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PATHOPHYSIOLOGY
OF BURNS
Dr. Shiara Ortiz-Pujols
Burn Fellow
NC Jaycee Burn Center
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Objectives
PART 1
Anatomy Overview
Causes of Burns
Estimating Burns(Depth & %)
Categories & Zones
PART 2
Physiologic
Implications
PathophysiologyResuscitation
Post-Resuscitation
Board Questions
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Anatomy
Adult skin surface 1.5-2.0 m2 (0.2-0.3 innewborns); largest organ
Skin thickness 1-2 mm; peaks age 30-40; M>
F Functions include:
protection from external environment
maintenance of fluid/electrolyte homeostasis
Thermoregulation
immunologic function
sensation
Metabolic organ (i.e., Vit D synthesis)
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Causes of Burns
Usually caused by heat, electricity, chemicals,radiation, and friction
Thermal burns are caused by steam, fire, hotobjects 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 tothe sun, tanning booths, sun lamps, X-rays orradiation from cancer treatments
Friction burns occur when skin rubs against ahard surface, e.g. carpet, gym floor, concrete or a
treadmill
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Effect of Heat
Temporal and quantitative
40-44C, enzymes malfunction, proteins
denature and pumps fail
> 44C, damage occurs faster than repair
mechanisms can keep up with
Damage continues even when thesource is withdrawn
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Effect of Electricity
Effects of current dependon several factors
- Type of circuit
- Voltage
- Resistance ofbody
- Amperage
- Pathway ofcurrent
- Duration of contact
High voltage (>1000V)causes underlying tissuedamage. Deep tissuesact as insulators andcontinue to be injured.
Resistance of varioustissues from LH:nerve, vessels, muscle,skin, tendon, fat, bone
Ohms Law- V=IR
Damage more related tocross-sectional areawhich explains extremityinjuries without trunkinjuries.
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Electrical Storms/Lightning
Burns are characteristically
superficial and present as a
spidery or arborescent
pattern.
Cardiopulmonary arrest iscommon 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 survivinglightning strikes is Roy C.Sullivan who was a parkranger from VA. Roy wasstruck 7 times from 1942-
1977.
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Electrical Pruning
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Effect of Chemicals
Acids and alkalis cause injury viadifferent mechanisms.
Petroleum products can causedelipidation and depth ofwound 2 tendency to adhere toskin
Acids:
coagulation necrosis
denaturing proteins upon tissuecontact
area of coagulation is formed
and limits extension of injury exception is hydrofluoric
acid, which produces aliquefaction necrosis similar toalkalis.
Acid damaged skin can look
tanned and smooth; do notmistake for a suntan.
Alkalis:
liquefaction necrosis
potentially moredangerous than acidburns
liquefy tissue bydenaturation of proteins andsaponification of fats
In contrast to acids, whosetissue penetration islimited by the formation ofa coagulum, alkalis cancontinue to penetrate verydeeply into tissue
Can cause severeprecipitous airway edema
or obstruction.
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Inhalation Injury
Heat dispersed in upper airways leads to edema
Cooled smoke and toxins carried distally
Increased blood flow to bronchial arteries
causes edema Increased lung neutrophils mediators of
lung damage release proteases andoxygen free radicals (ROS)
Exudate in upper airways formation of fibrincasts
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Stages of Inhalation Injury
Stage 1 acute pulmonary insufficiency
Signs of pulmonary failure at presentation
Stage 2 72-96 hrs after presentation (ARDS
picture) extravasation of water Hypoxemia
Lobar infiltrates
Stage 3 bronchopneumonia Early Staph pneumonia (frequently PCN resistant)
Late - Pseudomonas
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Inhalation Injury
Bronchoscopy:
- erythema
- intraglottic soot
- ulceration
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Grading of Burn Wounds
Mild: < 5% TBSA
Moderate: 5-15% TBSA
Severe: > 15% (95% of burns seen)
May require Burn Unit care because of
potential for disability despite small TBSA (face,hands, feet, perineum)
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Area of BurnRule of 9s
Note that a patient's palm is approximately 1% TBSA and can be used for estimating patchy areas.
