tion of viable dermis is important in partial thickness injury whereas in full thickness injury all necrotic and infected tissue must be removed. The aim of debridement is to leave a viable wound bed of fat, fascia or muscle that will accept a skin graft.

Tangential excision of the burn wound was described by Janzekovic in the1970s [26] and involves repeated shaving of partial thickness burns in a tangential fashion using a skin graft knife or dermatome until a viable dermal bed is reached. This is manifested clinically by punctate bleeding. The more numerous the bleeding vessels in the wound bed, the more superficial the wound. Hemostasis is obtained with hot soaks and electrocautery and the wound is ready for grafting.

A hand skin graft knife or powered dermatome can be used to make serial passes across the wound to excise the full thickness wound. Excision can be aided by traction on the excised eschar as it passes through the knife or dermatome. Adequate excision is signaled by a viable bleeding wound bed, which is usually fat. The fat underneath must be viable and can be distinguished by its colour (red fat being dead fat), punctate hemorrhages, and thrombosed vessels. These appearances are all indicative of inadequate excision and necessitate further wound excision. After hemostasis the wound is ready for grafting.

Full thickness excision can also be achieved using sharp excision with a knife or with electrocautery. The plane of excision runs between viable and nonviable tissue, and an attempt is made to preserve viable subdermal structures and fat. This more controlled type of wound excision is used where contour preservation is important such as the face or where subcutaneous structures such as the dorsal veins in the hand require preservation.

Water jet hydro surgery (Versajet ) has been described and popularize for burn wound excision mainly in partial thickness injury [33]. Most reports have been anecdotal case series with only one comparative study. Authors cite precision and dermal preservation as the main benefits associate with this technique but accept longer surgical time as a drawback. The only randomized trial assessing this technology reported equivalent adequacy of debridement and shorter surgical time for the Versajet [34].

Fascial excision is reserved for deep burns extending down through the fat into muscle, late pres-

entation infected wounds and for failed initial surgery in patients with life-threatening invasive infections [35]. It involves surgical excision of the full thickness of the integument including the subcutaneous fat down to fascia. It is done with electrocautery and offers excellent control of blood loss and leaves a wound bed of fascia, which is an excellent bed for graft take. Unfortunately fascial excision is mutilating and leaves a permanent contour defect.

Avulsion can be used for some, deeper wounds particularly those treated conservatively. The necrotic eschar can be avulsed from the underlying viable tissue with minimal blood loss.

Occasionally primary amputation must be considered in management of the burn wound. It is usually reserved for high voltage electrical injuries or very deep thermal injuries with extensive muscle involvement and rhabdomyolysis which is life threatening. In general, limb salvage is attempted if possible with preservation of length to try and maximize function. Amputation in these cases is reserved for patients who have an ischemic limb or refractory invasive infection following repeated debridement. In other circumstances amputation is undertaken only if all other measures to preserve a useful functioning limb have failed.

Blood loss

Blood loss during burn surgery can be massive and pre-operative planning and preparation is required. The amount of blood required can be estimated. It depends on timing of the surgery post injury and the area of wound that requires excision and autografting.

The approximate blood loss in ml per cm2 burn excised in patients with burns > 30 TBSA is estimated as [31]:

Blood and blood products must be ordered and present in the operating theatre prior to the commence-