Burn Injuries: Pathophysiology, Assessment, and Management
1. Introduction to Burns and Their Impact
Burns are serious soft-tissue injuries resulting from the transfer of destructive energy, primarily thermal, electrical, or radiation, with temperatures exceeding 44ºC causing tissue damage. The severity of a burn directly correlates with the amount of heat energy and duration of exposure. Fire-related deaths are a significant concern, with "82% of occupant deaths occur in residential constructions." Canada experiences approximately 1,000 fire-related deaths annually.
2. Anatomy and Function of the Skin
The skin, also known as the integument, serves several vital functions:
• Protection: Acts as a barrier against external threats.
• Temperature Regulation: Helps maintain body temperature.
• Water Regulation: Prevents excessive water loss.
• Sensory Reception: Contains nerve endings for touch, pain, and temperature.
Burns directly impact these functions. The skin comprises three main layers:
• Epidermis: The outermost layer.
• Dermis: Contains nerve endings, cutaneous blood vessels, sweat glands, hair follicles, and sebaceous glands.
• Subcutaneous layer: Composed of adipose (fat) tissue.
The eyes are particularly vulnerable to burn injuries, with tear ducts and eyelids providing lubrication.
3. Types of Burns and Associated Pathophysiology
Burns can be categorized by their source of energy and the specific physiological effects they induce:
3.1. Thermal Burns
Caused by heat energy, including:
• Flame burns
• Scald burns (hot liquids)
• Contact burns (direct contact with hot objects)
• Steam burns
• Flash burns
3.2. Burn Shock
A systemic response to severe burns involving both absolute and relative fluid loss, leading to:
• Hypovolemic shock: Actual loss of fluid volume.
• Distributive shock: Fluid shifts within the body, affecting the entire system. Fluid replacement is crucial, and the onset of burn shock often takes "6 to 8 hours."
3.3. Inhalation Injuries (Thermal and Smoke)
These are critical complications of fires:
• Thermal Inhalation Burns: Direct heat damage to the airway tissue, which can cause "rapid and serious airway compromise." Swelling, particularly in the upper airway (supraglottic), can completely obstruct the airway and be fatal.
• Smoke Inhalation: The majority of fire-related deaths are due to "inhalation of toxic gases," upper airway compromise, and pulmonary injury. Smoke contains numerous toxic chemicals, leading to thermal burns, hypoxia (from lack of oxygen), and tissue damage.
3.4. Carbon Monoxide (CO) Intoxication
CO is a product of almost all forms of combustion. It is highly dangerous because "CO binds to receptor sites on hemoglobin at least 250 times more easily than oxygen," displacing oxygen and leading to hypoxia. It should be suspected when multiple individuals in the same location report headaches or nausea. "Do not expect a 'cherry red' appearance" as a reliable sign.
3.5. Chemical Burns
Caused by various corrosive materials, including:
• Acids
• Alkalis or bases
• Oxidizing agents
• Phosphorous
• Vesicants Mechanisms of damage include reduction, oxidation, corrosion, protoplasmic poisons, desecration, and vesication. Chemical burns to the eye require immediate and copious flushing with water; "Never use antidotes in the eyes—irrigate with water only."
3.6. Electrical Burns
These are often classified as major burns and include:
• Contact burns: The most common type.
• Flash burns: Electrothermal injury.
• Flame burns: Thermal injury secondary to electrical current. Electrical burns can cause significant internal damage beyond visible surface wounds. "Alternating current (AC) is considerably more dangerous than direct current (DC); it can freeze the victim to the conductor." Non-burn injuries associated with electricity include asphyxia, cardiac arrest, neurologic complications, kidney damage, and muscle spasms leading to fractures.
3.7. TASER Effects
While typically resulting in minor injuries (soft-tissue injury, bleeding, infection) from the deployed electrodes, TASER devices incapacitate via electromuscular disruption and may necessitate emergency medical care.
3.8. Lightning Injuries
Lightning carries immense electrical power (100 million volts / 200,000 amps). Most victims are not struck directly. Prevention is key (avoid being the tallest conductor, seek substantial shelter). Management is similar to high-voltage line injuries, with aggressive CPR for cardiac arrest victims.
3.9. Radiation Burns
Caused by ionizing radiation (alpha, beta, gamma). Severity is measured in rad, rem, or gray (Gy). Radiation can cause "Acute radiation syndrome" affecting hematologic, central nervous system, and gastrointestinal systems, as well as contact burns. Scene safety and contacting hazardous materials teams are paramount for radiation burn incidents.
4. General Assessment of Burns
The assessment of burn injuries is challenging, as the full extent of injury may not be immediately apparent.
• Scene Safety: Always the primary concern. For recent burns, extinguish flames, cool the burn, and remove smoldering clothing.
• Initial Assessment: Evaluate mental status, ensure an open airway (early intubation may be critical), assess breathing (provide humidified oxygen), and ensure adequate circulation (burn shock can develop slowly).
• Severity Assessment:
◦ Burn Depth: Superficial burn: Epidermis only, red, painful (e.g., sunburn). Partial-thickness burn: Epidermis and dermis. Superficial: Red, blisters/moisture, painful, heals spontaneously but may scar. Deep: Extends into dermis, very painful, often caused by hot liquids/steam/grease. * Full-thickness burn: All skin layers destroyed, white/pale/brown/leathery/charred, no pain sensation, usually requires skin grafting.
