Jeffrey S. Guy
Presentation
You are informed of a patient who is being transported to your facility. By report, the patient is a 22-year-old male who was involved in an explosion of a small building suspected to be a methamphetamine lab. Prehospital providers report that the patient is awake and breathing spontaneously. He has burns on the front of his chest, abdomen, and bilateral legs from his groin to his toes.
Differential Diagnosis
Making a differential diagnosis for a burn injury may seem odd to some. After all the diagnosis of a burn injury should be obvious to most, including those with minimal medical training. The hazard in caring for those with burn injury is essentially becoming entranced in the grotesque nature of the burn injury and not identifying occult potential life threats in a timely fashion.
In structure fires, victims may be hit by falling debris, fall through collapsing floors, or escape upper floors by jumping through windows. Patients may get burned after a motor vehicle crash (MVC), and focusing on the burn may delay rapid and appropriate treatment of commonly encountered traumatic injuries. Patients presenting with major burn injuries should undergo a methodical evaluation for traumatic injuries employing the concepts taught in advanced trauma life support (ATLS). Any injury that can occur following a fall, assault, or MVC should be sought in a burned patient.
The most dreaded complication in the early management of the burned patient is loss of the patency of the airway from airway edema. Failure to detect airway edema in a timely fashion can be catastrophic.
In this case, the patient may likely to have been exposed to hazardous materials and be at risk for a chemical burn. A patient contaminated with hazardous materials presents unique challenges to the medical providers as well as the receiving institution. If the patient inadequately decontaminated, bringing the patient into the hospital emergency department (ED) risks the safety of the medical providers as well as other patients within the ED. A contaminated patient must be decontaminated prior to entry into the ED, and providers providing decontamination and medical care during this phase of care must don appropriate level of personal protective equipment.
Chemical burns that are not adequately decontaminated will continue to cause injury to the patient during transport to the hospital and evaluation within the ED. Therefore, appropriate contamination needs to be immediate and of an adequate magnitude to reduce the risk of ongoing tissue injury or systemic toxicity to the patient. If a contaminated patient is brought into the ED, the safety of other patients, visitors, is jeopardized. Furthermore, contamination of the health care facility can cause closure of the ED until it can be made safe by decontamination.
Workup
The initial evaluation and treatment of the burned victim should follow the principles taught in ATLS. A systemic evaluation to identify and treat immediate life threats is then followed by a head-to-toe examination. Often, providers not experienced in caring for severe burns may focus on the horrific nature of the sights and smells associated with the burn. This mistake is similar to that which is commonly made in the evaluation of the pregnant trauma patient; providers will commonly and erroneously center their evaluation on the fetus instead of the more immediate life-threatening injury to the mother.
All clothing and jewelry must be removed as these may retain residual heat and continue to injure the patient. In the early hours after a burn injury, accurate determination of burn depth is deceptively difficult. Some burns are easily determined as full thickness, while others are more indeterminate.
The patient needs to be fully exposed to quantify the magnitude of the burn injury. To fully determine the size of the burns, the burns will require local debridement. Prior to debridement, the burn often appears more superficial than it actually is. Another problem occurs when a provider erroneously determines that a normal or a superficially injured area is blackened by soot.
Local wound debridement prior to arrival at the burn center may not be appropriate, but providers should take measures to accurately estimate burn size. Underestimations of burn size will likely lead to inadequate fluid resuscitation and complications of prolonged hypovolemic shock. Overestimation of burn size will produce the complication of excessive fluid administration.
Diagnosis and Treatment
Perhaps to many, making the diagnosis of a burn would seem rather straightforward. However, with an injury of this magnitude, there are several limb- and life-threatening complications that can develop rapidly. In addition to the diagnosis of “burn,” the patient might also develop (1) toxic asphyxiation, (2) airway obstruction, (3) smoke inhalation, (4) circumferential burns of the torso preventing respiration, or (5) limb-threatening limb ischemia from circumferential limb burns. Furthermore, appropriate triage and fluid treatment depend on accurately estimating burn size.
