Chapter 25 Operative Exposure in Thermal Injury

This chapter will discuss basic management of thermal injury. Though the major emphasis of this lab experience is operative exposure, a brief review of the principles of diagnosis and management will also be presented.

Learning Objectives

By the end of the ASSET course, participants should be able to do the following:

1. Discuss the classification of thermal injuries.
2. Describe the ways to determine total body surface area of thermal injuries.
3. Discuss the initial management of thermally injured patients.
4. Describe the tools available for the surgical management of thermal injury.
5. Understand the indications for escharotomy.
6. Demonstrate the locations of incisions for escharotomies, when indicated.
7. Describe the steps of basic burn excision and grafting techniques.

Considerations

• Burns covering more than 20 percent of total body surface area (TBSA), or those with symptomatic inhalation injury, are lifethreatening.
• Standard of care for the management of lifethreatening burns is early consultation with and, if possible, prompt transfer to a burn specialist/ center.
• Hypothermia risk is high in burn patients, and immediate efforts should be made to preserve body heat.
• Historically, burns have been described by degree (first, second, and third) of injury, with second degree further divided into superficial and deep, and burns to deep muscle and bone described as “fourth” degree.
• Contemporary burn surgeons more commonly use an anatomic description based on the thickness or depth of the injury (Figure 1). (Мал. 1).
  • Superficial-thickness (first degree) burns (Figure 2) impact only the epidermal layer. These burns look like a mild or moderate sunburn, appear red, blanch easily, do not blister, and are painful to the touch. These wounds are not included in the TBSA estimation when calculating fluid resuscitation.

• Partial-thickness (second degree) burnscan be superficial—involving only the papillary dermis (Figures 2 and 3a)—or deep—involving both the papillary and reticular dermis (Figure 3b). These burns are moist, blistered, painful, and can blanche.

• Full-thickness (third degree) burns involve all epidermal and dermal layers and can include muscle and bone. These burns appear leathery and dry, are nonblanching, do not hurt, and often contain visible thrombosed vessels (Figure 4).
• The reticular dermis plays an important role in burn healing, and healing without surgical intervention (excision and grafting) is proportional to the amount of uninjured reticular dermis.
• A thorough history and physical examination is an important foundation for the management of thermal injuries. Knowing the mechanism (flame, scald, chemical, electrical, etc.) and the duration of contact will help guide management.
• Physical findings such as color, texture, and sensory changes are important parts of the exam and assist in determining burn depth.
• The initial assessment of burn thickness may not be the same as the final level of injury.
• Burn wounds evolve over time (Figure 5), with the ultimate depth of injury dependent on numerous factors that include adequacy of resuscitation, infection, and nutrition. As such, wounds must be frequently reassessed and care adjusted accordingly.
• Management planning can start with initial assessment of a burn injury but will often change as the wound progresses.

• In addition to wound depth, it is important to calculate the TBSA of the burn injury.
• A rough estimate of TBSA can be calculated using the “rule of nines,” as seen in Figure 6. TBSA assessments for children differ from adults, as children have proportionately larger heads and smaller extremities.
  • Significant over- or underestimation of burn wound size (by more than 10 percentage points) may lead to significant morbidity.
  • Underestimation may lead to underresuscitation and organ failure.
  • Overestimation may lead to resuscitation morbidity, such as pulmonary failure and compartment syndromes.
  • When wounds have been cleaned and debrided, the TBSA should be recalculated using the Lund-Browder burn chart, which allows for a more precise calculation.
• Another practical way to estimate TBSA is to use the patient’s hand (palm plus fingers) as one percent of TBSA (Figure 7).
• Once depth assessment is complete, wounds should be dressed as soon as possible with clean dry dressings, and the patient should be transferred to a burn care facility if they meet transfer criteria.
• If burn care facility transfer is delayed (more than 24 hours) or is not possible, consider coverage of the wound with a topical antimicrobial agent.
• If the TBSA is greater than 15–20 percent, initial care of thermal injury should be focused on the management of shock.
• The goal of burn-shock resuscitation is to replace burn-related fluid losses while avoiding over-resuscitation.
• Fluid resuscitation should start immediately via intravenous (IV) or intraosseous (IO) lines, which can be placed through burned skin if necessary.
• Current burn guidelines (U.S. Army Institute of Surgical Research) recommend resuscitation with IV isotonic crystalloids such as lactated Ringers or Plasma-Lyte, with volume and rate as follows:

