This article reviews guidelines for burn wound excision, regarding timing, depth, and technique. The authors collect evidence from both animal models and the clinical literature, to recommend best practices for burn wound excision.
Key points
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The ability to evaluate burn depth is critical to planning surgical excision.
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Assessment of tissue viability is key to proper burn excision and can be achieved by evaluating for punctate bleeding, patent vessels, pearly white appearance of the dermis, absence of ecchymosis, and bright yellow fat.
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Early excision has improved outcomes by decreasing overall mortality, incidence of wound sepsis, and length of hospital stay.
Introduction
The management of burns is a multidisciplinary cooperation of all specialties from surgeons and nurses to therapists and nutritionists, and all who have patient contact. Unfortunately, burn wounds can lead to scarring, wound sepsis, and even death, mandating early, safe, and efficient treatment. The decisions to remove the burn tissue are critical to survival in many patients. The most important decision making in burns then, is deciding when to perform surgery and at what depth to debride for the most optimum healing and patient recovery.
Introduction
The management of burns is a multidisciplinary cooperation of all specialties from surgeons and nurses to therapists and nutritionists, and all who have patient contact. Unfortunately, burn wounds can lead to scarring, wound sepsis, and even death, mandating early, safe, and efficient treatment. The decisions to remove the burn tissue are critical to survival in many patients. The most important decision making in burns then, is deciding when to perform surgery and at what depth to debride for the most optimum healing and patient recovery.
Evaluation and depth of burn wounds
The surgical management of burn injury is influenced by the depth of injury. Superficial (first-degree) burns involve only epidermis and are treated entirely nonsurgically. Partial-thickness (second-degree) burns penetrate into the dermis with a variable depth. Superficial partial-thickness burns penetrate to the papillary dermis, whereas deep partial-thickness burns penetrate deeper into the reticular dermis. Partial-thickness burns have the ability to re-epithelialize naturally from stem cells surrounding the dermal appendages (hair follicles, sebaceous glands, sweat glands, and apocrine glands). Often times, superficial partial-thickness injury can be treated without excision and grafting, with expected healing within 10 to 14 days. Deep partial-thickness burns, however, often take longer to heal, with an increased incidence of hypertrophic scarring. Finally, full-thickness burns cause a level of injury down to subcutaneous fat, eradicating the dermal appendages and eliminating a source for cutaneous regeneration, therefore requiring surgical debridement and grafting.
When evaluating depth of burn injury, one must take into consideration the thickness of the skin layers in the area of injury, which can offer varying degrees of protection from thermal exposure. The epidermal thickness can vary from less than 1 mm in the genitalia and eyelids to greater than 10 mm on the back. The dermis also varies in thickness depending on the age of the patient, with thinner dermis present in children and elderly patients. Therefore, surgical management may vary based on the patient’s age and the location of the burn.
Burn wounds have been described as 3 concentric zones with varying tissue injury including a central zone of coagulation, a surrounding zone of stasis, and an outer zone of hyperemia. The zone of stasis is an ischemic, yet initially viable portion of skin that surrounds the nonviable zone of coagulation. This zone is particularly susceptible to insults that can induce conversion to nonviable tissue including improper resuscitation or delayed excision of burn eschar, causing inflammation or bacterial infection.
History of surgical management of burn wounds
Prior to the mid 1900s, the management of burn injuries was primarily medical, where wounds were treated with topical medications only. When full-thickness burns were treated nonsurgically, the natural progression was separation of the eschar from the underlying wound bed weeks to months after the initial insult. This left a granulating wound that was still in need of grafting or was allowed to scar in, leading to prolonged hospital stay, hypertrophic scarring, contractures, wound sepsis, multisystem organ failure, and at times death.
The paradigm shift toward early burn excision occurred in 1970 when Janzekovic showed improved patient outcomes with tangential excision and complete removal of necrotic tissue with autografting on the preserved well-vascularized deep tissue. This ground-breaking study showed a reduction in pain, total number of procedures for wound closure, and length of hospital stay. The study was followed by multiple others in support of early excision due to additional benefits including quicker healing, less incidence of hypertrophic scarring, decreased incidence of wound sepsis and need for antibiotics, and a greater than 3-fold decrease in mortality rate. Early excision had already become the standard of care when the relationship between burn eschar, inflammation, and systemic inflammatory response syndrome was discovered. Systemic instability was shown to be induced by inflammatory mediators from burn eschar, and this response can be attenuated with early excision. As the burn size approaches 15% to 20% total body surface area (TBSA), the inflammatory mediators are prevalent enough to cause a systemic inflammatory response, therefore justifying the need for massive fluid resuscitation to prevent conversion of burn and early excision to abort the inflammatory cascade.
Recent work on animal models has given further insight into the benefits of early burn wound excision. Although animals exhibit a much quicker capacity to heal burn wounds, they have contributed to the basic understanding of certain phases of the healing process in respect to people. Singer and colleagues have shown that tangential excision and grafting of full-thickness burns in a porcine model can decrease timing to heal as well as produce significantly thinner scars when performed early at day 2 versus later at day 14. Additional porcine studies have shown delayed excision and grafting to correlate with significantly worse Vancouver scar scale scores and increased fibrosis and alpha-smooth muscle, suggesting that delays in excision can increase incidence of hypertrophic scarring. Wang and colleagues used a rabbit model to show that tissue edema, wound contracture, and graft loss was significantly greatest when excision and grafting occurred at 18 to 24 hours, suggesting that it may be beneficial to perform excision and grafting either ultra-early or after 48 hours.
