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Burns - Complete MBBS Guide

From Basic Science to Clinical Management

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1. ANATOMY RELEVANT TO BURNS

• Epidermis - avascular, composed of stratified squamous epithelium (keratinocytes). Regeneration occurs from the basal layer and skin appendages (hair follicles, sweat glands).
• Dermis - vascular, contains collagen, elastin, sweat glands, sebaceous glands, and hair follicles. Divided into:
  • Papillary dermis (superficial) - thin, loosely organized
  • Reticular dermis (deep) - thick, densely organized
• Subcutaneous tissue (hypodermis) - fat and connective tissue
• Deep structures - fascia, muscle, periosteum, bone

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2. DEFINITION & ETIOLOGY

• Thermal - flame, scalds (hot liquids/steam), contact with hot objects
• Chemical - acids (coagulation necrosis), alkalis (liquefaction necrosis - deeper, more dangerous)
• Electrical - low voltage (<1000V) or high voltage (>1000V); injury follows path of least resistance (nerves, blood vessels)
• Radiation - UV light (sunburn), ionizing radiation
• Friction - road rash, abrasion burns

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3. BURN DEPTH CLASSIFICATION

From Schwartz's Surgery 11e: "Burn wounds are commonly classified as superficial (first-degree), partial-thickness (second-degree), full-thickness (third-degree), and fourth-degree based on the original burn depth classification by Dupuytren in 1832."

From Tintinalli's Emergency Medicine: Deep partial-thickness burns "extend into the deep dermis (reticular layer). Hair follicles and sweat and sebaceous glands are damaged, but their deeper portions usually survive. Hot liquids (e.g., oil or grease), steam, or flame usually cause this type of injury. The burned area does not blanch; it has absent capillary refill and absent pain sensation."

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4. ESTIMATING BURN AREA - TBSA (Total Body Surface Area)

Rule of Nines (Wallace's Rule of Nines) - Adults

Lund and Browder Chart

• More accurate than Rule of Nines, especially in children, because it accounts for age-related changes (head larger, legs smaller in infants).
• From Sabiston Surgery: The Berkow Formula (similar principle) adjusts head from 19% at birth to 7% in adults, and thighs from 5.5% at birth to 9.5% in adults.

Palmar Method

• Patient's palm (including fingers) = approximately 1% TBSA - useful for patchy/scattered burns.

Galveston Formula (Children)

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5. BURN SEVERITY CLASSIFICATION (ABA - American Burn Association)

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6. PATHOPHYSIOLOGY

Local Response - Jackson's Zones of Burns (1953)

1. Zone of Coagulation (center) - irreversible cell death, no blood flow, no viable tissue
2. Zone of Stasis - potentially viable tissue with decreased perfusion; can be salvaged or may progress to necrosis if not resuscitated properly
3. Zone of Hyperemia (periphery) - vasodilatation, increased blood flow, fully recovers

Clinical implication: Aggressive fluid resuscitation is aimed at preserving the zone of stasis.

Systemic Response

• Fluid shifts from intravascular to interstitial (burn edema) due to release of inflammatory mediators (histamine, prostaglandins, bradykinin, oxygen free radicals)
• Decreased cardiac output, increased peripheral vascular resistance
• "Burn shock" - distributive + hypovolemic

• Basal metabolic rate increases up to 200% (Schwartz's Surgery 11e)
• Marked protein catabolism and muscle wasting
• Hyperglycemia common, insulin resistance
• Persistent for months after injury

• Skin barrier disruption leads to infection risk
• Systemic immunosuppression
• Increased susceptibility to sepsis

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7. INITIAL EVALUATION AND EMERGENCY MANAGEMENT

Primary Survey (ABCDE)

• Most critical priority. Inhalation injury can cause rapid, severe airway edema.
• Warning signs: hoarse voice, stridor, wheezing, subjective dyspnea, oropharyngeal mucosal burns
• From Schwartz's 11e: "Perioral burns and singed nasal hairs alone do not indicate upper airway injury, but are signs that the oral cavity and pharynx should be evaluated for mucosal injury."
• Early elective orotracheal intubation if any concern - do not wait for complete obstruction

• 100% oxygen via non-rebreather mask for all burn patients
• Mandatory for CO poisoning treatment
• Check for circumferential chest burns - may need escharotomy

• IV access (2 large-bore IVs, preferably through unburned skin)
• Start fluid resuscitation
• Estimate TBSA and begin Parkland formula

