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Pathophysiology of Burns


PATHOPHYSIOLOGY OF BURNS Dr. Shiara Ortiz-Pujols Burn Fellow NC Jaycee Burn Center – PowerPoint PPT presentation

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Title: Pathophysiology of Burns

Pathophysiology of Burns
  • Dr. Shiara Ortiz-Pujols
  • Burn Fellow
  • NC Jaycee Burn Center

  • PART 1
  • Anatomy Overview
  • Causes of Burns
  • Estimating Burns (Depth )
  • Categories Zones
  • PART 2
  • Physiologic Implications
  • Pathophysiology
  • Resuscitation
  • Post-Resuscitation
  • Board Questions

  • Adult skin surface 1.5-2.0 m2 (0.2-0.3 in
    newborns) largest organ
  • Skin thickness 1-2 mm peaks age 30-40 Mgt F
  • Functions include
  • protection from external environment
  • maintenance of fluid/electrolyte homeostasis
  • Thermoregulation
  • immunologic function
  • sensation
  • Metabolic organ (i.e., Vit D synthesis)

Causes of Burns
  • Usually caused by heat, electricity, chemicals,
    radiation, and friction
  • Thermal burns are caused by steam, fire, hot
    objects or hot liquids.
  • Most common burns for children and the elderly
  • Electrical burns are the result of direct contact
    with electricity or lightning
  • Chemical burns occur when the skin comes in
    contact with household or industrial chemicals
  • Radiation burns are caused by over-exposure to
    the sun, tanning booths, sun lamps, X-rays or
    radiation from cancer treatments
  • Friction burns occur when skin rubs against a
    hard surface, e.g. carpet, gym floor, concrete or
    a treadmill

Effect of Heat
  • Temporal and quantitative
  • 40-44C, enzymes malfunction, proteins denature
    and pumps fail
  • gt 44C, damage occurs faster than repair
    mechanisms can keep up with
  • Damage continues even when the source is

Effect of Electricity
  • Effects of current depend on several factors
  • - Type of circuit
  • - Voltage
  • - Resistance of body
  • - Amperage
  • - Pathway of current
  • - Duration of contact
  • High voltage (gt1000V) causes underlying tissue
    damage. Deep tissues act as insulators and
    continue to be injured.
  • Resistance of various tissues from L?H nerve,
    vessels, muscle, skin, tendon, fat, bone
  • Ohms Law- VIR
  • Damage more related to cross-sectional area
    which explains extremity injuries without trunk

Electrical Storms/Lightning
  • Burns are characteristically superficial and
    present as a spidery or arborescent pattern.
  • Cardiopulmonary arrest is common following
    lightning injury.
  • Coma and neurologic defects are also common but
    usually clear in a few hours or days.
  • Watch for tympanic membrane rupture
  • Usually lethal in 1/3 of patients.
  • World record for surviving lightning strikes is
    Roy C. Sullivan who was a park ranger from VA.
    Roy was struck 7 times from 1942-1977.

Electrical Pruning
Effect of Chemicals
  • Acids and alkalis cause injury via different
  • Petroleum products can cause delipidation and ?
    depth of wound 2 tendency to adhere to skin
  • Acids
  • coagulation necrosis
  • denaturing proteins upon tissue contact
  • area of coagulation is formed and limits
    extension of injury
  • exception is hydrofluoric acid, which produces a
    liquefaction necrosis similar to alkalis.
  • Acid damaged skin can look tanned and smooth do
    not mistake for a suntan.
  • Alkalis
  • liquefaction necrosis
  • potentially more dangerous than acid burns
  • liquefy tissue by denaturation of proteins and
    saponification of fats
  • In contrast to acids, whose tissue penetration is
    limited by the formation of a coagulum, alkalis
    can continue to penetrate very deeply into tissue
  • Can cause severe precipitous airway edema or

Inhalation Injury
  • Heat dispersed in upper airways leads to edema
  • Cooled smoke and toxins carried distally
  • Increased blood flow to bronchial arteries causes
  • Increased lung neutrophils mediators of lung
    damage release proteases and oxygen free
    radicals (ROS)
  • Exudate in upper airways formation of fibrin

