Burns : Types, Classification, Symptoms and Treatment

Burns are tissue injuries caused by thermal, radiation, chemical, or electrical contact resulting in protein denaturation, loss of intravascular fluid volume due to increased vascular permeability and edema.

Etiology of burns

Chemical, Thermal, Electrical, Mechanical, Radiation, Frostbite

Persons at Risk of burns

1.Extremes of age - the very young (<4yrs) or very old (>50yrs)

2. Those whose ability to protect themselves is impaired or prone to accidents Alcoholics, Sick, paraplegics, diabetics, psychiatric patients and patients of convulsive disorders

3.The unlucky - Innocent bystander

4.The careless - Storing petrol in the house, adding paraffin to a lit stove, smoking in bed, working close to high tension electric wires

Skin Anatomy and Function

Skin is the largest organ of the body. It is 0.025 m² in children and 1.8m² in adults. It has 3 major tissue layers.

 Epidermis

This is the outermost layer, the epidermis, is composed of stratified epithelium.

The epidermis has two components, an outer layer of anucleate cornified cells (stratum corneum) that covers inner layers of viable cells (Malpighian layers) from which the cornified surface cells arise by differentiation.

The stratum corneum acts as a barrier to impede the entrance of microorganisms and toxic substances while allowing the body to retain water and electrolytes. Malpighian layers provide continuous production of cornified cells.

Malpighian layers can be further subdivided into the germinal basal cell layer, stratum spinosum, and stratum granulosum

Dermis

Beneath the epidermis is the dermis, which is composed of a dense fibroelastic connective-tissue stroma containing collagen and elastic fibers and an extracellular gel termed ground substance.

The dermal layer contains an extensive vascular and nerve network, special glands, and appendages that communicate with the overlying epidermis.

The dermis is divided into two parts.

1. a) The most superficial portion, the papillary dermis, is molded against the epidermis and contains superficial elements of the microcirculation of the skin. Within the papillary dermis, dermal elevations indent the inner surface of the epidermis
2. b) In the reticular portion of the dermis, collagen and elastic fibers are thicker and greater in number. Fewer cells and less ground substance are found in the reticular dermis than in the papillary dermis

Subcutaneous tissue

The third layer of skin is subcutaneous tissue, which is composed primarily of areolar and fatty connective tissue. This layer shows great regional variations in thickness and adipose content. It contains skin appendages, glands, and hair follicles

Functions of skin                                 

1.Protect entry of micro-organism

2,.Protect against UV light

3.Vitamin D synthesis

4. Homeostasis-Thermoregulation and prevent excess water loss

5.Cosmesis,  beauty and identification-finger prints

Pathophysiology  of Burns

Tissue damage due to the above agents leads to the release of vasoactive substances e.g. prostaglandins, histamines, oxygen radicals, leukotrienes, and platelet-activating factors. These substances cause microvascular instability with increased capillary permeability for the first 24-36hours of fluid shift to the extravascular compartment and edema. This leads to decreased right atrial filling pressures decreased cardiac output and Shock.

The body tries to compensate for these physiological changes by

• Increased peripheral resistance (sympathetic stimulation)
• Tachycardia
• The decreased capacitance of great vessels

If the process goes uncorrected;

• Cardiac output is diverted to vital tissues reducing perfusion of skin, muscle, and gut - Skin feels cold and clammy
• Reduced renal perfusion lead to acute renal injury.

Irreversible shock occurs as an end-stage with falling Blood pressure, cardiac output and pulse rate.

In patients with serious burns, the release of catecholamines, vasopressin, and angiotensin causes peripheral and splanchnic bed vasoconstriction that can compromise in-organ perfusion

Myocardial contractility also may be reduced by the release of inflammatory cytokine TNF-alpha

In deep third-degree burns, hemolysis may be encountered, necessitating blood transfusions to restore blood loss

A decrease in pulmonary function can occur in severely burned patients without evidence of inhalation injury from the bronchoconstriction caused by humoral factors, such as histamine, serotonin, and thromboxane A2.

A decrease in lung and tissue compliance is a manifestation of this reduction in pulmonary function.

Burned skin exhibits an increased evaporative water loss associated with an obligatory concurrent heat loss, which leads to dehydration and hypothermia.

Classification of burns

1. According to Cause;

1.Thermal

Open flames and Hot liquid are most common (heat usually ≥15-45°C).