Airway
The highest priority is for the provider to determine the patency of the airway. Following an inhalation injury, the mucosa of the trachea can become edematous increasing the patient’s work of breathing, as well as the patency of the airway lumen. Inhalation injury should be suspected in patients with burns to the face or chest, singeing of facial hair, soot in the mouth or sputum, or change in the character of their voice. A patient with swelling of the upper airway or epiglottis will have drooling, and seek a sitting, forward-leaning position. If airway edema is a concern, the patient should be intubated.
Smoke Inhalation
The leading cause of death from structure fires is complications from smoke inhalation. However, smoke injury, when it is the only injury, has a mortality rate of <10%. When combined with burn injuries, the mortality of smoke inhalation increases to 20%. The presence or absence smoke inhalation is a greater predictor of survival than the size of the burn or the age of the patient. The diagnosis of smoke inhalation should be considered in patients who were in structure fires or were rescued from an enclosed space fire. The presence of soot in the sputum is known as carbonaceous sputum. Bronchoscopy is commonly used to identify soot below the level of the vocal cords and confirm smoke inhalation.
Burned patients who present with a decreased mental status are likely to have experienced some magnitude of asphyxiation or intoxication. Fire requires heat, oxygen, and fuel. In a structure fire, the flames consume the oxygen in the environment and produce several toxic gases. In a structure fire, the percentage of oxygen in the ambient environment is frequently less than the ambient 21%. Also, two asphyxiates associated with structure fires are carbon monoxide and hydrogen cyanide (HCN).
Carbon monoxide (CO) is a colorless, odorless gas that binds with hemoglobin more than 210 times stronger than oxygen. Patients who have been involved in structure fires may suffer from carbon monoxide toxicity. CO toxicity is the leading cause of poisoning deaths in the United States. The symptoms of CO toxicity are nonspecific and include headaches, nausea, and dizziness. In the most severe cases of CO poisoning, patients will experience weakness, seizures, coma, arrhythmias, hypotension, and eventually death.
The complex of carbon monoxide and hemoglobin is known as carboxyhemoglobin. On room air, the half-life of carboxyhemoglobin is 250 minutes. On 100% oxygen by an endotracheal tube, the half-life is reduced to 60 minutes. With hyperbaric oxygen at two atmospheres, the half-life is reduced to 27 minutes.
A patient with thermal injuries, smoke inhalation, and carbon monoxide toxicity requires complex and aggressive care by experienced providers. Use of hyperbaric oxygen remains controversial and of questionable benefit in such critically injured patients. At present time, there is universal agreement that application of 100% oxygen is beneficial to these patients.
Cyanide Toxicity
HCN is produced from the burning of many materials in the environment. HCN poisons cellular respiration at the level of the electron transport chain or oxidative phosphorylation. The net result is anaerobic metabolism and the development of lactic acidosis. A simple chemical laboratory test is presently lacking; however, most medical centers send a sample to a reference lab to obtain plasma cyanide levels. The treatment of suspected cyanide poisoning must occur rapidly. Given the absence of confirmatory laboratory tests, medical providers must make a decision to treat for cyanide poisoning based on the historical information and nonspecific metabolic findings. In the event of cyanide toxicity, the patient may demonstrate lactic acidosis and an increase in oxygen saturation on the venous blood gas.
Rapid treatment of suspected cyanide poisoning is required to avoid neurologic complications or death. The modern treatment includes the use of hydroxocobalamin (Cyanokit), which is an analogue of vitamin B12. This modern antidote chelates the cyanide. This antidote is well tolerated, but has the peculiar side effect of causing a red discoloration of the skin and urine. Hydroxocobalamin interferes with the accuracy of many common laboratory tests, such as electrolyte and hepatic panels.
Burn Depth
Burn depth determination is deceptively difficult. The appearance of the burns can change dramatically in the first 48 hours. Burn depth is categorized based on the anatomical regions of the skin injured. Superficial burns (first degree) involve only the epidermis, typically appears as reddened skin, and will heal typically within a week with minimal treatment. Partial-thickness burns (second-degree burns) involve the epidermis and varying depth of the underlying dermis. Partial-thickness burns will blister and will have a red glistening appearance of the wound beds.