Burn injury has been shown to have suppressive effects on both the innate and adaptive immune response, leaving patients at risk for viral and bacterial infections. The effect of timing of excision on the immune system has therefore also been the target of animal models. Early complete excision of burn wounds in mice has been shown to restore cytotoxic lymphocyte function and viral-specific T lymphocyte cytotoxicity for the innate immune system. Immediate excision and grafting have also been shown to improve the adaptive immune system with restoration of antibody synthesis to bacterial antigens, suggesting that earlier excision may decrease risk of bacterial infections in burn patients. Fear and colleagues reported that early excision is less disruptive to the immune response by looking at markers for the innate and adaptive immune system. This study suggests that early excision during the phase of immune down-regulation initiated by the burn trauma maintains the innate and adaptive immune cell responses compared with delayed excision, which causes these to be down-regulated.
To this day, no exact recommendation for timing of early excision or safe percentage of burn to excise has been elucidated ( Table 1 ). Common practice is toward excision on postinjury day 3 to 5 due to the older recommendations by Janzekovic. Newer surveys suggest approximately 56% of burn surgeons will perform excision on postinjury day 1, and 57% will excise up to 20% TBSA at 1 time. Recent meta-analysis of randomized control trials looking at timing of excision show that excision between day 1 and day 6 is beneficial for mortality reduction in patients without inhalation injury and length of stay but increases the requirement for blood transfusion. Excision can be performed in a staged or complete fashion. Studies report safe total excision of all burn as early as the first 24 hours. Herndon and colleagues showed both staged and complete excision of large burns with immediate use of autograft and allograft to be safe and effective within 72 hours of injury.
| Ultra early | <24 h |
| Early | 24–96 h |
| Delayed | >96 h |
Burn wound excision
Preoperative Considerations
Planning for the surgical care of burn patients requires much thought. One must first consider intact skin for harvesting as well as recipient sites for the skin grafts. If there is little intact skin for harvesting, if possible, priority should be given to excision and grafting areas critical for central venous and arterial lines, tracheostomy sites, and gastrostomy sites, as patients with larger burns are expected to have a prolonged critical course with need for monitoring and long-term airway and nutritional supplementation. Larger areas not at high risk of contamination or shear may be considered next as engraftment is more likely. Getting early stable coverage may be critical in survival depending on the TBSA involved and the overall patient condition. Occasionally, priority is given to major joints or hands, since delays can lead to increased scar tissue formation and delayed range of motion during therapy, therefore causing an increased incidence of joint contractures. The exact order of burn excision is surgeon dependent but should be well planned and communicated to all parties involved to optimize outcomes.
Harvesting skin is performed with a dermatome and involves shaving of the epidermis and the superficial portion of the dermis. This leaves behind the remainder of the dermis to regenerate the epidermis through epidermal appendages; however, the dermis does not regenerate. Therefore, the thickness of the dermis at the harvest site should be taken into consideration, as it may limit the number of skin graft harvests one can take from a single site. If donor skin is limited, one may need to consider the need for skin harvest for growth of cultured epithelial autografts.
Patients with greater than 20% burns have an impaired ability for thermoregulation and therefore require close monitoring of body temperature. This loss of surface area able to contribute to thermoregulation, in addition to massive excision and blood loss, can contribute to temporary hypothermia intraoperatively. This can be countered by maintaining the ambient operative room temperature at 37° Celsius and keeping the patient covered with warm blankets, Bair huggers (3M, St Paul, MN), and the use of warmed intravenous fluids. Should the patient’s temperature drop below 35° C, coagulopathies may develop contributing to perioperative blood loss.
Types of Excision
The most important concept with excision of burn eschar is that debridement should be carried down to a level where only viable tissue remains. Burn wound excision can be performed as either tangential or fascial excision. Tangential excision is performed using a hand-held knife or dermatome that excises the burn eschar in a serial fashion to a depth of viable tissue capable of accepting a skin graft. This allows for preservation of as much viable tissue as possible with better contour and cosmesis than the fascial excision.
Fascial excision involves a full-thickness excision of skin and subcutaneous tissue down to the level of muscle fascia. Fascial excision is usually reserved for large, life-threatening burns where there is a need for rapid excision, or extremely deep full-thickness burns where only minimal fat is remaining. Advantages of this over tangential excision include its ease of dissection, limited blood loss, and a well-vascularized fascial layer for skin graft placement. Disadvantages include obvious contour deformities, permanent loss of all cutaneous sensation, and removal of viable subcutaneous elements including lymphatics, which can lead to bothersome lymphedema distal to the excision, precluding its use in the routine patient.
Tools Used for Excision
Prior to formal excisional debridement, mechanical debridement can be performed using a Norsen blade to remove pseudoeschar or eschar overlying burn wounds.
Tangential excision is mainly performed using hand-held knives: Weck, Watson, Goulian, Braitwaithe, or Humby blades. These are placed at the edge of the burn eschar with light pressure on the blade and used with a quick back-and-forth motion to pass across the length of the wound ( Fig. 1 ). Appropriate tension on the skin will assist with ease of uniformity of excision. Sequential passes can be made until a viable level of tissue is reached. Bovi electrocautery is used for fascial excision as well as to maintain hemostasis in tangential excision for larger punctate bleeding vessels.