2.Caustic chemicals or acids (may show little signs or symptoms for the first few days).

Mechanisms of injury:

Extravasation

Due to drug leakage into tissues e.g. All Cytotoxics, Sulphur drugs, Potassium drugs,  bismuth drugs: They cause Inflammation and vesicles; Skin necrosis may occur within 24 hours and Gangrene secondary to vascular spasm in 2-3days.

Management is by prevention and close monitoring, IV line in the forearm and flush line well.

Once it occurs –stop drugs and Apply normal saline gauze and change every 2 hours

Contact injury

Types of contact injury include:

-Local chemical reaction

-Thermal injuries

-Inhalational injuries (chemical pneumonitis and bronchospasm)

-Systemic poisoning

Acids - cause severe superficial coagulative necrosis. Burning stops within 1-2 hours for hydrochloric acid and sulphuric acid & 7-14 days for HOCL
The amount ingested does not contribute to the extent of the injury.

Initial management is to pour a lot of water for long 1-2 hours, dress with clean material and control pain.

You can excise area to prevent a continued reaction

-Usually, the graft take is very disappointing

Alkali - Causes deep liquefactive necrosis - penetrate tissue by saponification (Fat +alkali) , hydrolyzing structural proteins & dissolving cells along its course thus amount ingested contributes to the extent of the injury. The burn runs for 7-14 days.

Management - Generously irrigate with fluid for 1-2 hours & Dress in gauze soaked in NS or Ice 2-3hrly.

DO NOT try to neutralize the chemical.

Exercise the area to prevent a continued reaction.

3.Electricity

Types of electricity are: low voltage, high voltage, and very high voltage

Low voltage is <1000 volts while high voltage is > 1000 volts. Very high voltage include injury from the grid and lightning injuries

Electrical burns have entry and exit points.

Main injuries are

-Myonecrosis, Renal failure, and heart arrhythmia

-Myonecrosis leads Myoglobinuria causing to Renal failure with very little damage to overlying skin.

-Arching burn -Occur around joints due to burning at joint surrounded by two areas of conductance.

-Side flash-Very high voltage burns due to lightening.

-Body resistance is about 500ohms. A current of 1 ampere is required to cause cardiac asystole this usually does not occur with domestic electric burns because the voltage is about 240V giving current of approx. O.5 A.

Thus Total body surface area (TBSA) is NOT an index for resuscitation. IV fluids are titrated against the volume of urine & specific gravity (1.010). Usually, double the physiological requirements (3L/24hrs) of the patient.

-In microwave injuries, the area is normal-looking but anesthetic due to depolarization of nerves.

-Flash burns occur in technicians & may resemble open flame burns.

Management is by giving plenty of fluids.

Alkalinizing the urine and administration of mannitol aid in flushing the myoglobin from the kidney.

Do fasciotomy of the muscle compartment to avoid Compartment syndrome. Normal pressure is 30mmHg

Debride after 3-4 days

4.Frostbite

5.Mechanical (Frictional) burns

6.Radiation injury

2.According to Depth of Injury

Depth of burn is proportional to;

• Temperature applied
• Duration of contact
• The thickness of the skin
• Heat capacity of the agent
• Transfer coefficient
• The specific heat and conductivity of the local tissues

The depth of injury determines the formation of scar tissue.

1st Degree Burns;

In the first degree, the epidermis is the only part involved.
Commonly caused by UV light or very short flash or flame exposure. Skin is red, dry & hypersensitive thus painful.

No treatment except analgesia.
Leaves no scarring on healing.

2nd Degree Burns;

  Superficial 2nd Degree

Epidermis plus the upper third ( ⅓) of Dermis are involved.
Commonly caused by scald (spill or splash).
Red, moist, weeping, cause blisters that Blanche with pressure.
Painful due to nerve exposure and heals from 10-14 days.

Leaves no scarring on healing but there are potential pigment changes

   Deep 2nd Degree

Epidermis upper two thirds ( ⅔) of Dermis are involved.

Commonly caused by scald, flame, chemicals, oil & grease.
Cheesy white, wet or waxy dry; Does not Blanche with pressure

Healing takes 14-21 days

There are severe scarring and risk of contractures.

