Introduction
Burn injuries are a significant yet often underappreciated form of trauma that can impact anyone, anywhere, at any time. These injuries are commonly caused by heat from hot liquids, solids, or fire but can also result from friction, cold, radiation, chemicals, or electricity. Understanding the various causes, types, epidemiology, mechanisms, pathophysiology, and diagnostic methods for burn injuries is crucial for effective management and recovery.
Causes of Burn Injuries
- Burn injuries can result from multiple sources:
- Thermal Burns: Caused by contact with hot objects, liquids, steam, or fire. Examples include burns from flames, hot grease, or scald injuries from hot liquids or steam.
- Chemical Burns: Result from exposure to acidic or alkaline substances. Alkaline chemicals cause colliquative necrosis, transforming tissue into a liquid mass, whereas acidic burns cause coagulation necrosis, preserving the tissue architecture.
- Electrical Burns: Occur when an electric current passes through the body, causing deep tissue damage that often exceeds the visible skin injury.
- Cold Burns: Also known as frostbite, occur through mechanisms like direct cellular injury from crystallization of water in tissues and indirect injury from ischaemia and reperfusion.
Epidemiology of Burn Injuries
Burn injuries are a global health problem with significant morbidity and mortality:
- Incidence: Approximately 11 million burn injuries occur globally each year, with about 180,000 resulting in death. In the United States, more than 450,000 individuals receive medical treatment for burn injuries annually, with 40,000 requiring hospitalization and over 60% being treated at specialized burn centers.
- Demographics: Nearly 70% of burn victims are male, with the highest risk between ages 18 and 35. Children under 5 years old are particularly vulnerable to scald injuries, accounting for 43% of scald-related burns. Elderly patients have a disproportionately higher death rate from burn injuries.
- Risk Factors: Risk factors include children under 4 years of age, adults over 65 years, African Americans, Native Americans, people living in rural areas, those in manufactured or substandard housing, and individuals living in poverty.
Mechanisms of Burn Injuries
The mechanisms behind burn injuries involve various physical and chemical processes:
- Heat Transfer: Burns occur when energy from a heat source is transferred to the skin and underlying tissues. This transfer can be rapid and intense, as with flames or hot grease, or slower and less severe, as with scalds from hot liquids.
- Chemical Reactions: Chemical burns result from the reaction between the skin and corrosive substances. Alkaline substances penetrate deeper and cause liquefactive necrosis, while acids typically cause coagulative necrosis.
- Electrical Current: Electrical burns are caused by the passage of electrical current through the body, leading to deep tissue damage and potential cardiac and neurological complications.
- Cold Exposure: Cold burns or frostbite result from prolonged exposure to freezing temperatures, causing ice crystal formation in tissues and subsequent cell damage.
Pathophysiology of Burn Injuries
The pathophysiology of burn injuries involves complex physiological and pathophysiological responses that vary depending on the cause and severity of the burn:
1. Zones of Injury: Immediately after a burn injury, the burn wound can be divided into three zones:
- Zone of Coagulation: The central area with the most damage, where cells are irreversibly damaged.
- Zone of Stasis: Surrounding the zone of coagulation, characterized by decreased perfusion and potentially salvageable tissue.
- Zone of Hyperaemia: The outermost area with increased blood flow and minimal cell injury.
2. Inflammatory Response: The initial inflammatory response involves the release of cytokines and other inflammatory mediators, leading to increased vascular permeability, fluid loss, and tissue edema. This response can be beneficial for wound healing but may become excessive in severe burns, leading to systemic inflammatory response syndrome (SIRS).
3. Hypermetabolic State: Severe burns trigger a hypermetabolic state characterized by increased energy expenditure, protein catabolism, and muscle wasting. This state can persist for months or even years after the injury, complicating recovery and increasing the risk of complications such as infections and organ failure.
4. Immune Dysregulation: Burn injuries compromise the immune system, making patients more susceptible to infections. This immune dysfunction is caused by both the direct effects of the burn and the systemic inflammatory response, which can lead to immune suppression.
5. Systemic Effects: Severe burns can cause systemic effects such as hypovolemic shock, due to massive fluid loss, and distributive shock, caused by widespread vasodilation. This can result in decreased cardiac output, reduced organ perfusion, and multi-organ failure.
Types of Burn Injuries
Burns are classified based on their severity and the depth of tissue damage:
1. First-Degree Burns: Affect only the outer layer of skin (epidermis). These burns are red, painful, and typically heal without scarring.
2. Second-Degree Burns: Involve the epidermis and part of the dermis. They are further categorized into:
- Superficial Partial-Thickness Burns: Painful, blister, and may scar but usually heal without surgery.
