult patients with major burn injuries must be managed in a dedicated facility used to looking after such complex problems. Patients requiring Intensive Care support should be managed in a Burn ICU. Recent analysis of the effects of burn centre volume and mortality revealed a complex relationship not only dependent on patient characteristics but also where the patient was treated [8].

Fluid resuscitation using Parkland formula is currently standard care and although fluid resuscitation is the cornerstone of acute burn management it is apparent that in most centres patients today are receiving more fluid per percent total body surface

area (TBSA) giving rise to the concept of ‘fluid creep’. It has been show that patients receiving larger volumes of resuscitation fluid are prone to increased complications and mortality [9].

Burn patients with respiratory failure may require ventilation using lung protective ventilation strategies designed to minimise shear and stress forces in the alveoli. Pressure limited low tidal volume ventilation is the currently favoured strategy although high frequency percussive ventilation based strategies are becoming increasingly popular especially for rescue ventilation. A recent trial comparing the two strategies showed similar clinical outcomes in burn patients with respiratory failure however a higher percentage of low tidal volume strategy patients required rescue ventilation [10].

Vascular access in adult burn patients can be a significant challenge. Obviously central venous catheters represent a risk in terms of catheter related blood stream infections. Central venous catheters in burn patients are usually change after about 7 days following insertion either to a new site or over a guide wire. A recent study showed no difference in the incidence of catheter-related bloodstream infections between lines placed by new site or by guide wire exchange. Subset analysis of adults in this study revealed rewires having less catheter related blood stream infections compared to new sites [11].

Other studies have shown the incidence of sepsis increasing with increasing number of central line days and increasing number of central line changes. No statistically significant difference in the incidence of sepsis between upper-and lower-body central line sites was demonstrated [12].

Other intensive care bundles routinely undertaken in general intensive care practise may also have benefits in care of critically ill burn patients. These included protocols for deep venous thrombosis prophylaxis, stress ulcer prophylaxis, daily weaning parameters, sedation holidays, elevation of the head-of-bed up at 30 degrees and tight glucose control. Implementing these care bundles into the burn critical care setting was associated with reduction in ventilator associated pneumonias, and blood stream infection rates and lower mortality [13].

The hypermetabolic response in critically ill burn patients is characterized by hyperdynamic circulatory, catabolic and immune system responses. En-

ergy and protein requirements are massive during critical illness and inadequate replacement can lead to multiorgan failure, increased susceptibility to infection, and death. Attenuation of the hypermetabolic response using pharmacologic modalities is an essential part of care of the severely injured adult burn patients.

Current modalities include beta-adrenergic blockade with propranolol, growth hormone, insu- lin-like growth factor, oxandralone and intensive insulin therapy [14].

Early nutritional support is an essential component of burn care to prevent ileus, stress ulceration, the effects of hypermetabolism and should be initiated as soon as possible following admission. Multicentre analysis has demonstrated that patients fed within 24hrs of injury had no increase in complications and a lower rate of wound infections and shorter ICU length of stay [15]. There are a variety of techniques in assessing nutritional requirements ranging from formulae based on the age and weight and the percentage burn to the use of indirect calorimetry and the respiratory quotient. Nutrition is usefully provided using high energy, high protein enteral feeds via the nasogastric or nasojejunal route.

Pain control in the burn population is an essential part of care yet control of pain remains a difficult task that is often inadequately performed. The adverse sequelae of inadequate pain control in the burn population have long been recognised. Burn pain is dynamic and has a peripheral and central component. A therapeutic plan for pain control must be dynamic and flexible to address background, breakthrough, procedural and post-operative pain. Regular, ongoing and documented pain assessment is key in directing this process. The simple analgesic paracetamol (acetaminophen) has both anti-pyretic and opioid-sparing properties and justly deserves its place in the pharmacological treatment of every burn patient Opioid analgesics provide the backbone of analgesia to burn patients but must be used judiciously (Fig. 1). Other centrally acting drugs such as ketamine and gabapentin are increasingly being used as opioid sparing adjuncts. Non-pharmacolog- ical methods such as distraction therapy can also play a role. Pain specialists must be integral part of the modern burn multi-disciplinary team and pain control must be given a high clinical priority [16].