• Neurological status, screen for CO/cyanide poisoning

• Remove all clothing and jewelry
• Stop the burning process (cool water for 20 minutes for thermal burns)
• Prevent hypothermia (especially in children)

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8. INHALATION INJURY

Three Types:

1. Upper airway (supraglottic) injury - direct thermal injury; causes edema and obstruction
2. Lower airway (infraglottic) injury - chemical injury from toxic combustion products; causes tracheobronchitis, bronchospasm, mucosal sloughing
3. Systemic toxin injury - CO and cyanide poisoning

Carbon Monoxide (CO) Poisoning

• CO has 200-250x greater affinity for hemoglobin than oxygen (forms carboxyhemoglobin)
• Also inhibits cytochrome oxidase (mitochondrial toxicity), uncouples oxidative phosphorylation
• Pulse oximetry is falsely normal - must check arterial blood gas with co-oximetry
• Symptoms: headache, confusion, coma, cardiac arrhythmias
• Treatment: 100% normobaric O₂ (reduces CO half-life from 250 minutes to 40-60 minutes)
• Hyperbaric O₂: controversial; logistically difficult in major burns

Cyanide Poisoning (from burning plastics, synthetics)

• Inhibits cytochrome c oxidase - blocks oxidative phosphorylation
• Features: severe lactic acidosis, neurological symptoms, pulmonary edema, ST changes on ECG
• Classic signs (bitter almond breath, cherry-red skin) are unreliable - do not rely on them
• Treatment: Hydroxocobalamin (first-line, rapidly complexes with cyanide) + sodium thiosulfate + 100% O₂

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9. FLUID RESUSCITATION

Parkland Formula (Baxter Formula) - Most Widely Used

• Fluid type: Lactated Ringer's (Normal Saline acceptable)
• Half (50%) given in first 8 hours from time of injury (not time of arrival!)
• Remaining half given over next 16 hours
• In children <2 years: 5% dextrose in LR (to prevent hypoglycemia)

• Total = 4 × 70 × 40 = 11,200 mL over 24 hours
• First 8 hours: 5,600 mL (or ~700 mL/hr)
• Next 16 hours: 5,600 mL (or ~350 mL/hr)

From Tintinalli's EM: "Fluid resuscitation guided by the Parkland formula is only a rough starting point...monitor and adjust according to individual patient response."

Modified Brooke Formula (ABA Consensus Formula)

• 2-3 mL × kg × %TBSA of LR in first 24 hours (less fluid, reduce "fluid creep")
• Increasingly preferred

Monitoring Adequacy of Resuscitation

• Urine output is the gold standard endpoint:
  • Adults: 0.5 mL/kg/hr (30-50 mL/hr)
  • Children: 1 mL/kg/hr
• Other markers: Blood pressure, heart rate, mental status, lactate clearance

"Fluid Creep"

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10. WOUND CARE & DRESSINGS

First Aid

• Cool running water for 20 minutes (not ice water - causes vasoconstriction and hypothermia)
• Remove clothing, rings, and constricting items

Wound Cleaning

• Gentle cleaning with chlorhexidine or dilute povidone-iodine
• Blister management: small intact blisters may be left; large blisters or those over joints are typically deroofed

Topical Antimicrobials

Modern Wound Dressings

• Biological dressings: cadaveric allograft (gold standard temporary cover), xenograft (porcine skin)
• Biosynthetic: Biobrane, Integra (dermal regeneration template)
• Silver-impregnated dressings: Mepilex Ag, Aquacel Ag

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11. ESCHAROTOMY

• Extremity compartment syndrome (tense swelling, absent pulses, pallor, pain on passive stretch)
• Chest: inadequate ventilation due to restricted chest wall expansion

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12. SURGICAL MANAGEMENT

Early Excision and Grafting

• Modern standard of care for deep partial-thickness and full-thickness burns
• Early tangential excision (within 48-72 hours) improves outcomes: reduced infection, reduced hospital stay, reduced mortality
• Split-thickness skin graft (STSG) is the standard coverage
  • Donor site: thighs, back, scalp
  • Meshed grafts expand coverage; meshing ratio typically 1:1.5 to 1:4