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Area of Burns - Pediatric
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Estimation of Burn Wound
Depth
Initial assessment is often unreliable
Ignore mild erythema when calculating fluid
requirements
Pink areas that blanch are usually superficial
Deeper wounds are dark red, mottled or pale
and waxy
Insensate areas are usually deep(3rd degree orgreater)
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Factors Influencing Wound
Depth
Temperature and duration
Thickness of skin (thin on eyelids, thick on back)
Age (children and elderly have proportionally
thinner skin in comparison to adults)
Vascularity
Agent oil vs water; acidic vs alkalotic
Time to definitive care
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Burn Zones
Circumferential zones radiating from primarily burned
tissues, as follows:
1. Zone ofcoagulation - A nonviable area of tissue at the
epicenterof the burn
2. Zone ofischemia or stasis - Surrounding tissues (both deepand peripheral) to the coagulated areas, which are not
devitalized initially but, 2microvascular insult, can progress
irreversibly to necrosis over several days if not resuscitated
properly
3. Zone ofhyperemia - Peripheraltissues that undergovasodilatory changes due to neighboring inflammatory mediator
release but are not injured thermally and remain viable
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Zone of
Coagulation
Zone of
Ischemia
Zone of
Hyperemia
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Layers of the Skin
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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.
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First degree Burn
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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
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Superficial Second degree Burn
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Deep Second degree Burn
C i f B Thi d
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Categories of Burns Third
degree
Third-degreeor full-thickness burns
involve destruction of the entire
dermis, leaving only subcutaneous
tissue exposed.
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Third degree Burn
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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.)
C t i f B 4th
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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.
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4th degree Burn
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PART 2
Physiologic Implications
Pathophysiology
ResuscitationPost-Resuscitation
Board Questions
Ph i l i I li ti f B
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Physiologic Implications of Burn
Injury
Predictable changes
Related to period of injury
Can be anticipated
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Pathophysiology of Burns
Cell damage and death causes vasoactive mediator
release:
Histamines
Thromboxanes
Cytokines
Increasing capillary permeability causes edema, third
spacing and dehydration
Possible obstruction to circulation (compartmentsyndrome) and/or airway
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Resuscitation Period
early ebb with late flow; days 0-3
Hypodynamic, with need for close fluid resuscitationmonitoring
Massive, diffuse capillary leak2 to inflammatory mediators; abates
18-24 hrsafter injury and volume requirements abruptly decline
leak can be seen in those with delayed resuscitation 2 systemicrelease of O2 radicals upon reperfusion
Extravascularextravasation of fluid, lytes, colloid molecules
Other variables affect resuscitation: preexisting fluid deficits, delay untiltreatment, inhalation injury, depth of wound
Must reevaluate resuscitation progress and endpoints frequently; do not
just use a formula
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Resuscitation Guidelines
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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 sepsis
Nutritional support essential Maintain and support body temperature with high ambient temps
and humidity
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Recovery Period
95% wound closure until 1 year post-injury
Continued catabolism and risk of non-healing
wound
Anticipate septic events, treat complications,and continue nutritional support
Pathoph siolog of Electrical
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Pathophysiology of Electrical
Burns Small cutaneous lesions may overlie extensive areas of damaged musclemyoglobinARF.
Monitor for at least 48 hours after injury for cardiopulmonary arrest
May see vertebral compression fracturesfrom tetanic contractions orother fractures from a fall.
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 causelate onset deficits. Early deficits are direct neuronal injury.
Delayed hemorrhage can occur from affected vessels
Cataracts may form up to 3 or more years after electrical injury
Microwave radiation damages tissues via a heating effect. Subcutaneousfatty tissue is often spared given its lower water content.