- Deep Partial-Thickness Burns: Less painful due to nerve damage, require surgery, and will scar.
3. Third-Degree Burns: Extend through the full dermis, are not typically painful due to nerve damage, and require surgical management to prevent infection.
4. Fourth-Degree Burns: Affect deeper tissues such as muscle or bone, often leading to loss of the burned part.
Diagnosis of Burn Injuries
Accurate diagnosis and assessment of burn injuries are essential for effective treatment and management. The diagnostic process involves:
- Primary Survey: Initial assessment at the scene or emergency department focusing on airway, breathing, circulation, and disability. This includes evaluating the extent of the burn using tools like the Rule of Nines for adults and the Lund and Browder chart for children.
- Secondary Survey: A thorough examination to identify the depth and size of the burn, associated injuries, and potential complications. This includes laboratory tests (e.g., complete blood count, electrolytes, coagulation profile) and imaging studies as needed.
- Burn Depth Assessment: Determining the depth of the burn is critical. This can be challenging but involves clinical examination and may utilize advanced imaging techniques like laser Doppler imaging, harmonic ultrasound, and optical coherence tomography to enhance accuracy.
First Aid for Burn Injuries
Immediate and appropriate first aid can significantly impact the outcome of a burn injury:
- Stop the Burning Process: Remove the source of the burn or move the patient away from the source. Extinguish flames by rolling the patient on the ground, covering them with a blanket, or using water.
- Cool the Burn: Apply cool (not cold) running water to the burn for at least 10-20 minutes to reduce pain and heat. Avoid using ice, as it can cause further tissue damage.
- Protect the Burn Area: Cover the burn with a clean, non-stick bandage or cloth to protect it from contamination and reduce pain.
- Remove Constrictive Items: Remove jewelry, belts, and tight clothing near the burn area before swelling begins.
- Seek Medical Attention: For severe burns, chemical burns, electrical burns, or burns involving the face, hands, feet, genitals, or major joints, seek immediate medical attention.
Rule of Nines
The Rule of Nines is a quick method used to estimate the total body surface area (TBSA) affected by a burn. It divides the body into sections, each representing approximately 9% (or multiples of 9%) of the TBSA:
- Head and neck: 9%
- Each arm: 9%
- Each leg: 18%
- Anterior trunk: 18%
- Posterior trunk: 18%
- Perineum: 1%
This method is particularly useful for adults. For children, the Lund and Browder chart provides a more accurate estimation, accounting for differences in body proportions.
Inhalation Injury
Inhalation injuries occur when smoke, hot air, steam, or toxic fumes are inhaled during a fire. These injuries can significantly increase the morbidity and mortality associated with burns.
Types of Inhalation Injury
- Upper Airway Injury: Caused by direct heat and chemicals, leading to swelling, obstruction, and difficulty breathing.
- Lower Airway Injury: Results from inhalation of chemicals and particulates, causing inflammation, bronchospasm, and potentially acute respiratory distress syndrome (ARDS).
- Systemic Toxicity: Inhalation of toxic gases like carbon monoxide and cyanide can lead to systemic poisoning.
Symptoms of Inhalation Injury
- Hoarseness, stridor, or wheezing
- Burns around the mouth or nose
- Soot in the nasal passages or sputum
- Difficulty breathing or respiratory distress
- Signs of carbon monoxide poisoning (e.g., headache, dizziness, confusion)
Diagnosis and Management
- Initial Assessment: Evaluate the airway, breathing, and circulation. Look for signs of inhalation injury.
- Airway Management: Early intubation may be necessary to secure the airway and prevent obstruction due to swelling.
- Oxygen Therapy: Administer 100% oxygen to treat hypoxia and carbon monoxide poisoning.
- Bronchoscopy: Used to assess the extent of airway injury and guide treatment.
- Supportive Care: Includes mechanical ventilation, bronchodilators, and humidified oxygen to manage respiratory symptoms.
Conclusion
By understanding the causes, epidemiology, mechanisms, pathophysiology, types, diagnostic methods, and first aid for burn injuries, individuals and healthcare providers can be better prepared to manage such incidents effectively and promote faster recovery and healing.
In the next part, we will delve into the detailed management approaches for burn injuries, including wound management, fluid resuscitation, and rehabilitation. Stay tuned for comprehensive insights into how to handle burn injuries and support recovery.
References
- Jeschke, Marc G., et al. “Burn injury.” Nature Reviews Disease Primers 6.1 (2020): 11.
- Tintinalli, Judith E., et al. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 9th ed., McGraw-Hill Education, 2020, pp. 1412-1435.