Stages of Inhalation Injury
  • Stage 1 acute pulmonary insufficiency
  • Signs of pulmonary failure at presentation
  • Stage 2 72-96 hrs after presentation (ARDS
  • ? extravasation of water
  • Hypoxemia
  • Lobar infiltrates
  • Stage 3 bronchopneumonia
  • Early Staph pneumonia (frequently PCN
  • Late - Pseudomonas

Inhalation Injury
  • Bronchoscopy
  • - erythema
  • - intraglottic soot
  • - ulceration

Grading of Burn Wounds
  • Mild lt 5 TBSA
  • Moderate 5-15 TBSA
  • Severe gt 15 (95 of burns seen)
  • May require Burn Unit care because of potential
    for disability despite small TBSA (face, hands,
    feet, perineum)

Area of Burn Rule of 9s

Note that a patient's palm is approximately 1
TBSA and can be used for estimating patchy areas.
Area of Burns - Pediatric
Estimation of Burn Wound Depth
  • Initial assessment is often unreliable
  • Ignore mild erythema when calculating fluid
  • Pink areas that blanch are usually superficial
  • Deeper wounds are dark red, mottled or pale and
  • Insensate areas are usually deep (3rd degree or

Factors Influencing Wound Depth
  • Temperature and duration
  • Thickness of skin (thin on eyelids, thick on
  • Age (children and elderly have proportionally
    thinner skin in comparison to adults)
  • Vascularity
  • Agent oil vs water acidic vs alkalotic
  • Time to definitive care

Burn Zones
  • Circumferential zones radiating from primarily
    burned tissues, as follows
  • Zone of coagulation - A nonviable area of tissue
    at the epicenter of the burn
  • Zone of ischemia or stasis - Surrounding tissues
    (both deep and peripheral) to the coagulated
    areas, which are not devitalized initially but,
    2 microvascular insult, can progress
    irreversibly to necrosis over several days if not
    resuscitated properly
  • Zone of hyperemia - Peripheral tissues that
    undergo vasodilatory changes due to neighboring
    inflammatory mediator release but are not injured
    thermally and remain viable

Zone of Hyperemia
Zone of Ischemia
Zone of Coagulation
Layers of the Skin
Categories of Burns First degree
  • Burns are divided into 4 categories, depending on
    the depth of the injury, as follows
  • First-degree burns are limited to the epidermis.
  • A typical sunburn is a first-degree burn.
  • Painful, but self-limiting.
  • First-degree burns do not lead to scarring and
    require only local wound care.

First degree Burn
Categories of Burns Second degree
  • Second-degree burns
  • point of injury extends into the dermis, with
    some residual dermis remaining viable
  • Partial thickness or Full thickness
  • those requiring surgery vs those which do not

Superficial Second degree Burn
Deep Second degree Burn
Categories of Burns Third degree
  • Third-degree or full-thickness burns involve
    destruction of the entire dermis, leaving only
    subcutaneous tissue exposed.

Third degree Burn
Escharatomy Sites
Preferred sites for escharotomy incisions. Dotted
lines indicate the escharotomy sites. Bold lines
indicate areas where caution is required because
vascular structures and nerves may be damaged by
escharotomy incisions. (From Davis JH, Drucker
WR, Foster RS, et al Clinical Surgery. St.
Louis, CV Mosby, 1987.)
Categories of Burns 4th degree
  • Fourth-degree burn is usually associated with
    lethal injury.
  • Extend beyond the subcutaneous tissue, involving
    the muscle, fascia, and bone.
  • Occasionally termed transmural burns, these
    injuries often are associated with complete
    transection of an extremity.

