Understanding Burns and Skin Function

Burns

• Burns are injuries to skin or other organic tissue, primarily caused by heat, radiation, electricity, chemicals, friction, or contact with chemicals
• Thermal burns occur when cells in the skin or other tissues are destroyed by hot liquids (scalds), hot solids (contact burns), or flames (flame burns)
• Burns are classified into two groups based on tissue damage: superficial partial-thickness burns and full-thickness burns

Learning Objectives

• Discuss different types of burns
• Link skin function to maintaining homeostasis during burns
• Apply pathophysiology during burns
• Discuss clinical assessments of burns
• Discuss clinical management to correct pathophysiology

Skin and Homeostasis

• Skin is the largest organ system in the body
• Epidermis has five layers
• Dermis has two layers
• Deepest layers of epidermis regenerate every 2-3 weeks
• Epidermis requires dermal tissue to regenerate

Classification of Burns

• Burns are classified by depth of burn and layers of skin affected
• Superficial epidermal burns: affects epidermis only, skin is red and painful, no blisters, capillary refill quickly
• Superficial dermal (partial thickness) burns: involves epidermis and upper layers of dermis, skin is often reddish-pink, painful, blistering; capillary refill slow to return to normal
• Deep dermal (partial thickness) burns: epidermis and upper/deeper layers of dermis are involved, skin typically appears dry, blotchy, or mottled; capillary refill is slow or doesn't return
• Full thickness burns: extends through all layers of skin, possibly into muscle or bone; skin color is white or black, waxy or leathery, and painless with loss of sensation

Pathophysiology: Local Response

• Burns involve three zones: coagulation, stasis, and hyperemia
• Zone of coagulation: maximal damage; cell death, protein denaturation, and damaged circulation; irreversible tissue loss
• Zone of stasis: potentially salvageable tissue; aiming to increase tissue perfusion; can become irreversible with infection and hypotension
• Zone of hyperemia: increased blood flow due to inflammation; will recover unless it becomes systemic infections like sepsis

Pathophysiology: Systemic Response

• Release of cytokines and inflammatory mediators at the burn site creates systemic effects once the burn area reaches 30% of total body surface area.
• Cardiovascular changes: fluid leaks from vessels, leading to loss of intravascular proteins and fluid; peripheral and splanchnic vasoconstriction; reduced cardiac contractility, hence increased heart rate and oxygen consumption; this results in systemic hypotension and end-organ hypoperfusion.
• Respiratory changes: inflammatory mediators cause bronchoconstriction and decreased perfusion; severe burns can lead to adult respiratory distress syndrome (ARDS), decreased oxygen into blood and carbon dioxide out of blood thus affecting oxygen carrying capacity
• Metabolic changes: threefold increase in metabolic demands causing muscle, bone, and adipose catabolism; insulin resistance; increase in glucose production; decrease in glucose uptake and clearance causing hyperglycemia

Clinical Management - Airway

• Assess patient consciousness; assess for stridor, hoarseness, or wheezing
• Determine if intubation is necessary (assess ventilator, airway equipment, oxygen availability, monitoring, CO2 line, and capnography)
• Smaller tubes may be needed due to swelling/edema

Clinical Management - Breathing

• Assess resistance to breathing: inflammatory mediators cause bronchoconstriction and difficulty breathing
• Assess compliance in lungs and posture: how much the lungs expand and if the burns affect the chest and back; posture may affect short breaths,
• Anaerobic respiration (low oxygen): can lead to lactic acid release, becoming acidotic.

Clinical Management - Surgical Instruments

• Zimmer dermatome
• Watson knife

Clinical Management - Fasciotomy & Escharotomy

• Fasciotomy: incision through fascia to relieve compartment syndrome
• Escharotomy: incision through eschar to restore blood flow

Clinical Management - Circulation

• Fluid loss from vascular permeability: fluid extra uptake on local sites
• Calculate crystalloid (lactated ringers/Hartmans/saline) resuscitation using Parkland formula
• Increase stroke volume to maintain blood pressure (BP)
• Increase oxygen-carrying capacity

Clinical Management - Disability/Conscious Level

• Decreased/altered level of consciousness and brain oxygenation: due to reduced oxygen reaching the brain due to increased body demands and may require intubation for controlled ventilation
• Evaluate and correct hypoxia and hypercapnia

Clinical Management - Exposure

• Document full extent of injuries, calculations for different burn types are often done in burn units

Skin Grafts

• Allograft: from cadaver or living donor; lasts 2-4 weeks, can be xenograft (different species)
• Autograft: from patient's own skin (split skin or full thickness); meshed grafts are possible using paraffin oil or saline

Application to Practice

• Theatre temperature >29°C
• Warm IV fluids
• Correct airway and positioning
• Consider pressure area management
• Manage drugs and infusions
• Control movement to reduce infection
• Early excision and immediate grafting improve survival rates
• Development of grafts, working with grafts, and infection control improve survival rates

Case Study

• 20-year-old female with 3rd-degree burns to face, chest, and arms.
• Presented with respiratory issues (cyanosis, swollen lips and tongue, RR 30, SpO2 decreased, wheeze, crackles)
• Unstable vital signs (HR 150, BP 103/62, unrecordable temperature) and unable to measure central BP
• Glucose levels of 7.5 mmol/l, full thickness burns, and other considerations (AVPU, abnormal posture)