Fig. 1. Acute pain guidelines (courtesy of Dr P Richardson MB FRCA)

Treatment planning

As with all areas in medicine treatment planning is key to successful outcome. Initially the size, site, and depth of the burn wound must be assessed whilst simultaneously undertaking initial urgent measures. A burn wound treatment plan must be formulated. This management plan will include conservative and surgical options depending on the individual patient and the type and site of the wound.

Treatment planning depends on the assessment of the factors described in Fig. 2.

In general, for superficial partial thickness wounds a more conservative approach is undertaken. A more aggressive surgical approach is best

Fig. 2. Patient factors to assess for treatment planning

for deeper wounds, to improve outcome and reduce morbidity in smaller injury and to improve survival in bigger injuries. This based on the surgical principle that excision of dead tissues saves lives.

Superficial partial thickness wound

The aim of management of this type of wounds is to promote rapid spontaneous re-epithelialisation with the minimum number of painful dressing changes and to prevent infection which can lead to deepening of the wound and subsequent increased risk of hypertrophic scarring.

The wounds can be treated either with biological or semi biological dressings, with topical antimicrobials, with standard dressings either impregnated or free from a topical agent or by exposure

Biological/Semi biological dressings

Biological dressings can be defined as the use of human or animal tissue for temporary wound covering. A semi biological dressing refers to where a component of the dressing is derived from such tissue (i. e. collagen).

Biobrane is a semibiological dressing made up of a fenestrated silicone layer bonded to a nylon mesh that has bee impregnated with Type I porcine collagen. It has been used in burn care for the past twenty years since its development. In randomised controlled studies its use has been shown to reduce pain, in patient stay and time to healing [17,18].

In patients presenting within 24h of their injury, following admission and stabilisation the patient’s burns blisters are cleaned, debrided and all burned epithelium is removed under sedation or anaesthesia. Biobrane is then applied to the wound in a circumferential fashion around the limb or trunk so that it is closely adherent to the wound. The Biobrane is secured by either by stapling it to itself or the use of sterile Hypafix tape. Care is taken not to staple the Biobrane to the patient as this can cause granulomas and the staples are painful to remove. The Biobrane is then wrapped with a standard dressing of rolled gauze covered by elastic bandages. The dressings are removed at 24–48 hrs to inspect the wound. Oral antibiotics with staphylococcal coverage are given for five

days. If the Biobrane is adherent after the first day, no further dressings are required. As re-epithelialisation occurs in 10–14 days the Biobrane spontaneously separates from the healed wound. If wound infection supervenes, the Biobrane rapidly becomes non adherent and can trap any exudate produced by the wound. For this reason Biobrane is not used in patients presenting more than 24–36h following their injury and in larger wounds (>40% TBSA). Biobrane is also relatively expensive compared to common topical antimicrobials.

Topical antimicrobials

Silver has been used as an antimicrobial agent for some time. Numerous silver containing dressings are currently used for the management of burn wounds.

Traditionally topical Silvadene/Flammazine (1% Silver Sulfadiazine) is the usual alternative for these wounds. After cleaning the wound and debridement of the blisters, Silvadene is applied topically to the wound which is then covered with rolled gauze and elasticated bandage. The Silvadene dressings are changed once or twice daily until re-epithe- lialisation occurs and the wound is healed. This method requires frequent dressing changes, which can be a painful.

Acticoat is a nanocrystalline silver dressing that can provide sustained release of silver for up to 7 days [19]. A randomised controlled trial compared Acticoat to Silver Sulfadiazine demonstrated Acticoat to have better antimicrobial activity compared to silver sulfadiazine [20]. Other studies have suggested Acticoat has fewer adverse effects and reduces healing times. It is easy to apply and requires low frequency of dressing changes makes it an ideal dressing in burn wounds [21]. It is the method of choice for patients presenting late after injury with a colonized wound.

Biological dressings

Biological dressings such as allograft skin, xenograft skin (porcine), human amnion can all be used in a similar fashion to Biobrane to physiologically close the wound while re-epithelialisation occurs. The problems associated with the use of these products