4th degree Burn
  • Physiologic Implications
  • Pathophysiology
  • Resuscitation
  • Post-Resuscitation
  • Board Questions

Physiologic Implications of Burn Injury
  • Predictable changes
  • Related to period of injury
  • Can be anticipated

Pathophysiology of Burns
  • Cell damage and death causes vasoactive mediator
  • Histamines
  • Thromboxanes
  • Cytokines
  • Increasing capillary permeability causes edema,
    third spacing and dehydration
  • Possible obstruction to circulation (compartment
    syndrome) and/or airway

Resuscitation Period
  • early ebb with late flow days 0-3
  • Hypodynamic, with need for close fluid
    resuscitation monitoring
  • Massive, diffuse capillary leak 2 to
    inflammatory mediators abates 18-24 hrs after
    injury and volume requirements abruptly decline
  • ? leak can be seen in those with delayed
    resuscitation 2 systemic release of O2 radicals
    upon reperfusion
  • Extravascular extravasation of fluid, lytes,
    colloid molecules
  • Other variables affect resuscitation preexisting
    fluid deficits, delay until treatment, inhalation
    injury, depth of wound
  • Must reevaluate resuscitation progress and
    endpoints frequently do not just use a formula

Resuscitation Guidelines
Postresuscitation Period
  • Day 3 until 95 wound closure
  • Hyperdynamic, febrile, protein catabolic state
  • Tachycardia can be normal in burn patients
  • Blood pressure may be hard to obtain due to
    circumferential burns
  • Release of more inflammatory mediators, cortisol,
    glucagon, catecholamines, bacteria from wound
  • High risk of infection and pain
  • Remove non-viable tissue or close wounds to avoid
  • Nutritional support essential
  • Maintain and support body temperature with high
    ambient temps and humidity

Recovery Period
  • 95 wound closure until 1 year post-injury
  • Continued catabolism and risk of non-healing
  • Anticipate septic events, treat complications,
    and continue nutritional support

Pathophysiology of Electrical Burns
  • Small cutaneous lesions may overlie extensive
    areas of damaged muscle ? myoglobin ?ARF.
  • Monitor for at least 48 hours after injury for
    cardiopulmonary arrest
  • May see vertebral compression fractures from
    tetanic contractions or other fractures from a
  • Visceral injury is rare but liver necrosis, GI
    perforation, focal pancreatic necrosis and
    gallbladder necrosis have been reported.
  • Look for motor and sensory deficitsmotor nerves
    are affected more than sensory nerves.
  • Thrombosis of nutrient vessels of the nerve
    trunks or spinal cord can cause late onset
    deficits. Early deficits are direct neuronal
  • Delayed hemorrhage can occur from affected
  • Cataracts may form up to 3 or more years after
    electrical injury
  • Microwave radiation damages tissues via a heating
    effect. Subcutaneous fatty tissue is often
    spared given its lower water content.

Burn Edema and Inflammation
  • Generalized edema found in burns gt 30 TBSA
  • Heat directly damages vessels and causes
  • Heat activates complement ? histamine release and
    more permeability ? thrombosis and coagulation

Systemic Response to Burn Injury
  • Accelerated fluid loss 2 leaky capillaries
  • ? Host resistance to infection
  • Multisystem Organ Failure
  • Infections in burns lt20 TBSA are well tolerated.
  • gt 40 TBSA with infection has very low survival
  • Initially ?CO, subsequent hypermetabolic state w/
    doubling of CO in 24 48 hours

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Burn Questions
Select the true statements regarding the
epidemiology of a burn injury
  • a. Scald burns are the most frequent forms of
    burn injury.
  • b. Flame burns are the most frequent forms of
    burn injury admitted to burn centers.
  • c. Burn injuries are most common among adults
  • d. About 15 of pediatric burn injuries are
    attributed to abuse or neglect.
  • e. Burn-related deaths are highest among

Select the true statements regarding the depth of

a. First-degree burns are physiologically
important and therefore considered when
calculating TBSA. b. Second-degree burns always
affect the epidermis and dermis of the skin. c.
Third-degree burns are very painful. d. All
first-degree burns heal within 2 to 3 days.
  • A 50 year-old man sustains a flame burn
    involving the entire upper left extremity, entire
    anterior trunk, genital area, and half of the
    left lower extremity. Approximately what
    percentage of the total body surface area is
  • a. 24
  • b. 28
  • c. 37
  • d. 45
  • e. 30

