Burn Injury

Burns in MWDs are typically caused by structure fires, motor vehicle mufflers, scalding liquids (i.e., boiling water, frying oil, etc.), caustic chemicals or explosions. While uncommon, these injuries can cause not only severe pain and complicated local wounds but also result in serious metabolic abnormalities and systemic infection that can lead to life-threatening compromise.

BURN CLASSIFICATION IN MWDS5-7

Burns affecting dogs are physically similar to those in humans. Carefully clip over burned areas for adequate assessment. Be sure to evaluate the paw pads for burns, evident by depigmentation of pads, pads appearing grossly hyperemic and swollen, loss of hair adjacent to pads, exudation, lameness, and reluctance to walk.

- Superficial (equivalent to first-degree) burns are red and painful, similar to a sunburn, and involve the outer layer of the epidermis.
- Partial thickness (equivalent to second-degree)
  - Superficial partial thickness burns are red or mottled, with epidermal sloughing, fluid leakage, swelling, extreme hypersensitivity (pain), and involve the epidermis and variable amounts of the dermis. Hair should not easily pull out.
  - Deep partial-thickness burns are black or yellow-white and hair follicles are destroyed. The skin surface is dry. These burns are usually less painful as nerve endings are destroyed. If any hair remains, it will pull out easily.
- Full-thickness (equivalent to third-degree) burns are black, dry, and leathery. These burns have destroyed the epidermis and dermis and expose underlying connective tissue, muscle, and bone. Any eschar that forms is painless.

INHALATION INJURY

Burn patients may have significant inhalation injury that occurs primarily in the pharynx and upper trachea. Perform an oral exam to look for evidence of thermal injuries in the mouth that could indicate thermal injuries lower in the airway. Clinical signs of inhalation and pulmonary injuries may not manifest for several hours, and the full extent may not be observed for 24 to 36 hours. Clinical signs of inhalation injury include stertor or stridor, harsh upper airway sounds, coughing, production of dark sputum, tachypnea, and respiratory distress.

Diagnostics include thoracic radiographs, pulse oximetry, and venous or arterial blood gas analysis. Treatment involves oxygen supplementation in addition to nebulization with sterile saline, chest coupage, and analgesic medications. Observe MWDs with inhalation injuries closely for respiratory distress to assess if orotracheal intubation or (uncommonly) tracheostomy or cricothyrotomy is needed.5

Carbon monoxide (CO) is the most frequent cause of immediate death following smoke inhalation in humans. CO displaces oxygen on red blood cells which can lead to significant tissue hypoxia that is most prevalent in high oxygen demand tissues such as the brain and heart. Hemoglobin bound to oxygen and CO appear the same when measured with pulse oximetry, therefore oxygen saturation measurements (SpO2) will be falsely elevated and as such arterial blood gas CO-oximetry (measuring carboxyhemoglobin) should be utilized to confirm CO toxicity. Additionally, the mucous membranes may appear normal, or may appear bright cherry red, masking tissue hypoxia. Early oxygen therapy is the mainstay treatment for CO toxicity.5

THERMAL OCULAR INJURY

If burns have affected the face and/or eyes of the MWD, reference the K9 Ocular Injuries CPG for additional information regarding examination, diagnosis and treatment of ocular injuries.

ESTIMATION OF TOTAL BODY SURFACE AREA BURNED

Determine the severity of the burn once the MWD has been resuscitated and stabilized. General characteristics of the wound that are important to examine include color, texture, presence or absence of pain, moistness, and extent of swelling, if present.

Estimate the percent of total body surface area (TBSA) burned using a modification of the “Rule of Nines” used for humans.6

Add the estimated percent of burn from each of the following body areas to determine TBSA burned (Figure 1).

Figure 1. Body surface area chart, showing surface areas of individual body parts presented as percentage of TBSA.

The percent TBSA is important in calculating initial fluid requirements, assessing severity, anticipating problems and determining prognosis. Patients with TBSA >20% often have severe metabolic problems (e.g., hypovolemic shock, albumin and electrolyte losses, metabolic acidosis, renal failure) and patients with TBSA >50% have a poor prognosis.7

Prognosis must also consider not only TBSA but also burn severity. Initial evaluation of burn severity may be inaccurate, as wounds progress over a period of 3 to 7 days before completely manifesting ultimate severity.7, 8

GENERAL PATIENT MANAGEMENT RECOMMENDATIONS7-10

Monitor and treat for complications related to burn injury, to include shock, fluid losses, respiratory problems, and electrolyte abnormalities. Manage pain using appropriate analgesics. (See K9 Analgesia and Anesthesia CPG.) Frequent monitoring of vital parameters is essential in severely burned patients. Additional monitoring may include urine output, pain scores, bloodwork (i.e., complete blood count, biochemistry profiles, venous blood gases), pulse oximetry, and blood pressure.