3rd Degree Burns (Full Thickness Burns);

Full Epidermis + Dermis are destroyed leaving no cells to heal and extend to the subcutaneous tissue.

Commonly caused by scald, steam, flame, chemicals, oil, grease & high voltage electricity.
Grey to charred & black, insensate, contracted, pale, leathery tissue

Severe scarring & high risk of contractures

4th Degree Burns            

Muscle involvement

5th Degree Burns

Bone involvement - Especially in epileptics who convulse during burning

C.According to Size of Burn

Determines the extent of fluid loss.

i)Wallace Rule of Nines - used in Adults to estimate BSA (Body Surface Area)

ii)American Burns Association Severity

iii) Lund-Browder Chart for estimating the extent of burns in Children.

1. Zones of a burn wound

1.Center-coagulate necrosis

2.Immediate area-zone of stasis

3.Further-zone of hyperemia

Depth of wound estimation

Clinical Appearance, Pinprick test, use of dye.

Imaging by ultrasound or MRI.

Major or Severe Burns also includes;

1. High voltage electrical burns
2. Significant burn to face, eyes, ears, fingers, feet, joints, or genitalia
3. Significant associated injuries e.g. fractures & other major trauma
4. Inhalational Injuries

Inhalational injury

Classified as supraglottic, subglottic , or Global

Causes upper airway obstruction secondary to;

Reflex Laryngospasm

Edema

Sloughing of the mucosa, reduced clearance blockage and infection( Pneumonia)

Clinical presentation

History of having been injured in an enclosed space e.g. house, motor vehicle

Physical examination

• Facial burns
• Soot is seen in nasopharynx
• Respiratory distress- Tachypnoea - ≥25 breaths/min, Stridor, flaring of alae nasae
• Coughing up carbonaceous sputum/soot
• Hoarseness of voice (will indicate vocal cord swelling)

Management

1) Admit patient to High dependency care or ICU

2) Intubate the earliest opportunity to avoid difficulty once edema sets in.

Tracheostomy is indicated in the first several days for patients who are expected to require ventilatory support for a few weeks or more.

If the neck is burned, excision and grafting followed by tracheostomy is indicated in order to improve pulmonary toilet.

3) Give 100% O2 by Mask or Endotracheal tube in serious inhalational injury. Should be moist the humidity will help loosen the secretions and prevent drying of the airway;

4) Bronchodilators by aerosol or aminophylline intravenously may help if wheezing is due to reflex bronchospasm.

5) Suction /lavage of bronchial secretions (bronchial toilet)

6) Chest physiotherapy with postural drainage is also required.

7) Bronchoscopy to evaluate the extent of the inhalational injury at the same time do bronchial toilet

8) Investigation-Measure carboxyhemoglobin; With 100% O2, t½ of CO Hb falls from 250mins to 40mins

Others investigations

• Arterial blood gas analysis
• Hemoglobin levels
• Chest X-ray

NB:-Pulse oximetry is unreliable (may be normal) and patients need about 10-15 % more of IV fluid calculated.

Rescue & First Aid

General considerations;

Electric burns - turn off mains before touching the patient

If the victim's clothes are on fire - Stop, Drop & Roll. Can cover with a blanket to put off the fire

1st Degree Burns;

Cool burned area of skin for 5-10mins (running water, cool compress or towel, immersion in cold water)

After 10mins, dry area & keep the patient warm to avoid hypothermia

Drink lots of fluids - Sweetened water with a pinch of salt PRN

Analgesics ± Anti-inflammatories e.g. Ibuprofen or Acetaminophen

Cover burn with a cool sterile dressing

2nd Degree Burns;

Call Emergency services

DO NOT break or drain the blisters

DO NOT remove/ peel-off stuck clothing

Cool burned area of skin for 5-10mins (running water, cool compress or towel, immersion in cold water)

Once immersed in cool water, carefully remove clothing & jewelry on the burnt area

After 10mins, dry area & keep the patient warm to avoid hypothermia

Evaluate for signs of shock & treat accordingly

Elevate burnt area if possible

Cover burn with cool sterile dressing - DO NOT apply ointment, lotion or anything.