These wounds may take 2 to 3 weeks to close and may produce some degree of scarring. Partial-thickness burns may require surgery. Full-thickness burns are characterized by destruction of both the epidermis and the dermis and will commonly appear as white, gray, or black and are leathery in texture.
Burn Size Estimation
In adults, perhaps the easiest and best-known method of determining burn size is the rule of nines. Each major body region comprises approximately 9% of the total body surface area (TBSA). This rule does not apply to children because children have differing body proportions that change as the child ages. For instance, infants have proportionally larger heads and smaller lower extremities compared to an adult. To estimate burn size in children, a diagram such as the Lund-Browder chart is required.
Perhaps the most commonly deployed method of determining burn size in adults is the rule of nines. The premise of the rule of nines is that in adults each major body region is approximately 9% TBSA. These major regions include entire head, entire arm, anterior chest, posterior chest, anterior abdomen, posterior abdomen, thigh, and lower leg. The entire palm of the patient (not the palm of the provider) approximates 1% of the TBSA. The area of the genitalia also approximates 1% TBSA.
Fluid Resuscitation
Most providers are aware that a burn injury is capable of producing severe and even life-threatening hypovolemia. After a major burn injury, the walls of the capillaries lose integrity and predispose the victim to hypovolemia. This loss of intravascular fluid from the microcirculation is often called leaky capillary syndrome. This is initiated by the release of proinflammatory mediators and reactive oxygen species from the nonviable burned tissue. The overall biologic effect of these mediators includes microvascular changes consistent with capillary leak syndrome, vascular stasis, and decreased cardiac output. Baxter et al. demonstrated that burned animals had a decrease in measured cardiac output that is refractory to treatment with intravenous fluid, vasopressors, and inotropic support. Myocardial depression typically improves in 4 to 8 hours from the time of injury.
Presentation Continued
This patient was described as being burned on the anterior trunk (both chest and abdomen) and both legs from groin to toes. Applying the rule of nines to determine estimated burn size, this patient has 54% TBSA burn.
The resuscitation of burn shock is a reactionary therapy to the pathophysiologic response to a severe injury. Burn resuscitation does nothing to abrogate or reverse the pathophysiologic events that created the burn shock. There are several formulae that can be used to estimate the amount of fluids and rates required to treat burn shock. What all of the formulae have in common is the changing fluid requirements of the patient in the first several hours after burn injury.
To calculate a patient’s resuscitative fluid needs, one needs the weight of the patient in kilograms and the percent body surface area burned (% TBSA). Perhaps the most well-known and applied resuscitation formula is the Parkland. Applying this formula, the amount of fluid administered to the victim is 4 mL/kg/% TBSA burn. One-half of the total calculated fluid needs are administered in the first 8 hours after the injury. Therefore, if the patient does receive therapy for the first 2 hours after the injury, the first half of the fluids should be administered over 6 hours. The second half of the calculated fluid need is given in remaining 16 hours.
Our patient is an 80-kg male who has a 54% TBSA burn at midnight. Calculating a Parkland formula would look like the following:
Total 24 hour fluid needed:
4 mL/kg/% burn or 80 kg × 54% burn = 17,280 mL over 24 hours
Fluid needed from midnight to 8:00 AM—first 8 hours from injury/first 8 hours of resuscitation
17,280 mL/2 = 8,640 mL first 8 hours
8,640 mL/8 h = 1,080 mL/h
Fluid needed from 8:00 AM to midnight—hours 8 to 24
17,280 mL/2 = 8,640 mL for remaining 16 hours
8,640 mL/16 h = 540 mL/h
If the same patient who was burned at midnight but required 2 hours of transport only received 500 mL prior to arrival at the burn center.
17,280 mL/2 = 8,640 mL first 8 hours
8,640 mL – 500 mL = 8,140 mL
8,140/6 h = 1357 mL/h
Formal fluid resuscitation is typically reserved for those patients with burns >20% TBSA; only burns of this severity are associated with the capillary leak syndrome. For burns <20%, patients can commonly be managed by providing them with 150% of their calculated maintenance rate.