According to American Burn Association criteria,
which of the following patients should be
referred to a burn center?
  • A. Second- and third-degree burns involving more
    than 20 of the total body surface area (TBSA)
    in patients younger than 10 or older than 50
    years of age.
  • B. Full-Thickness burns that involve 2 of the
    TBSA in patients of any age.
  • C. Significant burns of the face, hands, feet,
    genitalia, perineum, or skin overlying major
  • D. Burn Injury in children with suspected or
    actual child abuse or neglect.
  • E. Acute massive skin loss syndromes (e.g.,
    Stevens-Johnson syndrome/toxic epidermal
    necrolysis, large traumatic de-gloving injuries)

All of the following are true regarding the
Pathophysiology of thermal injury, except?
  • A. Increased capillary permeability is due to
  • effect of heat and the liberation of
  • mediators.
  • B. Increased pulmonary vascular resistance
  • during the immediate postburn period.
  • C. Elevated thyronine (T3) and thyroxine (T4)
  • D. Elevated interleukin-6 (IL-6) level
  • E. Decreased immoglobulin G (IgG) level

  • A 60-year-old, 80-kg man has sustained a
    second-degree burn to 40 TBSA with a significant
    inhalation injury. He was admitted to the burn
    unit 30 minutes after the accident. According to
    the Parkland formula, resuscitation was started
    with lactated Ringers solution at 800 ml/hr.
    Six hours later the patient was found to be
    oliguric. What should be the next step in
    resuscitation of this patient?
  • A. Swan-Ganz catheter placement and measurement
    of pulmonary
  • wedge pressure.
  • B. Trial of small dose of furosemide
  • C. Low does of dopamine (2-3 ug/kg/min).
  • D. Increase in volume of the lactated Ringers
    solution infusion.
  • E. Bolus of colloid solution

Which of the following statements is/are true
regarding resuscitation of patients with burn
injury during the first 24 hours?
  • a. Parkland formula uses a balanced electrolyte
  • the fluid requirement is calculated as 3
  • body weight per TBSA burned.
  • b. Patients with 15 or more TBSA burn require
  • intravenous fluid resuscitation.
  • c. Adequate urine output implies hemodynamic
  • and adequate organ perfusion.
  • d. Crystalloid resuscitation restores cardiac
    output more rapidly
  • than colloid alone.
  • e. Late pulmonary morbidity and mortality are
    higher in colloid-
  • resuscitated patients.

Match the items in two columns
  • Topical Agents
  • A. Sodium mafenide
  • (Sulfamylon)
  • B. Silver nitrate 0.5
  • Solution
  • C. Silver sulfadiazine
  • (Silvadene)
  • Characteristics
  • A. Limited eschar penetration, resistant
    organisms neutropenia, thrombocytopenia
  • B. Painful application, hyperchloremic reactions
    good eschar penetration
  • C. Hyponatremia, hypokalemia, hypocalcemia,

Which of the following statements is/are true
regarding metabolism in the burn patient?
  • a. Postburn hypermetabolism is mediated by
  • release.
  • b. IL-1 and IL-6 are elevated in burn injuries
    and enhance the hypermetabolic response by
    increasing oxygen consumption.
  • c. Elevated core and skin temperature and lower
  • heat transfer are manifested in postburn
  • d. Increased blood flow to the muscles in the
    burned limb.
  • e. The burn wound preferentially utilizes glucose
  • anaerobic glycolytic pathways despite
    increased blood
  • flow to the wound.

Which of the following can minimize metabolic
expenditure in burn patients?
  • A. Nursing the patients at ambient temperature
    below 30oC.
  • B. Adequate analgesia and sedation.
  • C. Early excision of the burn and complete wound
  • D. Early diagnosis and treatment of infection.
  • E. Use of B-adrenergic blockers.