Wound Coverage Options

1. Autograft (patient's own skin) - definitive, permanent
2. Allograft (cadaveric skin) - temporary biological dressing, immunologically rejected in 2-3 weeks
3. Xenograft (porcine skin) - temporary biological dressing
4. Cultured Epithelial Autograft (CEA) - cultured from patient's own keratinocytes; used for massive burns where donor sites are limited
5. Integra (artificial dermis) - bovine collagen + chondroitin sulfate matrix covered with silicone; two-stage process

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13. BURN INFECTIONS AND SEPSIS

Common Organisms

• Early (<5 days): Gram-positive (S. aureus, Streptococcus)
• Late: Gram-negative (Pseudomonas aeruginosa - most common and feared; Klebsiella, E. coli)
• Fungal: Candida, Aspergillus (especially in prolonged hospitalization)

Diagnosis

• Burn wound biopsy with quantitative culture: >10⁵ organisms/gram of tissue = wound infection
• Systemic signs: fever, tachycardia, leukocytosis - unreliable (common in burns without infection)
• Conversion of partial-thickness to full-thickness wound is a key sign

Systemic sepsis criteria in burns (ABA definition):

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14. COMPLICATIONS OF BURNS

Early Complications

Late Complications

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15. SPECIAL TYPES OF BURNS

Electrical Burns

• Entry and exit wounds - entry usually small, dry, charred; exit wound larger (explosive)
• Deep injury along path of least resistance (nerves, vessels, muscles)
• Massive internal injury with deceptively small surface area
• Cardiac arrhythmias (immediate ECG monitoring mandatory)
• Myoglobinuria - from massive rhabdomyolysis; causes acute kidney injury; treat with:
  • Aggressive IV fluids to maintain urine output 1-2 mL/kg/hr (higher than thermal burns)
  • Urinary alkalinization (sodium bicarbonate)
  • Mannitol
• Cataract - delayed complication of high-voltage electrical burns (especially head and neck entry)
• Tetanic muscle contractions can cause spinal fractures

Chemical Burns

• Acid burns: coagulation necrosis - forms a protective eschar that limits depth
• Alkali burns: liquefaction necrosis - more dangerous, continues to penetrate deeper
• Treatment: Copious irrigation with water (minimum 20-30 minutes) - DO NOT neutralize (exothermic reaction causes additional injury)
• Hydrofluoric acid (HF): unique - forms insoluble calcium salts; causes systemic hypocalcemia → life-threatening cardiac arrhythmias; treat with topical/injected calcium gluconate
• Phenol burns: systemic absorption causes CNS toxicity; dilute with water, use polyethylene glycol
• White phosphorus: spontaneously ignites in air; keep covered with water, remove under water

Radiation Burns

• UV (sunburn): treated as superficial/first-degree burn
• Ionizing radiation: delayed presentation, progressive tissue damage; no standard antidote

Tar/Asphalt Burns

• Cool with cold water immediately
• Remove with lipid-based solvents (e.g., mineral oil, butter) - do NOT pull off hot tar

Scald Burns (Scalds)

• Most common in children and elderly
• Hot liquids: superficial partial-thickness pattern ("splash/drip" pattern)
• Immersion scalds: uniform, stocking/glove distribution - raises suspicion of non-accidental injury (NAI)

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16. NUTRITION IN BURNS

• Metabolic rate increases up to 200% of baseline
• Early enteral nutrition (within 6-12 hours) is the standard: reduces catabolism, lowers infection rate, prevents ileus
• Caloric calculation: Curreri formula = 25 kcal/kg/day + 40 kcal × %TBSA/day
• Protein: 1.5-2.5 g/kg/day
• Glutamine supplementation: reduces infectious complications
• Micronutrients: Vitamins C, E; zinc, selenium, copper support wound healing
• β-blockers (propranolol): attenuate hypermetabolism, reduce heart rate, decrease catabolism - especially in pediatric burns
• Oxandrolone (anabolic steroid): improves lean body mass, reduces length of stay, used in major burns
• Strict glucose control: hyperglycemia worsens outcomes; target 100-150 mg/dL

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17. PROGNOSIS - BAUX SCORE

• Score >100: historically associated with ~50% mortality
• Score >140: very high mortality

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18. BURN CENTER REFERRAL CRITERIA (ABA)

1. Partial-thickness burns >10% TBSA
2. Burns involving face, hands, feet, genitalia, perineum, or major joints
3. Full-thickness (3rd degree) burns at any size
4. Electrical burns (including lightning)
5. Chemical burns
6. Inhalation injury
7. Burns in patients with preexisting medical conditions
8. Burns with concomitant trauma
9. Burns in children at hospitals without pediatric expertise
10. Burns in patients requiring special social/emotional/rehabilitative intervention