Adequacy of resuscitation is usually determined by urine output and systemic blood pressure. Placement of a Foley catheter is appropriate to evaluate the urine output on an hourly basis. A urine output of 0.5 mL/kg/hr is usually adequate. To avoid complications of excessive fluid administration, consider decreasing the fluid rate when the urine output exceeds 1 mL/kg/hr. In children and the elderly, one should strive for the urine output to be at least 1 mL/kg/hr since the kidneys of these patients have a decreased ability to concentrate solutes. The most commonly used fluid for burn resuscitation is Lactate Ringers. Many burn providers avoid normal saline because large volumes of saline are associated with the development of a hyperchloremic metabolic acidosis.
Circumferential Burns
Skin that has sustained full-thickness burns contracts and is less elastic than normal skin. Circumferential burns of the limbs are limb threatening, and circumferential burns of the thorax are life threatening. In the case of thoracic burns, the skin contracts around the torso and produces a profound decrease is chest wall compliance. When an intubated patient is on volume mode ventilation, a marked increase in the peak inspiratory pressure may occur. When ventilating the patient with an Ambu bag, the bag will be rigid and near impossible to compress. With time and ongoing fluid resuscitation, this will progress increasing the patient’s work of breathing to the point of respiratory embarrassment. Escharotomy of chest wall burns produces an immediate and profound improvement in compliance and improves ability to ventilate. When performing escharotomies on a ventilated patient, pressure control modes should be avoided because once the escharotomy incision have been made, the immediate improvement in chest wall compliance may produce a marked increase in tidal volume and risk of pneumothorax.
With circumferential burns of the limb, the burn eschar contracts while the underlying tissues are becoming edematous. This causes obstruction of venous outflow of the burned limb while the arterial flow remains open. This amplifies the rate of edema formation up to the point where the arterial inflow is obstructed. Escharotomy of the limb is required to reestablish distal blood flow and maintain limb viability.
Surgical Approach
Escharotomies
Limb escharotomies should be done in a timely fashion, typically within 4 hours of injury, to reduce the likelihood of limb-threatening ischemia. With circumferential burns of the chest, decompressive escharotomies may need to be performed rapidly to avoid respiratory embarrassment where patients are unable to be ventilated.
On limbs, escharotomies can be performed readily with an electrocautery. The incisions should be positioned on the true medial and lateral aspects of the limb. In a severely burned arm, the true anatomic position the arm occurs when the arm is held with the palm up. Escharotomies of the hands should be done after consultation with the receiving burn center.
Escharotomies of circumferential chest wall burns will produce an almost immediate increased in chest wall compliance. When patients are being mechanically ventilated with a pressure-control mode, failure to anticipate improvement in chest wall compliance will result in pulmonary barotrauma.
Burn Excision
Full-thickness burns are necrotic tissue, and this dead tissue is the source of significant systemic effects causing the patient to be profoundly ill. Early surgical excision of the burn wound will reduce both morbidity and mortality.
The details of the burn excision will vary with the anatomical region of the body burned, the age of the patient, as well as the overall physiologic status of the patient. Operative care of the large burns should only occur in specialized centers with a large volume of experience providing both the operative and the perioperative care to these types of patients. A general rule for burn excision has been to limit the operative time to <2 hours to limit both blood loss and hypothermia. Patients are then returned to the operating room every 24 to 48 hours until all the burn has been excised.
The timing of surgery with patients with smoke inhalation is complicated by the “honeymoon” period experienced by these patients. With smoke inhalation, the patients will have a period of 48 to 72 hours prior to developing significant pulmonary problems that may complicate transport to the operating room, as well as increasing the hazards of performing such an operation. Therefore, in patients with smoke inhalation, one should attempt to surgically excise as much as burn as safely possible prior to the respiratory status deteriorating.
In patients with critical burns, early trips to the operating rooms should remove the greatest mass of burned tissue. Early trips to the operating room should focus on those anatomical areas that allow for both rapid and large debridement. Excision of burns from areas such as the hands, feet, or face should be delayed because these areas take considerably greater time to perform a careful excision. Areas that require more time for excision are usually delayed until the patient is in a more favorable physiologic state.