Shock Resuscitation

If burns are greater than 20% TBSA, fluid resuscitation should be initiated as soon as IV (or intraosseous) access is established. Initiate resuscitation with (order of preference) Lactated Ringer’s, Plasma-Lyte A/Normosol-R, or normal saline. Initial fluid rate is calculated as % TBSA burned x 10 mL/hour. If hemorrhagic shock is also present, resuscitation for hemorrhagic shock takes precedence over resuscitation for burn shock. If the wounds are partial or full thickness, hypovolemic shock can also occur from fluid sequestration in the burn area in the first 12 hours

Because the fluid loss can be profound, plasma products should be considered as a part of the continued fluid plan as indicated on an individual patient basis.7

Oxygen Therapy

Humidified oxygen therapy is important to initiate early in resuscitation for every patient with suspected smoke inhalation. CO toxicity can be masked by normal mucous membrane color and a falsely elevated pulse oximetry. The goal of oxygen therapy should be to administer as high of a fraction of inspired oxygen as possible and should be continued for a minimum of five hours if possible.5

Skin Cooling

If the patient presents within two hours of the burns occurring, cool the burned skin using cool water (45-65° F) by immersion, application of compresses, or gentle spray for at least 30 minutes. Cooling is analgesic and improves long-term wound healing with benefits seen if performed within two hours of injury.7,9 Do not apply ice to any burned skin as the vasoconstriction it causes may impede wound healing and may worsen the extent of tissue damage. Measure the patient’s rectal or esophageal temperature frequently to monitor for and prevent hypothermia due to systemic extravasation of fluid and evaporative fluid loss.

Minimize Contamination

- Minimize potential contamination of burned skin and resulting wounds.
- Wash hands thoroughly before handling patients.
- Wear clean exam gloves (superficial burns, superficial partial-thickness burns) or sterile surgical gloves (deep partial-thickness burns, full-thickness burns) for each wound.
- Follow strict aseptic technique when placing invasive devices and use clean examination gloves whenever handling catheters, adapters, fluid lines, etc. Unless necessary, do not place invasive devices through burned skin.

Nursing Care

- Provide excellent nursing care.
- Turn or rotate the MWD every 4 hours if recumbent and perform passive range of motion exercises of all limbs except burned limbs every 4 hours.
- Provide soft, padded bedding.
- Prevent urine scalding and fecal soiling.
- Allow MWDs to eat and drink if able. Major burns cause a hypermetabolic state characterized by hyperglycemia and catabolism of body protein stores. A high-energy critical care diet is recommended.
- Maintain thermoregulation, particularly for burns >20% TBSA, since severe burns lose heat rapidly through denuded skin, making it harder to maintain core body temperature. Recommend keeping denuded areas covered and keeping MWD in a warm relatively humid environment with routine monitoring of rectal temperatures.

SPECIFIC BURN WOUND MANAGEMENT RECOMMENDATIONS4-5,7

- Depending on severity and extent of burn, the patient may require daily heavy sedation or general anesthesia to allow debridement and management. (See K9 Analgesia and Anesthesia CPG.)
- Superficial or superficial partial-thickness burns are generally managed with daily cool water lavage, followed by topical silver sulfadiazine cream application until healed or the wound worsens.
- Deep partial-thickness and full-thickness burns need varying degrees of daily wound debridement (non-surgical or surgical).
- Non-surgical debridement of deep partial-thickness and full-thickness burns involves hydrotherapy using sterile saline lavage and application of a hyperosmotic moisture retentive dressing (e.g., honey, hypertonic saline) under a bandage.
- Surgical debridement is removal of obvious necrotic or dead tissue using aseptic technique and sharp dissection. This may be necessary in very deep or widespread wounds to more aggressively remove necrotic tissue. Following surgical debridement, a moisture retentive dressing (see K9 Wound Management CPG) and bandage is also applied.
- Prophylactic systemic antimicrobials are not routinely administered for managing burns. Provide systemic antibiotic coverage only for MWDs presumed to be immunocompromised, with pneumonia, acute lung injury, or with suspected or confirmed sepsis. Topical antimicrobials such as silver sulfadiazine are preferable to systemic treatment unless other indications justify their use.10
- Bandage burn wounds if the burn area is amenable to application (i.e., the bandage will not increase the potential for wound injury). For large areas that are not able to be bandaged, silver sulfadiazine should be used to cover the burn area and the patient kept in a low-fomite environment (i.e., a clean kennel). Change bandages daily or more often if wound exudate is excessive and/or the bandage becomes soiled.
- Extremity compartment syndrome secondary to burns is rare in dogs; this seems to be a much more common and severe problem in humans. Measures to control intracompartmental pressures like fasciotomy would be rarely needed.