• Boluses should not be given unless a patient is hypotensive.
• There is no role for “permissive hypotension” in a burned patient.
• IV infusion rate should be started at 500 mL/ hr while completing the initial assessment.
• Measure TBSA (partial and full–thickness burns only) and multiply by 10. This will determine the ongoing IV fluid rate. For example, if the patient has 40 percent TBSA burn, the rate will be 400 mL/hr.
• For patients greater than 80 kg, add an extra 100 mL/hr for each additional 10 kg.
• If resuscitation is delayed, do not try to “catch up” by giving extra fluids.
• For children, 3 × % TBSA × body weight (in kg) gives the volume (mL) to be given in the first 24 hours, with half to be given in first 8 hours.
• Place a Foley catheter for assessment of resuscitation.
• Urine output is the main indicator of resuscitation adequacy in burn shock. Fluid intake should be adjusted to maintain urine output at a rate of 30–50 mL/hr in adults and 0.5–1.0 mL/kg/hr in children (note that the child rate is given per kilogram per hour).
• Local wound care to prevent wound infection and treatment of pain are important in the initial management of thermal injuries.
• Escharotomies should be considered if a patient has circumferential (or near circumferential) full-thickness burns of an extremity or neck, or full-thickness burns of the anterior torso from midaxillary line to midaxillary line.
• Once burn shock has been resolved, excision of the burn wound should be performed using one of three techniques:
  • Simple excision and primary reepithelialization (for small burn wounds)
  • Tangential excision and split-thickness skin grafting
  • Polytrauma patients who are unstable may require fascial excision to minimize operative time and blood loss.

Position and Preparation

• The area for excision should be positioned for best exposure while also providing ample visualization of normal surrounding tissues.
• Wound preparation should be performed using chlorhexidine or Betadine solution.
• Escharotomies often have to be performed without the luxury of an available operating room.
• Temperature regulation is paramount in burn patients. OR temperatures should be as high as possible, and areas not undergoing excision should be covered in plastic underneath cloth drapes to preserve body heat.
• Hemostasis during burn excision requires a multipronged approach:
  • Tourniquets should be used for extremity excisions whenever possible.
  • Epinephrine should be added to warm saline solution at a concentration of 2 ampules per liter normal saline. Laparotomy pads soaked in this solution are liberally applied throughout the process for hemostasis.
  • Topical thrombin should be available for application after excision of burn tissue.
  • Electrocautery should be used sparingly for areas of bleeding that do not stop after three or four rounds of epinephrine/thrombin/ pressure wrapping.

Equipment

• A scalpel or Bovie electrocautery can be used for excisions with primary closure, fascial excisions, and escharotomies.
• The equipment seen in Figure 8 includes dermatomes for tangential excision and harvesting of donor skin. Noticeable differences between dermatome types include the width of a single pass and the depth of tissue excised. Note that all dermatomes can be used both for harvesting donor skin and for excising injured tissue.

Surgical Exposure

Escharotomy Assessment

• Full-thickness circumferential and nearcircumferential skin burns result in the formation of eschar.
• Eschar can lead to significant compromise of chest wall excursion in the case of thoracic burns and impairment of underlying tissue perfusion with accumulation of burn-associated extracellular and extravascular fluid within confined anatomic spaces.
• Escharotomy is surgical division of nonviable eschar, which allows the cutaneous envelope to become more compliant. This allows underlying tissue to expand and thereby prevent further tissue injury or functional compromise.
• Escharotomy is considered an emergent procedure in the treatment of burned patients, but it rarely needs to be performed in the emergency department at the time of initial presentation.
• Indications for emergency escharotomy are the presence of a circumferential (or nearcircumferential) eschar with one of the following:
  • Impending or established vascular compromise of the extremities or digits
  • Impending or established respiratory compromise due to circumferential torso burns
  • Impending or established abdominal compartment syndrome associated with abdominal burns
• Severely burned extremities should be immediately elevated at or above the level of the heart.
• Frequent range-of-motion exercises, as tolerated by the patient, can help minimize tissue edema and elevated tissue pressure.
• Any change in capillary refill time, decrease in Doppler signal, or change in sensation should lead to reevaluation of compartment pressures, with low threshold to perform immediate decompression via escharotomy and fasciotomy, if needed.
  • Markers of physiologic distress in a burned extremity parallel those of compartment syndromes developing for other reasons. Skin pallor as a sign is unreliable in thermal injury, as the color of burned skin may not change with vascular compromise.
  • Neurologic changes such as numbness, tingling, and paresthesia are more reliable than changes in skin color.
  • Markers of physiologic distress in the chest include increasing peak airway pressures or lower delivered tidal volumes for a set pressure.
  • Many patients who require escharotomy will not be able to interact for a complete physical exam. Therefore, a high index of suspicion for compromise and a low threshold for intervention should be maintained.
• It is important to realize that a subset of burn patients will need fasciotomies as their primary intervention for true compartment syndromes (see chapter 5 on extremity compartment syndromes).