Burn excision can be associated with considerable blood loss; therefore, attempts to limit hemorrhage should be made. Tourniquets and topical hemostatic agents should be deployed whenever feasible. Burn patients easily become hypothermic and typically large areas of the body are exposed during operative procedures. All maneuvers to maintain the patient’s body temperature should be deployed.
Once the burn wounds have been excised, the surgeon has numerous options for closure of the wounds. Preservation of patient function is more important than cosmetic outcome. A functional outcome that the patient can use for performance of activities of daily living is more important than producing an outstanding-looking hand that is essentially useless to the patient.
Donor skin is taken with various depths based on the area to be covered as well as the need to possible reharvest the site in the case of larger burns. Skin grafts that are taken very thin are perhaps more likely to take on the wound bed, but due to the small amount of dermal tissue in the skin graft, the amount of contracture of the graft will be greater. Donor sites taken thicker will have more dermis and will contract less; therefore, these types of thicker grafts are more desirable in areas of high mobility, such as the hands, antecubital fossa, neck, and face. Donor sites are typically taken at 0.010 to 0.012 inch thick, and for areas needing thicker grafts the thickness is commonly 0.018 inch. As a general rule, donor sites taken at 0.010 inch take about 10 to 14 days to heal.
A skin graft that is applied in a sheet fashion will commonly contract about 30%, and a graft that is meshed 1.5:1 will commonly retain the original size of the donor site. Faces and necks are universally grafted with thick sheet grafts or full-thickness grafts. Hands are commonly grafted with either sheet or nonexpanded 1:1 split-thickness grafts. Expanded mesh grafts are used to a variable degree based on the amount of donor sites available for harvest and the areas to be grafted.
Over the past 15 years, the use of dermal implants has increased in the acute operative care of the burn wound. A split-thickness skin graft has the entire epidermal layer and varying thickness of the dermis. The thicker the dermis the greater time required for the donor site to heal, but greater dermis means less contracture of the grafts and a greater functional outcome. Dermal implants are commonly considered for use in areas of high function or cosmetic considerations. There are two dermal implants used for autografting, one biologic and one synthetic. When a dermal substitute is used, a staged operative approach is used. During the first operation, the wound is excised and the dermal substitute applied to the wound bed. Following an interval to allow the implant to vascularize, autografts are applied over the dermal substitute (Table 1).
TABLE 1. Key Technical Steps and Potential Pitfalls in Burn Excision
Postoperative Management
The success of a technical procedure in the operating room is highly dependent on the care provided after surgery. Meticulous nursing care and therapy by experienced providers is required to optimize the functional outcome for the patient. Performing operative care on a burn patient at an institution not equipped to provide this high level of specialized postoperative care will result in poorer results. In the early postoperative period, unit protocols focusing on wound care and therapeutic positioning are designed to increase grafting success and maximize range of motion of injured areas.
Following autografting, the wounds are dressed with topical antibiotics and complex dressings. When dressing a fresh skin graft, the layer immediately adjacent to the graft is a nonadherent layer such as Adaptic, Xeroform, Vaseline gauze, or fine mesh gauze. The next layer typically consists of an antibiotic layer followed by several rolls of Kerlix to serve as an antishear layer and finally a layer for compression with an elastic dressing, such as an ACE or Coban wrap.
The process of wound healing and scar remodeling is a protracted process. Patients are taught a series of range of motion of exercises in an effort to maximize functional recovery. In serious burns that cross joints, the patient will need to perform therapy on a daily basis to maintain range of motion and preserve function. These patients require evaluation in the postoperative period by a therapist experienced in care of the burned victim. In an effort to reduce hypertrophic scarring, most burn centers use custom-fitted pressure garments.
TAKE HOME POINTS
· The presence of smoke inhalation is a greater predictor of mortality than the age of the patient and the size of the burns.
· Circumferential burns of the chest wall can decrease pulmonary compliance producing respiratory embarrassment.
· Burn excision of 20% can result in the loss of a total blood volume.
· The maximal area of excision that should be performed in one operation is 20% TBSA or a maximal operating time of 2 hours.
· Burn resuscitation with normal saline can produce a hyperchloremic metabolic acidosis.
· Carbon Monoxide is the leading cause of poisoning deaths in the United States.
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