Indications for Admission

A) Cause;

1)Electrical burns including lightning injuries

2)Chemical burns with a serious threat of function or cosmetic impairment

B) Severity;

1) Moderate & Severe burns

2) 3rd & 4th Degree burns regardless of TBSA

3) Non-healing burns after 14-21 days

C) Anatomical location;

1)Head, neck, hands, soles, Perineum

2)Circumferential limb burns

3)Burns to the back

4) All inhalational injuries

D) Patient factors;

1) Extremes of age (<4yrs & >50yrs).

2) Burns of both limbs in an Obese patient.

3) Pregnancy.

4) Any burn with concomitant trauma in which the injury poses the greatest risk of morbidity or mortality.

5) Burn injuries with pre-existing medical disorders that could complicate management, prolong recovery or affect mortality e.g.

• Diabetes and Hypertension
• Epilepsy
• Blind or Deaf
• Infection
• Renal problems

Casualty and Ward Management Goals

The first 48 hours

All efforts are towards resuscitation & saving lives

48 hours -6 months

Aim to prevent complications

More than 6 months

Reconstructive surgery, Rehabilitation,  Training

Management for the first 48 hrs

On arrival at casualty

1.Primary Survey

Airway with cervical spine control (Look out for & manage inhalational injury), Breathing, Circulation & hemorrhage control, Disability & Exposure

At this point insert a large-bore intravenous cannula.

Central Venous Pressure  Monitor (CVP)

Urethral catheterization

Nasogastric tube.

Endotracheal intubation if an inhalational burn

2.Secondary Survey

History of the burn

Physical examination from the head toe - Calculation of the    BSA

3.Medical Management

4. IV Fluids

For Moderate & Major/Severe Burns use the following common formulas to estimate the required fluids.

Parkland's Formula

 4mL /Kg / Total body surface area

Crystalloids: Ringers Lactate or Hartmann's solution, NS

Give ½ within 8 hours since the burn occurred and the rest in the next 16 hours(most fluid losses occur 8-12 hours after the burn)

Give ~50% more in electrical burns & inhalational injury

1-Monitoring of fluid therapy

Adequate resuscitation is measured by urine output; (best guide).
In adults - 30-50mls/hr and Children - 0.5-1ml /Kg/hr.

Increase rate of infusion if the urine is less than 20ml/hr and decrease rate of infusion if the urine output greater than 60ml/hr because of the risk of pulmonary edema especially in inhalational injury

However, in electrical burns aim for 100ml /hr of urine to flush the kidney. Alkalization of the urine by adding sodium bicarbonate to the IV fluid increases the solubility and clearance rate of myoglobin in the urine

Hemoglobinuria suggest deep burn hence flush the kidney with increased fluids and mannitol

A decrease in BP and urine output suggest the need for colloids but a decrease in urine output but normal BP suggest need for crystalloids

2- Pulse and BP recording. The pulse should be  less than 120/minute

3-State of the patient should be calm

4--Frequent chest auscultation  to detect pulmonary edema

5-Cerebral edema, especially in children, may occur during fluid therapy

6-If possible CVP line is the best to guide for avoiding over infusion

7-Evaluate treatment every 3-4 hours

Causes of inadequate fluid resuscitation in a burns patient

An inaccurate estimate of burn size, Undiagnosed

Other formulas for calculating fluids include:

1.Evans Formula

2ml/Kg/total body surface area

NB-TBSA only up to 50 %

The total fluid is given as a mixture of colloids and crystalloids in the ration of 1:1.

Colloid include blood and blood products- plasma, albumin, dextrans, Gelatins as haemacele and Gelofulsine

Crystalloids are Normal Saline, Hartmans solutions

Add 2000ml(2L) of 5% dextrose for insensible losses

Half of all the fluids given in the 1st 8 hrs since the occurrence of burn and the rest in the next 16 hours

After 24 hours give half of the fluids (1ml/kg/BSA) plus the 2L of 5 % dextrose.