Escharotomy Technique

• Escharotomies should be performed in as clean an environment as possible. Required equipment includes a scalpel, hemostats, ties, and electrocautery if available.
• Classic lines for escharotomy incisions are seen in Figure 9. It is helpful to mark them out on the patient beforehand, especially over the arm, to avoid inadvertent involvement of a joint.
  • Avoid exposing major neurovascular structures.
  • Never place escharotomy incisions on the palmar surfaces of the hands or the soles of the feet.
  • Escharotomies to address increased chest wall resistance and pulmonary problems should include abdominal wall escharotomies (Figure 10) if the abdomen is affected.

• Escharotomies of the extremities should be placed in a manner that will facilitate fasciotomy (if needed) and extend beyond the areas of full-thickness injury (Figure 11).
• Escharotomies for the hand should start with radial and ulnar releases along the thenar and hypothenar eminences (similar to the skin incisions performed for compartment syndrome of the hand), as seen in Figure 12. If these are insufficient, dorsal incisions between the metacarpal bones can also be performed.
• If needed, foot escharotomy is also performed with skin incisions similar to those used for fasciotomy, as described in chapter 5.

• Incision into the eschar should result in a significant split of the involved tissue; this is similar to the bulging of tissue from a fasciotomy incision (Figure 13).
  • It is important to fully divide the eschar, including the hypodermis, to allow for full expansion of the tissue.
  • It is also important to extend the escharotomy incisions beyond the edges of the eschar to prevent a tight constricting band and subsequent failure to decompress the underlying tissues.

Fascial Excision

• Fascial excision removes all levels of eschar and underlying tissues down to the level of the fascia but does not include excision of the fascia itself.
• Fascial excision is recommended when subcutaneous fat is burned and in select large burns that have a high risk for infection, significant blood loss, or loss of skin graft.
• A plane can be developed along the fascia of the anatomic area, using electrocautery or suture ligation to control perforating vessels (Figure 14).
• Once the excision is complete, redress the wound using standard antimicrobial dressings.

Tangential Excision and Grafting

• Excision of burn tissue and replacement with autologous skin (autograft) is a cornerstone of burn reconstruction.
  • Fundamental principles include:
    • Excision of all dead tissue
    • Adequate hemostasis
    • Prevention of shear injury through fixation of the graft
  • Significant blood loss can be expected and can challenge a resource-poor environment.
  • Burn excision is typically not recommended for patients who can be transferred to a burn center within one to two weeks of their injury.
• Positioning and preparation are discussed in the previous section.
• Adequate counter-tension is necessary to achieve optimal depth of excision:
  • Areas that are not amenable to countertension (torso, large thighs) can be excised by picking up a small segment to bring it into the path of the blade or by having assistants apply local pressure sequentially around the borders of the excision (Figure 15).
• A Weck or Humby knife (Figure 8) is held in the dominant hand (handle in the palm, loosely held by the fingers, with the index finger and thumb at the most proximal portion of the handle) and engages with the area of burn to be excised at approximate a 45° angle. Gentle, back and forth movements while progressing along the length of the wound result in excision of a uniform layer of tissue.
• Once an area is completely excised, the wound bed should bleed uniformly if dermis is still present; if fat is visible, there should be no evidence of hemorrhage.
  • Note that if vessels underlying the dermis can be visualized and do not blanch (i.e., are clotted), the overlying dermis has been irreparably damaged and must be removed.
  • Bleeding can be quite extensive during a large excision. Segmental excision with application of thrombin followed by wrapping with epinephrine-soaked gauze pads to provide pressure is advised.
• Once hemostasis is complete, skin grafts can be applied to the region requiring coverage.
  • Split-thickness skin grafts are taken at a depth of 0.008 to 0.012 inches (approximately to the thickness of the beveled end of a 10 scalpel blade).
  • Harvesting of skin can be done with any dermatome (Figure 16). Subdermal clysis of dilute epinephrine solution can make harvesting easier in some regions (the scalp in particular) but is not necessary.

• Once harvested, grafts can be applied directly (sheet graft) or meshed at ratios of 1.5:1 up to 6:1 (Figure 17). Smaller-meshed grafts are applied to areas of function (Figure 18), while broader-meshed grafts are useful for covering large areas (Figure 19).
• After application, it is important to fixate the graft to prevent shear injury (Figures 18–21).
  • Absorbable sutures or staples can be used to decrease movement of the graft, but true fixation comes from a compressive dressing.
  • Initially, nonadherent dressing layers are placed over the skin graft.
  • A tie-over bolster dressing can be constructed by placing sutures at one inch intervals around the outer edge of the graft and using them to firmly tie down fluffed cotton that is laid over the top of the nonadherent dressing (Figures 19 and 20).
  • Alternatively, negative-pressure wound devices can be used for graft stabilization (Figure 20) and are especially helpful for areas where movement is hard to prevent.