Select the correct statements regarding nutrition
in burn patients.
  • a. The optimal calorie/nitrogen ratio varies
    between 1501 1601.
  • b. Fat is the best source of non-protein calorie.
  • c. Glutamine deficiency results in atrophy of
    gut mucosa
  • d. Long-chain triglycerides for maintaining
    lean body mass.
  • e. Overfeeding is associated with

Which of the following statements is/are true for
invasive burn wound infection?
  • a. Common in burns larger than 30 total body
    surface area.
  • b. Characterized by conversion of a
    partial-thickness burn to full-thickness burn.
  • c. Definitive diagnosis can be made if
    quantitative culture of the biopsy recovers more
    than 105 organisms per gram on tissue.
  • d. Incidence of Candida wound infection has
    increased owing to topical antimicrobial
  • e. Topical antimicrobial agents have markedly
    decreased the incidence of invasive burn wound

Select the true statements regarding infection in
the burn patient
  • a. Infection if the most frequent cause of death
    in the burn patients.
  • b. Cell-mediated immunity is not altered in major
    burn injuries.
  • c. Hematogenous pneumonia is the most common
    pulmonary infection in burn patients.
  • d. Diminished granulocyte chemotaxis is an
    important factor in burn infection.
  • e. Suppurative thrombophlebitis can be a major
    source of sepsis.

Which of the following statements is/are true
regarding administration of antibiotics to burn
  • a. Prophylactic systemic antibiotics are
    indicated in patients with extensive burns.
  • b. With invasive burn wound sepsis, systemic
    antibiotics should not be instituted before
    culture and sensitivity results are available.
  • c. Positive wound cultures should be treated
    with systemic antibiotics.
  • d. Antibiotics effective against anaerobic
    organisms are always indicated for burn wound
  • e. Subtherpeutic serum antibiotic levels are
    common in burn patients.

Which of the following statements is/are true
regarding burn wound excision?
  • A. Excision is indicated for deep
    partial-thickness and full- thickness burn
  • B. Early excision and closure of burn wounds
    has been shown to reduce the incidence in
    invasive burn wound infection, shorten the
    hospital stay, reduce pain, and improve
    functional recovery.
  • C. Excision should be performed after
    successful fluid resuscitation.
  • D. Tangential excision involves sequential
    excision of the eschar down to bleeding,
    viable tissue.
  • E. Excision of more than 10 of TBSA single
    procedure is associated with significantly

Which of the following statements is/are true
regarding burn wound closure?
  • A. Split-thickness autograft is
    contraindicated if wound culture is positive
    B-hemolytic streptococci.
  • B. Xenograft is the most frequently used and
    effective biologic dressing when an autograft
    is not available.
  • C. Allograft dressings promote bacterial
  • D. Cultured autologous keratinocyte sheets can
    be used for permanent wound coverage with good
  • E. Dermal substitutes provide better temporary
  • coverage that biologic dressings.

Select the true statements regarding inhalation
  • A. Presence of carbonaceous sputum is a
    specific sign of inhalation injury.
  • B Normal carbon monoxide level on admission
    excludes inhalation injury.
  • C. Chest radiography is sensitive for
    diagnosing inhalation injury.
  • D. Combined fiberoptic bronschosocpy and 133 Xe
    ventilation-perfusion lung scan has a diagnostic
    accuracy of more than 96
  • E. Pulmonary infection is the most frequent
    cause of morbidity and mortality with inhalation

Select the correct statements regarding
electrical injury.
  • a. Depth of tissue injury is related to density
    and duration of the current flow.
  • b. High-voltage electric injury results in more
    severe injury to the trunk than the extremities.
  • c. Risk of acute renal failure is relatively
    high with an electrical injury due to
    myoglobinuria and underestimation of fluid
  • d. Incidence of cholelithiasis is high in
    patients after electrical injury.
  • e. With a lightening injury cardiopulmonary
    arrest is common, and burns are
    characteristically superficial.

Which of the following statements is/are true
regarding chemical injuries?
  • a. Immediate wound care involves application of
    a neutralizing agent.
  • b. Acid burns cause liquefaction necrosis.
  • c. Alkali burns produce deeper injuries than
    acid burns.
  • d. Hydrofluoric acid burn is treated with local
    calcium gluconate gel.
  • e. Coal tar burn is best treated with immediate
    application of a petroleum-based ointment.

Select the true statements regarding post burn
  • A. All second third degree burns produce
    permanent scarring.
  • B. The incidence of hypertrophic scar formation
    is less after excision and skin grafting than
    with wounds that heal spontaneously.
  • C. Hypertrophic scars are best treated by early
    excision and wound closure.
  • D. Basal cell carcinoma is the most common
    carcinoma in an old burn scar.