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Resident Orientation Manual

Produced by Galveston Shriners Burn Hospital and
The University of Texas Medical Branch Blocker Burn Unit.
Contributors:  Sally Abston MD, Patricia Blakeney PhD, Manubhai Desai MD,
Patricia Edgar RN, CIC,John P Heggers PhD, David N Herndon MD,
Marsha Hildreth RD, Ray J Nichols Jr. MD

 

CLOSURE OF THE BURN WOUND

   The ultimate solution of burn management is closure of the burn wound through surgical intervention.  The alternative burn-care philosophies differ in the timing of the surgical procedure.  The conservative approach awaits spontaneous separation of the burn eschar over 3-5 weeks.  Topical antimicrobial wound therapy is used for prevention of infection.  The resultant granulation bed is then skin grafted.  This method advocates maximal preservation of viable tissue.  However, conservative treatment increases the risk period for infection, fluid and electrolyte disturbances, and malnutrition.  The eschar is separated by the action of bacterial proteolytic enzymes, and the granulation bed is generally heavily colonized.  Prolongation of the inflammatory phase of wound healing can result in increased hypertrophic scarring.  This method is currently disfavored except for facial burns and small burns (<20% BSA).

   The alternative approach involves excisional therapy of the burn wound prior to spontaneous eschar separation.  A clinical comparison of conservative versus early excision demonstrated significant reductions in infectious complications and length of hospital stay in the latter group.  Excisional therapy may also reduce protein catabolism, immunosuppression, and evaporative water losses.  In some cases, early excision can improve cosmesis by reducing hypertrophic scarring.

   Timing of excisional therapy is debatable.  Some surgeons prefer excision 4 to 14 days post-burn when the acute resuscitation period is well over.  This may involve serial excision of various portions of the burn over days to weeks.  Other surgeons prefer early excision of the burn wound within 5 days of the injury prior to bacterial colonization of the wound.  In experimental models, complete excision of the wound within 24 hours of injury prevented hypermetabolism and immune suppression in the post-burn period.  Clinically, in children with greater than 60% BSA burns, excisional therapy resulted in improved survival.

   We recommend early excisional therapy of major burn wounds as soon as hemodynamic stability, physiological tolerance, and reliable determination of burn depth are ascertained.  In other words, the patient should undergo excisional therapy of full-thickness wounds when surgical risks do not increase risk of mortality nor compromise anticipated functional and cosmetic results.  Early accurate determination of burn depth can be difficult.  In scald burns, delay of excision for one week reduces blood loss and areas of skin grafting.  However, clinical determination of depth in most flame wounds in more readily apparent.  For most flame burns, excisional therapy can be completed within 48 hours of admission unless delayed by serious inhalation injury, concomitant injuries, frailty from extremes of age, or pre-existing medical conditions.  Partial-thickness flame burns that will spontaneously heal within 14-21 days are not excised.  If treated conservatively, deep partial-thickness burns produce poorer scars, more complications, and prolonged hospitalization.  If healing takes longer than 21 days, 78% will result in hypertrophic scar formation.  Therefore, deep partial-thickness wounds are often treated similar to full-thickness injuries.

Surgical Techniques
   First described by Janzekovic 20 years ago, tangential excision involves sequential removal of eschar in layers (0.010-0.025 in.) with a dermatome or guarded knife (Goulian, Humby, or Weck) until viable dermis or subcutaneous fat is reached.  An acceptable wound bed is identified by active punctate bleeding.  By using this technique, a maximum of viable tissue is preserved and optimal functional and cosmetic results are achieved.

   Fascial excision removes all layers of eschar and underlying tissue to the level of fascia.  Excision to this plane minimizes bleeding and provides a reliable, clean, vascular bed.  Fascial excision is recommended if the subcutaneous fat is burned, and in selected large burns with >60% BSA full-thickness who have high risks for infection, blood loss, or skin graft slough.  Fascial excision results in considerable cosmetic deformity.  For example, fascial truncal excision sacrifices the breast buds in pre-pubertal females.  Therefore, fascial excision is not used except in the worst burns.

   The extent of excision is determined by the stability of the patient, the speed of the surgical team, the adequacy of anesthesia, the rate of blood loss, and the availability of skin graft or its substitute.  Central venous access, an arterial line, a nasogastric tube, and a Foley catheter are needed for patient monitoring during the procedure.  Ketamine is the preferred anesthetic agent in children.  If ketamine is used, endotracheal intubation is not always needed.  Anticipated blood losses are 0.75 ml/cm² of area of excision during 2-16 days post-burn, or 0.40 ml/cm² if excision is performed during the first 24 hours.  Blood losses are minimized by use of tourniquets, pressure, topical thrombin, and topical or subcutaneous epinephrine.  Overdoses of epinephrine producing hypertension or paroxysmal tachycardia do occur with injudicious topical use, especially in children.  In burns <40% BSA, excision can be completed in a single procedure.

Skin Substitutes
   The early excision of the burn wound mandates early wound closure.  Preferably, closure is with permanent skin autograft, but closure can also be achieved with skin allograft, other biological dressings, or skin substitutes.  Without immediate closure, dessication or infection can increase tissue loss and negate the benefits of early excision.  In burns <40% TBSA, wide availability of donor sites permits wound closure with autograft.  Sheet grafts are always preferred for their improved cosmetic results.  In burns >40% BSA, donor sites are more limited.  Many unburned areas, e.g. the face, are unacceptable for graft harvest.  By meshing the grafts, better expansion ratios can be obtained for greater surface coverage at the price of reducing cosmesis.  Sheet grafts are always used for the face, neck, and hands when available.  Mesh expansion ratios larger than 4:1 result in sub-optimal healing and thin, easily damaged skin coverage, so are generally not used.  As described by Alexander, we cover our 4:1 meshed skin autografts with 2:1 meshed skin allograft to protect the wound beds during healing.  As the autograft heals and spreads underneath, the allograft is shed.  In massive burns (>70%), donor sites are severely restricted, prompting searches for an acceptable skin substitute.

   Unlike biologic dressings, skin substitutes become incorporated permanently, in part or as a whole, into the wound closure.  An artificial skin developed by Burke, et al (Integra©) is composed of an outer silastic 'epidermis' (0.1 mm thick) and an inner biodegradable bovine collagen glycosaminoglycan (GAG) based dermal analog.  The inner surface provides for good wound adherence while the outer layer prevents exogenous bacterial contamination and excessive evaporative losses.  After 26-30 days, fibroblasts and collagen at the GCG-wound interface organize into a neodermis.  The outer silastic layer is then gently peeled off and replaced with a 0.004 in. thick epidermal graft.

   Other dermal replacements include cultured allogenic fibroblasts and/or keratinocytes, decellularized human collagens, and other synthetics similar to Integra©.  Clinical trials of these substances are on-going.

   Using tissue culture techniques, human epithelial cells can be grown in vitro.  Over a period of 2 to 4 weeks, larger confluent multi-layered sheets of cultured keratinocytes are obtainable from a small patch of donor skin (see the policy and procedure manual for exact method of obtaining biopsies), its surface area coverage expanded 100 times or more.  Cultured epithelial autograft (CEA) has been successfully used to provide permanent wound closure in massively burned patients.  Unfortunately, wounds covered with just epidermis display poor skin function and continued wound contraction.  Resultant scars are not optimal.  The search for a suitable dermal epidermal skin replacement continues.  Combined use of CEA with either allograft cadaver dermis, cultured dermal fibroblasts, or a synthetic dermal analog may provide the ultimate solution for massive skin replacement.

 

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