Feline Burns Study Guide

Overview and Clinical Importance

Burns are injuries to the skin and underlying tissues caused by thermal, chemical, electrical, or mechanical energy sources. In cats, burns represent a significant emergency condition requiring immediate assessment and treatment. The curious nature of cats predisposes them to specific burn scenarios including stovetop contact, electrical cord chewing, and exposure to caustic household chemicals.

Understanding burn classification, pathophysiology, and management is essential for the NAVLE, as questions frequently address initial stabilization, fluid resuscitation calculations, wound care protocols, and prognosis determination based on burn severity and extent.

Etiology and Types of Burns

Burns in cats are classified by their causative mechanism, each with unique clinical considerations and management requirements.

Thermal Burns

Thermal burns are the most common type in cats and result from contact with excessive heat. Common sources include stovetop burners (most frequently affecting paw pads), electric heating pads used during anesthesia recovery, hot liquids (scalding), radiators, heat lamps, fires, and automobile engine compartments where cats may seek warmth.

The severity depends on both temperature and duration of contact. Temperatures above 44°C (111°F) cause cellular injury, with damage severity increasing exponentially with temperature elevation.

Chemical Burns

Chemical burns occur when the skin contacts caustic substances. Common agents include acids, alkalis (lye, drain cleaners), household cleaners, gasoline, paint thinners, and pesticides. Alkali burns tend to be more severe than acid burns because they cause liquefaction necrosis, allowing deeper tissue penetration, whereas acids cause coagulation necrosis that limits penetration depth.

Cats may also suffer chemical burns to the oral cavity and tongue during grooming attempts to remove the substance from their fur. Chemical fumes can additionally cause respiratory tract burns.

Electrical Burns

Electrical burns most commonly occur when cats, particularly kittens, chew on electrical cords. The injury results from electrical current converting to thermal energy at the point of tissue contact. Burns typically affect the lips, tongue, palate, and teeth. Moist oral mucosa provides minimal resistance to electrical current, allowing deeper tissue damage.

Mechanical Burns

Mechanical burns (friction burns) result from repetitive friction against the skin, such as from rope or carpet. These are less common in cats than other burn types but may occur during trauma or escape attempts.

Burn Classification by Depth

Burns are classified according to the depth of tissue damage, which determines treatment approach and prognosis. The full extent of burn wounds may take up to 3 days to declare, as thermal energy dissipates slowly through tissues.

Estimating Burn Extent: Rule of Nines

The total body surface area (TBSA) affected by burns is estimated using the adapted veterinary Rule of Nines. This estimation guides fluid resuscitation and prognosis.

Burn Severity by TBSA:

• Local burns: Less than 20% TBSA - generally manageable with wound care
• Severe burns: Greater than 20% TBSA - systemic complications likely, intensive care required
• Critical burns: Greater than 50% TBSA - guarded to grave prognosis, prolonged intensive care

Pathophysiology of Burns

Jackson's Burn Model: Three Zones of Injury

Burn wounds consist of three concentric zones with different treatment implications:

• Zone of Coagulation: Central area of irreversible necrosis nearest the heat source with complete protein denaturation
• Zone of Stasis: Intermediate zone with compromised perfusion; cellular damage is potentially reversible. This zone is the target of resuscitation efforts. Without intervention, tissue may progress to necrosis (burn wound conversion) within 24-48 hours
• Zone of Hyperemia: Outermost zone with vasodilation and increased blood flow; minimal cellular damage, typically recovers fully

Systemic Effects of Severe Burns

Burns affecting greater than 20% TBSA trigger systemic inflammatory response with multiple organ effects:

• Cardiovascular: Increased capillary permeability leads to massive fluid shifts from intravascular to interstitial space (third-spacing), causing hypovolemic shock, decreased cardiac output, and hypotension
• Metabolic: Hypermetabolic state with protein catabolism, negative nitrogen balance, insulin resistance (burn diabetes), and increased energy requirements (up to 2-3x normal)
• Immune: Immunosuppression with impaired cell-mediated immunity, decreased neutrophil function, and compromised humoral response increasing infection risk
• Protein: Hypoproteinemia from protein loss through wounds and increased catabolism; may require plasma or albumin supplementation
• Electrolyte: Hyperkalemia (early, from cellular destruction), followed by hypokalemia; sodium and acid-base abnormalities common

Emergency Management

Initial Assessment and Stabilization

Apply standard trauma protocols with attention to burn-specific concerns:

• Safety: Remove patient from heat source; ensure electrical source is disconnected before touching electrically burned patient
• Airway: Assess for smoke inhalation or oropharyngeal burns; singed whiskers/nasal hair suggest inhalation injury
• Breathing: Provide supplemental oxygen; monitor for delayed pulmonary edema especially with electrical burns
• Circulation: Establish IV access (through unburned skin if possible); begin fluid resuscitation for burns greater than 15-20% TBSA

Initial Wound Cooling

For thermal burns presenting within 2-3 hours of injury:

• Apply cool (not cold) running water at 15-25°C for 10-20 minutes
• Chilled sterile saline can be applied to wound
• Cooling is analgesic, reduces edema, and may limit zone of stasis progression

Fluid Resuscitation

Aggressive fluid resuscitation is critical for burns affecting greater than 15-20% TBSA to prevent hypovolemic shock and maintain organ perfusion.