◦ Surface Area Involved (Total Body Surface Area - TBSA): Rule of Nines: Divides the body into sections, mostly 9% each (genitalia 1%). Varies for infants and small children. Rule of Palms: Patient's palm is approximately 1% TBSA, useful for smaller or irregularly shaped burns. * Lund and Browder Chart: Provides more specific regional divisions for accuracy.
• Focused History and Physical Examination: Check for other injuries, cover injured eyes, assess for circumferential burns, obtain a brief history, and perform a detailed physical examination en route to the emergency department.
5. Management of Burns
The management of burns involves four phases, with EMS primarily involved in the first.
5.1. General Management Principles
• Stop the burning!
• Cool with water for several minutes (except for specific chemical burns).
• Keep the patient warm to prevent hypothermia (do not cool the entire body for superficial burns).
• Treat other injuries.
• "Do not use salves, ointments, creams, sprays, or any similar materials on any type of burn."
5.2. Airway Management
Airway compromise is a critical concern, especially with inhalation injuries.
• Acutely decompensating airway: Requires immediate prehospital intubation (e.g., cardiac/respiratory arrest, rapidly increasing swelling). Surgical airway may be needed if intubation fails.
• Deteriorating airway (burns/toxic inhalations): Best deferred to the hospital; rapid sequence intubation is difficult.
• Patent airway with risk factors: Administer humidified oxygen, do NOT intubate, but notify the hospital.
• No signs/risk factors: Normal oxygen, no intubation needed.
5.3. Fluid Resuscitation
• Patients with burns covering "more than 20% of the TBSA will need fluid resuscitation."
• Establish large-bore IV early; do NOT delay transport.
• Use lactated Ringer solution or normal saline, avoiding burned areas if possible (but use burned upper extremity over lower if necessary).
• Consensus Formula (Parkland formula):
◦ Fluid needed in first 24 hours: 2 to 4 mL solution × body weight (in kg) × percentage of body surface burned.
◦ Half of this fluid is given in the first 8 hours, the second half over the next 16 hours.
5.4. Pain Management
• "Aggressive pain management is appropriate."
• Reassess pain every 5 minutes. Burn patients may require higher than expected doses. Follow protocols.
5.5. Specific Burn Type Management
• Superficial Burns: Cool well to stop burning and relieve pain. No further prehospital treatment typically needed.
• Partial-Thickness Burns: Cool, elevate burned extremities, do NOT rupture blisters, establish IV fluids, consider pain management.
• Full-Thickness Burns: Pain assessment and management. Usually, dry dressings are used after the fire is out.
• Chemical Burns: "Speed is essential." Immediately flush exposed areas with copious water and remove clothing. Avoid self-exposure. Do not waste time seeking antidotes. Special cases (e.g., dry lime brushed off, sodium metals coated with oil, hydrofluoric acid with calcium chloride jelly). For eye burns, flush with large quantities of water and remove contacts; never use antidotes.
• Electrical Burns: Scene safety is paramount (ensure power is off). Open airway, CPR, monitor for ventricular fibrillation. Look for entrance and exit wounds (majority of damage internal). Early oxygen and shock management.
• Lightning-Related Injury: Move victims to a safe area (multiple victims may be present). Aggressive, continuous CPR for cardiac arrest.
• Radiation Burns: Scene safety, contact hazardous materials team. Irrigate open wounds gently. Decontaminate contact radiation burns like chemical burns.
6. Special Considerations for Pediatric and Geriatric Patients
6.1. Pediatric Burn Patients
• "More than one-half of fire-related deaths and injuries in children involve preschoolers." They are less effectively awakened by smoke detectors.
• "Young children’s thin skin and delicate respiratory structures are more easily damaged by thermal insults."
• Fluid resuscitation is more challenging due to their increased body surface-to-weight ratio, potentially requiring "more fluid per kilogram than adults."
6.2. Geriatric Burn Patients
• "170 older adults die of fire-related causes each year in Canada," with smoking being a leading cause.
• "Particularly sensitive to respiratory insults."
• Have poor glycogen stores, requiring blood glucose level checks for hypoglycemia.
• Cardiac monitoring should be implemented, and be alert for pulmonary edema.
7. Burn Centre Criteria
Patients meeting any of the following criteria should be transferred to a specialized burn center:
• Partial-thickness burns > 10% TBSA.
• Burns of face, hands, feet, genitalia, perineum, or major joints.
• Any full-thickness burns.
• Any electrical burns (including lightning).
• All chemical burns.
• All inhalation burns.
• Burns complicated by pre-existing medical conditions or other traumatic injuries.
• Burns to children in hospitals without qualified personnel or equipment.
• Burns requiring special rehabilitation.
8. Long-Term Consequences
Serious burns are "life-changing events." Patients may require extensive rehabilitation, facing challenges with thermoregulation, motor function, and sensory function. Survival rates are currently higher than ever. For paramedics, responding to fire scenes is "one of the most horrifying tasks," and their initial actions have a long-term impact on patient outcomes.