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19. PEDIATRIC BURNS - KEY DIFFERENCES

• Head = larger proportion of TBSA (9% at 1 year vs 7% in adult) - adjust with Lund-Browder
• Greater risk of hypothermia (larger surface-to-volume ratio)
• Greater risk of hypoglycemia (use D5LR in children <2 years)
• Galveston formula for fluid resuscitation
• Non-accidental injury (NAI/child abuse) must always be considered:
  • Symmetric stocking/glove scald distribution
  • Delay in seeking treatment
  • History inconsistent with injury pattern
  • Multiple injuries at different stages of healing

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20. REHABILITATION

• Early physiotherapy and splinting to prevent contractures
• Pressure garments: worn 23 hours/day for 12-18 months to reduce hypertrophic scarring
• Silicone gel sheets: reduce scar thickness and erythema
• Laser therapy for scar remodeling
• Psychological support: CBT, EMDR for PTSD
• Contracture release surgery when joints are functionally limited
• Return to work/school as early as possible (most patients recover function)

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QUICK SUMMARY TABLE

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Parkland Formula - Fluid Timing Explained

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The 8 hr + 16 hr Division

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CRITICAL POINT - Most Exam Trap ⚠️

The 8 hours is counted from the TIME OF INJURY, NOT from time of arrival to hospital.

• Patient burns at 2:00 PM
• Arrives at hospital at 4:00 PM (2 hours late)
• The "first 8 hours" deadline is 10:00 PM (not midnight)
• So you only have 6 hours left to give the first half of fluids
• You must increase the rate to compensate for lost time

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Worked Example

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Why This Division?

• Capillary leak is MAXIMAL in the first 8 hours after burn - fluid pours out of vessels into tissues rapidly, requiring fast replacement
• After 8 hours, capillary integrity begins to restore - slower infusion is enough
• After ~24 hours, capillary leak resolves and fluid starts to mobilize back (diuresis phase)

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Monitor and Adjust

• Urine output: 0.5 mL/kg/hr (adults) / 1 mL/kg/hr (children)
• If urine output too low → increase rate
• If urine output too high → decrease rate (avoid fluid creep)

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Patient Arrives 6 Hours After Burn

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Timeline Visualization

Burn happens     Patient arrives     8 hr deadline     24 hr mark
    |                  |                  |                |
  0 hr               6 hr               8 hr            24 hr
    |←── 6 hrs passed──→|←── 2 hrs left ──→|←── 16 hrs ──→|
         (no fluids given)    (give 5600mL)   (give 5600mL)

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What You Do

Period 1 - Only 2 hours left to give first half:

• 5,600 mL ÷ 2 hours = 2,800 mL/hr

Period 2 - Next 16 hours:

• 5,600 mL ÷ 16 hours = 350 mL/hr (normal slower rate)

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Important Rules to Remember

• Pulmonary edema
• Fluid overload signs
• Abdominal compartment syndrome

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Summary Table

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Patient Arrives at 7 hr 45 min After Burn

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The Problem

Burn happens          Patient arrives    8 hr deadline
    |                       |                |
  0 hr                   7hr 45min          8 hr
    |←─── 7hr 45min ───────→|←── 15 min ───→|

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What You Actually Do

The Practical Answer:

Give the entire 24-hour calculated volume (both halves) evenly over the remaining time left in the 24-hour period.

Calculation:

• Time remaining from arrival to 24-hr mark = 24 - 7.75 = 16.25 hours
• Total fluid = 11,200 mL
• Rate = 11,200 ÷ 16.25 = ~689 mL/hr

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Some Textbooks Say It Differently

Give the full 11,200 mL over the next 16 hours (compress the timeline)

• Rate = 11,200 ÷ 16 = 700 mL/hr

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The Underlying Principle

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Most Important Thing to Remember

• Adults: 0.5 mL/kg/hr
• Children: 1 mL/kg/hr

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• Depth classification - know it cold
• Rule of Nines + Lund-Browder for kids
• Parkland formula - calculate in your sleep
• The 8-hr clock starts at injury, not arrival
• Late arrivals - adjust rate or abandon the split
• Always titrate to urine output - the formula is just a guide