2.Brook  Army formula

2ml/Kg/total body surface area

NB-TBSA only up to 50 %

The total fluid is given as a mixture of crystalloids and colloids in the ratio of 1.5:0.5 respectively

Colloid include plasma, blood, dextrans, albumin

Crystalloids are Saline, Hartmans solutions

Add 2000ml(2L) of 5% dextrose for insensible losses

Half of all the fluids given I the 1st 8 hrs since the occurrence of burn and the rest in next 16 hours

After 24 hours give half of the fluids (1ml/kg/BSA) plus the 2L of 5 % dextrose.

ii)Analgesics

Give opiate analgesics IV (IM is ineffective erratic absorption); NSAIDs

iii)PPI or H2 Blocker

protection from Curling's Ulcers (duodenal ulcers which occur in burned patients)

iv)Tetanus toxoid

v) Prophylactic antibiotics If TBSA >15%

If less do M/C and sensitivity before antibiotic  administration

vi) Optional Drugs

DVT prophylaxis in lower limb burns

Tetracycline eye ointment for Face burns

Insulin if Diabetic or hypertensive control if hypertensive

Wound care

i)Remove all necrotic tissue & debris

ii)Rupture blisters except those on the palms & soles of feet and those>1cm in diameter. Can do early escharotomy and grafting

iii)Wash wound with soap & water or normal saline

iv)Apply topical antibiotic e.g.

Silver sulphadiazine (Side effects are thrombocytopenia, leucopenia, rash-sulfonamide sensitivity)

0.5% Silver Nitrate - Stains tissues & can cause hypochloraemic alkalosis & hyponatremia; Good for grafts

Mafenide 10% - can penetrate tissue & eschar. Good for infected wounds & eschars. very painful on application

Neosporin or Bacitracin - Good for facial burns as they are not toxic to the eyes

OR - Apply antibiotic-impregnated material

Dressing

Open Dressing - No dressing applied

Exposure Dressing - Apply soothant e.g. Vaseline

Occlusive dressing e.g. for small superficial previously debrided wounds

Apply non-stick material e.g. Bactigras

Apply 3-5 layers of dry material e.g. gauze

Cover with crepe bandage

Change after 3days & then daily up to day 21. If there is no healing, consider skin grafting.

Silver sulfadiazine/transparent polythene bags for hands

Skin grafting e.g. for frictional burns.

Indications for occlusive dressing

• -If the burn is oozing too much
• -If there is a risk of infection
• -Children
• -If co-morbid conditions present
• -Joints
• -Patient's comfort

Skin grafting

If wounds don’t heal between 21-30 days. Skin graft immediately for a frictional burn. It encourages healing.

Graft-any tissue removed from one anatomical part of the body to the recipient floor and its survival depends on the floor. (blood transfusion is not a  graft)

Flap-(Pediculated graft) –removed with own blood supply.

Any part of the body can donate except the perineum and below the eyes.

Skin graft types: Spit thickness and Full-thickness grafts

1st 24 hours –graft survives by osmosis

Next 48 hours Neovascularization.Beyond its take or non-take (rejected)

The donor site kept dressed for 10-14 days.

Grafting across joints should apply splints to facilitate take

Biological dressing

-Amniotic membrane

-A graft from mother allograft which is rejected in 2 weeks but left in situ as a biological graft.

Other considerations;

Face burns

Intubate patient & do temporary tarsorrhaphy (suturing eyelids together).

Whistling and blowing mouth for physiotherapy

In neck burns

A pillow is placed under the patients head to hyperextend the neck

The pillow below  the shoulders to prevent contractures

Chest wall burns

2nd and 3rd-degree burns  do occlusive dressing

Do escharotomy for any scar constricting respiratory movements-Do a checker-box release

Upper limb burns

Should be nursed elevated at 45° to reduce edema

Escharotomy lateral and medial also in the web spaces

Patient on a bed with a pillow between his shoulders to carbonic anhydrase inhibition causing metabolic acidosis; sulfonamide sensitivity rash

Start physiotherapy from the day after escharotomy- do it 5 times a week. At night do nocturnal splinting and for sleep comfort and avoid contractures

Lower limbs

Encourage movements to avoid DVT.

NB If  ≥80% TBSA - Supervised Neglect

Investigations in the first 48 hours

1. Full hemogram for Hb determination
2. Blood group and cross-matching if HB <10g/dl
3. Urea and electrolyte levels
4. Creatinine  and renal function and any electrolyte derangement
5. Blood Gas analysis and carboxyhemoglobin if an inhalational burn
6. Input/output chart

Nutritional support

Curreri formula - 25KCal/Kg + (40KCal * %TBSA)

Because burn injury causes a hypermetabolic state that is characterized by a dramatic increase in resting energy expenditure, nutritional support is essential, especially via the enteral route, to reduce intestinal villous atrophy

48 hours - 6 months Management is based on complication control

Escharotomies

Surgical division of constricting eschars (scab formed especially after a burn).