Parkland Formula with Feline Modification

The standard Parkland formula calculates total crystalloid volume for the first 24 hours:

Administration Schedule:

• First 50% of calculated volume: Administer over the first 8 hours (from time of burn, not admission)
• Remaining 50%: Administer over the subsequent 16 hours
• Preferred fluid: Lactated Ringer's solution (LRS)
• Avoid glucose-containing fluids initially (risk of hyperglycemia)

Monitoring Adequacy of Resuscitation:

• Target urine output: 1-2 mL/kg/hr (place urinary catheter for accurate monitoring)
• Heart rate, blood pressure, capillary refill time
• Central venous pressure (if available)
• Serial lactate measurements

Electrical Burns: Special Considerations

Electrical injuries in cats predominantly occur from cord chewing in young, curious cats. These injuries require specific management considerations beyond typical thermal burns.

Clinical Presentation

• Oral burns: Gray/tan lesions on lips, tongue, hard palate, gingiva
• Singed whiskers and facial hair
• Drooling, difficulty swallowing, reluctance to eat
• History of collapse, seizures, or muscle tremors immediately after injury
• Respiratory distress (may be immediate or delayed up to 36 hours)

Noncardiogenic Pulmonary Edema (NCPE)

NCPE is a life-threatening complication occurring in 15-40% of electrically injured animals. It develops secondary to massive catecholamine release causing pulmonary capillary damage and increased permeability.

• Onset: 1-36 hours post-injury (typically peaks at 24-48 hours)
• Clinical signs: Tachypnea, dyspnea, orthopnea, cyanosis, pulmonary crackles, pink frothy fluid from nose
• Diagnosis: Thoracic radiographs show diffuse interstitial to alveolar pattern
• Treatment: Oxygen supplementation, cage rest, judicious IV fluids (avoid overload), consider diuretics cautiously

Oral Burn Management

• Oral antiseptic rinses (chlorhexidine 0.05%)
• Sucralfate suspension to coat esophageal and oral lesions
• Soft food or gruel diet for 2 weeks during healing
• Feeding tube placement if unable to eat due to severe oral burns
• Expected healing time: approximately 2 weeks for oral burns

Wound Management

Initial Wound Care

• Clip and Clean: Liberally clip hair around the wound; thick coats may hide more extensive injury. Lavage with sterile isotonic saline or dilute chlorhexidine (0.05%)
• Allow Wounds to Declare: Full extent may take 3 days to become apparent; avoid aggressive debridement initially
• Cover: Apply non-adherent sterile dressing to protect wound and reduce pain

Topical Antimicrobial Therapy

Debridement

Dead tissue (eschar) must be removed to prevent infection and allow healing. Multiple debridement sessions are often required:

• Sharp/Surgical Debridement: Tangential excision in thin layers until viable bleeding tissue reached (requires anesthesia)
• Autolytic Debridement: Moisture-retentive dressings allow WBCs to perform natural tissue breakdown
• Enzymatic Debridement: Proteolytic enzyme products to liquefy necrotic tissue (slow but less painful)

Bandaging Principles

• Primary layer: Non-adherent contact dressing with topical agent
• Secondary layer: Absorbent padding (rolled cotton, cast padding)
• Tertiary layer: Conforming gauze roll
• Quaternary layer: Self-adherent bandage (CoFlex) or tape
• Bandage changes: Daily initially, then every 2-3 days as wound matures

Analgesia and Supportive Care

Pain Management

Burns are extremely painful; multimodal analgesia is essential:

Nutritional Support

Burn patients have dramatically increased metabolic demands (up to 2-3x normal caloric requirements):

• Early enteral nutrition preferred over parenteral
• High-protein diet to support wound healing and offset catabolism
• Consider feeding tube (esophagostomy, gastrostomy) for facial burns or anorexic patients
• Monitor hydration status by skin turgor and gum moisture

Antibiotics

Systemic antibiotics are not routinely indicated for superficial burns but should be considered for:

• Full-thickness burns
• Signs of wound infection (increasing pain, erythema, purulence, fever)
• Burns greater than 20% TBSA (immunocompromised state)
• Culture and sensitivity testing recommended for infected wounds
• Common topical agents: Gentamicin, polymyxin, neomycin, fluoroquinolones

Prognosis

B - Body surface area (Rule of Nines) U - Urine output (target 1-2 mL/kg/hr) R - Resuscitate fluids (Parkland formula, reduce 25-50% for cats) N - Nutrition (increased metabolic demands) S - Silver sulfadiazine (topical antimicrobial of choice)