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Burn Edema and Inflammation
Generalized edema found in burns > 30%TBSA
Heat directly damages vessels and causes
permeability Heat activates complement histaminerelease and more permeability thrombosisand coagulation systems
+
Systemic Response to Burn
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Systemic Response to Burn
Injury
Accelerated fluid loss 2 leaky capillaries
Host resistance to infection Multisystem Organ Failure
Infections in burns 40% TBSA with infection has very low survivalrate
Initially CO, subsequent hypermetabolic statew/ doubling of CO in 24 48 hours
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OR Pictures
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Burn Questions
Select the true statements regarding the
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Select the true statements regarding the
epidemiology of a burn injury
a. Scald burns are the most frequent forms of burninjury.
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 attributedto abuse or neglect.
e. Burn-related deaths are highest among adults.
Select the true statements regarding the
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Select the true statements regarding the
depth of burn
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.
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A 50 year-old man sustains a flame burninvolving the entire upper left extremity, entireanterior trunk, genital area, and half of the left
lower extremity. Approximately what percentageof the total body surface area is burned?
a. 24%
b. 28%
c. 37%d. 45%
e. 30%
According to American Burn Association criteria,f f f
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which of the following patients should be referredto a burn center?
A. Second- and third-degree burns involving more than 20%of the total body surface area (TBSA) in patients youngerthan 10 or older than 50 years of age.
B. Full-Thickness burns that involve 2% of the TBSA inpatients of any age.
C. Significant burns of the face, hands, feet, genitalia,perineum, or skin overlying major joints.
D. Burn Injury in children with suspected or actual childabuse 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
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All of the following are true regarding the
Pathophysiology of thermal injury, except?
A. Increased capillary permeability is due todirect
effect of heat and the liberation of vasoactive
mediators.B. Increased pulmonary vascular resistance
occursduring the immediate postburn period.
C. Elevated thyronine (T3) and thyroxine (T4)levels.
D. Elevated interleukin-6 (IL-6) levelE. Decreased immoglobulin G (IgG) level
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A 60-year-old, 80-kg man has sustained a second-degreeburn to 40% TBSA with a significant inhalation injury. He wasadmitted to the burn unit 30 minutes after the accident.
According to the Parkland formula, resuscitation was startedwith lactated Ringers solution at 800 ml/hr. Six hours laterthe patient was found to be oliguric. What should be the nextstep in resuscitation of this patient?
A. Swan-Ganz catheter placement and measurement ofpulmonary
wedge pressure.B. Trial of small dose of furosemideC. 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
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regarding resuscitation of patients with burn
injury during the first 24 hours?
a. Parkland formula uses a balanced electrolyte solution& the fluid requirement is calculated as 3 ml/kgbody weight per %TBSA burned.
b. Patients with 15% or more TBSA burn require
intravenous fluid resuscitation.c. Adequate urine output implies hemodynamic stability
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.
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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 escharpenetration, resistant
organisms neutropenia,thrombocytopenia
B. Painful application,hyperchloremic reactionsgood eschar penetration
C. Hyponatremia,hypokalemia,hypocalcemia,methemoglobinemia
Which of the following statements is/are true
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Which of the following statements is/are trueregarding metabolism in the burn patient?
a. Postburn hypermetabolism is mediated by catecholamine
release.
b. IL-1 and IL-6 are elevated in burn injuries and enhance thehypermetabolic response by increasing oxygenconsumption.
c. Elevated core and skin temperature and lower core-to-skin
heat transfer are manifested in postburn hypermetabolism.
d. Increased blood flow to the muscles in the burned limb.
e. The burn wound preferentially utilizes glucose by
anaerobic glycolytic pathways despite increased blood
flow to the wound.
Which of the following can minimize
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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 woundclosure.