Indications;

• 3rd & 4th Degree Burns
• Circumferential burns - may compromise distal extremity blood flow. Performed on the mid-lateral or medial aspects of limbs, chest burns that would impair respiration

Escharectomy

Surgical –Tangential excision

Medical –Use of mafenide, soaking with NS

After 6months - Reconstructive surgery, Training & Rehabilitation

Physiotherapy - Splint at night & Motion during the day

• To control pain
• Reduce edema & swelling
• To protect the wound
• To minimize cosmetic defects
• To maximize the patient's function

Occupational therapy - To rehabilitate the patient back into a functional living

Psychiatric rehabilitation

Complications of burns

Instant complications

1. Inhalational injury
2. Dehydration

Immediate-hours

1.Hemorrhage

2.Airway obstruction

3.Circulatory collapse

Early complications-days

1. Anemia
2. Hemorrhage (Wound, gastrointestinal bleeding)
3. Thermal injury to red blood cells
4. Bone marrow depression-by the cytokines or by the drugs given.
5. Malnutrition

1 month - 1year

Hypertrophic scars which are itchy, Hyperaemic, and uncomfortable.

Over 1 year

Keloids. A keloid is a true tumor arising from the connective tissue elements of the dermis. keloids grow beyond the margins of the original injury or scar; in some instances, they may grow to enormous size.

Management is by local injection of Steroids & Bleomycin, Excision & Superficial irradiation

Contractures

10 years

Marjolin's ulcer developing in the old burn site

 Systemic Complications

Fluid and electrolyte imbalances

Severe burns decrease sodium in circulation but total body sodium is increased.

Hyperkalemia

Shock, dehydration due to increased fluid loss

Infection;

0-7 days - Contamination

>7 days – Sepsis

GIT;

1. Burns secondary  to swallowing corrosive substances heal by fibrosis with the formation of strictures in esophagus Contractures of the esophagus lead to the obliteration of the angle of HIS, GERD  more acid irritation & burns  which cause more scarring & contractures

Nissen fundoplication is done to break the cycle.

2. Curling's ulcers may cause GIT bleeding

3.Pseudo-intestinal obstruction (paralytic ileus) on the third to the fourth day

4. Diarrhoea secondary to Ileal atrophy in the 7th-8th day; Diarrhoea may also be due to the drugs

5.  Pancreatitis

6. Acalculous cholecystitis

7. Ogilvie's syndrome

Respiratory

• Inhalation burns, edema acute airway obstruction.
• Acute respiratory distress syndrome
• Noxious gases such as carbon monoxide.
• Inhalational burns with atelectasis
• Pneumostatic pneumonia

Genitourinary

• Renal failure evidenced by decreased urine output to less than 400ml/day. This may need dialysis and if not performed, Hepatorenal syndrome may occur.
• Urethral strictures

Skin

• Hypertrophic scars
• Keloids
• Squamous cell carcinoma-Marjolins ulcer

Musculoskeletal

• Contracture formation with limitation of movement
• Deep vein thrombosis and you treat it with anticoagulants
• Electrical burns cause myonecrosis to lead to the loss of a group of muscles or even lead to amputation.

Eye

• Iridocyclitis
• Perforation of the globe
• Lid deformities and exposure keratitis in ectropion
• Cataracts

Hematological

1. Anemia.
2. 1.Hemorrhage (Wound, GIT).
3. 2.Thermal injury to RBCs.
4. Bone marrow depression-by the cytokines or by the drugs given.
5. 4.Malnutrition.
6. 5.Helminthiasis.

All burn patients put on haematinic and anti-helminth drugs.

Other hematological complications- Leucopenia and thrombocytopenia, DIC.

 Multiple organ failure

• Renal failure
• Bleeding from orifices
• Respiratory problems
• Cardiac arrest
• Malnutrition

CNS

• Psychiatric disturbances
• Seizure electrolyte imbalances

CVS-Shock, Arrhythmia, tachycardia, Cardiac arrest.

Factors Affecting Burn Mortality

1.Patient's age

2. Pre-existing medical conditions e.g. Cardiac, Pulmonary, Renal dysfunction

3.Presence of Inhalational injury

3.Size and Depth of Burn

4.Concomitant Injuries

5.Etiology of burn