jury. Skin thickness varies based on anatomic location and on the sex and age of the individual. Eyelid and post auricular skin is very thin (approximately 0.5 mm thick). Men have thicker skin compared to women in all anatomic locations. Skin thickness varies with age with children having relatively thin skin. There is progressive thickening until the fourth or fifth decade of life following which the skin begins to thin again.

Mechanisms of facial burn injury are varied and are related to patient age and determine depth and outcome. In general the majority of partial thickness facial burns in children are following scald injury. In adults, usually males, the commonest cause is a flash burn and these tend to be partial thickness in nature and will often affect other exposed areas such as the hand. Full thickness facial burns tend to be flame related injuries in both children and adults usually as a result of a conflagration and are often associated with a large TBSA burn affecting other areas [2].

The characteristic edema secondary to release of inflammatory mediators both locally and systemically in bigger injuries can give rise to upper airway obstruction when associated with a facial burn. Not only is there a risk of upper airway compromise, there is also a well known association of facial burns with smoke inhalation injury.

As described elsewhere in this book the depth of burn injury is defined by the anatomical depth of tissue injury and is the major determinant of wound healing potential. Burn injury has traditionally been classified into epidermal, superficial partial thickness, deep partial thickness and full thickness burns. Each of these has differing potential for healing and for subsequent scar formation. Epidermal and superficial partial thickness burns should heal rapidly within 10–14 days and should not leave significant scarring. Deep partial thickness burns take over 3 weeks to heal and are associated with a high risk of hypertrophic scarring. Full thickness injury will not usually heal without surgical intervention.

Authors have correlated healing times to hypertrophic scarring [4, 5] and also to timing of surgery. Evidence shows that wounds healing within 14 days spontaneously have a very low incidence of hypertrophic scarring ( > 2%) and that surgical intervention is associated with a higher incidence of hypertrophic scarring up to 3 weeks following injury [5, 6].

Fig. 1. Facial aesthetic units (GonzalezUlloa 1987)

Most authors would now recommend timing of intervention between 10 to 21 days [5, 6]. However this data has been gathered and analyzed on burns occurring at all anatomical sites and as it is acknowledged that the face has improved healing potential further investigation is required into time to healing of facial burns in particular and subsequent scarring.

When considering facial burn injury it is vital to understand and remember the concept of aesthetic units and subunits first describe by Gonzalez Ulloa [7]. These units have consistent colour, texture, thickness and pliability, and can be divided into topographical subunits with a predictable contour which when used to plan placement of skin graft edges and subsequent scars can visually minimize the appearance of the scars (Fig. 1).

Management

General approach

The main goal in the management of facial burns is similar to that for all areas of the body.

The outcome of both facial and hand burns have a significant functional and psychosocial implication. Patients whose face and hands have been spared reintegrate more easily following burn injury. Deep burns of the face are devastating and requiring long-term psychosocial rehabilitation, physical therapy and multiple reconstructive procedures.

The aim of early wound healing, mobilization with preservation of form and function is as import-

Fig. 2. Facial burn treatment algorithm

ant in the face as anywhere else. Specifically in the face the burn team should aim to maintain facial architecture and preserve normal facial subunits, with acceptable or good anatomical balance and symmetry and a dynamic facial expression.

In principle the treatment algorithm for facial burn injury is relatively straight forward (Fig. 2). Management depends on the depth and size of the wound and the age and comorbidities of the patient. Superficial partial thickness wounds are left to heal spontaneously and those that are obviously full thickness undergo surgical excision and resurfacing with autograft. Deep partial thickness injury is usually best dealt with by tangiential excision and grafting [8] although some authors would favour a more conservative approach followed by aggressive scar management recognizing the limitations of facial grafting being suboptimal in terms of colour, texture and cosmetic outcome [3].

However it is the group in between that represent the true challenge in terms of optimizing healing and minimizing scarring. Burns that are of intermediate or indeterminate depth that may or may not heal within 3 weeks pose a difficult clinical problem with regards to preservation of aesthetic units and the development of hypertrophic scar. Most burns are mixed depth and if treated conservatively will give rise to patchy areas of hypertrophic scars that cross aesthetic unit boundaries.

In general a consensus view suggests a delay in the excision of acute indeterminate facial burns until days 7 to10 to allow better determination of the heal-

ing potential within a 3 week period. Adjunctive techniques such as the Laser Doppler that can help with burn depth estimation and potential for healing can be useful in this situation [9]. Once a decision is made to operate prevarication to ‘see if it will heal’ should be avoided as this usually leads to a prolonged period of wound dressing care with its attendant problems of pain infection and suboptimal scar formation.

Surgical excision of deep partialand full-thick- ness burns must be carefully planned and undertaken following strict principles including maintenance and preservation of aesthetic units, sacrifice of less injured tissue to preserve aesthetic units, bloodless surgery techniques, the use of allograft and or skin substitutes to optimize autograft take and early intense scar management [10].

Airway management

Patients with facial burns will often have an associated upper airway injury and / or lower airway injury requiring intubation and ventilation either in the before or soon after admission to the burn service. These patients can often require long-term intubation and ventilation. The presence of an endotracheal/nasotracheal/tracheostomy tube or indeed any tube can cause associated problems when managing the facial injury. In particular pressure from the tube or tube ties can cause pressure necrosis especially in the alar or collumellar regions but also of the lip and of the cheeks.