D. Early diagnosis and treatment of infection.
E. Use ofB-adrenergic blockers.
Select the correct statements regarding
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Select the correct statements regarding
nutrition in burn patients.
a. The optimal calorie/nitrogen ratio variesbetween 150:1 & 160:1.
b. Fat is the best source of non-proteincalorie.
c. Glutamine deficiency results in atrophyof gut mucosa
d. Long-chain triglycerides for maintaining
lean body mass.e. Overfeeding is associated with
hyperventilation.
Which of the following statements is/are true
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gfor invasive burn wound infection?
a. Common in burns larger than 30% total bodysurface area.
b. Characterized by conversion of a partial-thickness burn to full-thickness burn.
c. Definitive diagnosis can be made ifquantitative culture of the biopsy recoversmore than 105 organisms per gram ontissue.
d. Incidence of Candida wound infection hasincreased owing to topical antimicrobialchemotherapy.
e. Topical antimicrobial agents have markedlydecreased the incidence of invasive
Select the true statements regarding
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Select the true statements regardinginfection in the burn patient
a. Infection if the most frequent cause of deathin the burn patients.
b. Cell-mediated immunity is not altered inmajor burn injuries.
c. Hematogenous pneumonia is the mostcommon pulmonary infection in burnpatients.
d. Diminished granulocyte chemotaxis is animportant factor in burn infection.
e. Suppurative thrombophlebitis can be a majorsource of sepsis.
Which of the following statements is/are trueregarding administration of antibiotics to
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regarding administration of antibiotics toburn patients?
a. Prophylactic systemic antibiotics areindicated in patients with extensive burns.b. With invasive burn wound sepsis,
systemic antibiotics should not beinstituted before culture and sensitivityresults are available.
c. Positive wound cultures should be treated
with systemic antibiotics.d. Antibiotics effective against anaerobicorganisms are always indicated for burnwound sepsis.
e. Subtherpeutic serum antibiotic levels are
Which of the following statements is/are
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Which of the following statements is/are
true regarding burn wound excision?
A. Excision is indicated for deep partial-thickness and full-thickness burn wounds.
B. Early excision and closure of burn wounds has beenshown 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 fluidresuscitation.
D. Tangential excision involves sequential excision of theeschar down to bleeding, viable tissue.
E. Excision of more than 10% of TBSA single procedure isassociated with significantly morbidity.
Which of the following statements is/are true
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Which of the following statements is/are true
regarding burn wound closure?
A. Split-thickness autograft is contraindicated ifwound culture is positive B-hemolytic
streptococci.
B. Xenograft is the most frequently used andeffective biologic dressing when an
autograft is not available.
C. Allograft dressings promote bacterial
proliferation.D. Cultured autologous keratinocyte sheets can
be used for permanent wound coverage
with good results.
Select the true statements regarding
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Select the true statements regarding
inhalation injury.
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 injury.
Select the correct statements
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Select the correct statementsregarding electrical injury.
a. Depth of tissue injury is related to density andduration of the current flow.
b. High-voltage electric injury results in more severeinjury to the trunk than the extremities.
c. Risk of acute renal failure is relatively high with anelectrical injury due to myoglobinuria andunderestimation of fluid needs.
d. Incidence of cholelithiasis is high in patients afterelectrical injury.
e. With a lightening injury cardiopulmonary arrest iscommon, and burns are characteristically superficial.
Which of the following statements is/are true
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Which of the following statements is/are trueregarding chemical injuries?
a. Immediate wound care involves application of aneutralizing agent.
b. Acid burns cause liquefaction necrosis.
c. Alkali burns produce deeper injuries than acid burns.
d. Hydrofluoric acid burn is treated with local calciumgluconate gel.
e. Coal tar burn is best treated with immediateapplication of a petroleum-based ointment.
Select the true statements regarding
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g gpost burn sequelae
A. All second & third degree burns producepermanent scarring.
B. The incidence of hypertrophic scar formation isless 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.