Chemical Burns

Introduction & Causative Agents - Skin's Chemical Foes

Chemical burns are tissue injuries from corrosive agents, prevalent in Indian industries like construction (cement), agriculture (fertilizers), textiles, and cleaning.

• Common Causative Agents:
  • Acids: e.g., $H_2SO_4$ (batteries, fertilizers), $HCl$ (metal cleaning). Cause coagulation necrosis.
  • Alkalis: e.g., $NaOH$ (soaps, drain cleaners), $Ca(OH)_2$ (cement, lime). Cause liquefactive necrosis.
  • Organic Solvents: e.g., Phenol (disinfectants), petroleum products (degreasers).
  • Oxidizers: e.g., Bleaches ($NaOCl$), $KMnO_4$.
  • Reducing Agents: e.g., Chromates.

⭐ Alkalis (like cement, drain cleaners) generally cause deeper and more severe burns than acids due to liquefactive necrosis, allowing progressive penetration.

Pathophysiology - How Chemicals Scorch

Chemicals inflict damage via distinct mechanisms:

⭐ Hydrofluoric acid (HF) uniquely causes liquefactive necrosis and binds $Ca^{2+}$ and $Mg^{2+}$, leading to severe pain, bone decalcification, and systemic hypocalcemia/hypomagnesemia.

• Other Notable Agents:
  • White Phosphorus: Combined thermal & chemical injury; ignites with air.
  • Phenols (Carbolic Acid): Coagulative necrosis; potent systemic absorption (CNS, cardiac toxicity).

Clinical Presentation & Diagnosis - Burn Clues & Grades

• General Signs: Pain, erythema, blistering, necrosis.
• Specific Clues (Agent-Dependent):
  • Acids (Coagulative Necrosis):
    • Sulphuric ($H_2SO_4$): Black/brown eschar.
    • Nitric ($HNO_3$): Yellow eschar.
    • Hydrofluoric (HF): Intense pain (often delayed, out of proportion to visible injury), erythema, blistering; risk of systemic hypocalcemia.
    • Phenol (Carbolic Acid): White, then brown eschar; initially painless (local anaesthetic effect).
  • Alkalis (Liquefactive Necrosis): Soapy feel, deep penetration, often more severe than acid burns.
• Burn Depth & TBSA:
  • Classification:
    • Superficial (Epidermal): Erythema, pain, no blisters.
    • Partial-thickness (Dermal): Blisters. Superficial dermal is painful, moist, red, blanches. Deep dermal is less painful, mottled white/pink, may not blanch.
    • Full-thickness: Leathery, dry, insensate; white, charred, or brown.
  • TBSA Estimation (Adult Rule of Nines): Head & Neck 9%, Each Upper Limb 9%, Each Lower Limb 18%, Anterior Trunk 18%, Posterior Trunk 18%, Perineum 1%.
• Diagnosis:
  • History: Identify agent, concentration, volume, duration of contact, irrigation performed.
  • Physical Examination: Assess burn depth, TBSA, signs of systemic toxicity.
  • pH testing (skin/eye): Crucial for unknown agents or alkalis. Irrigate until pH 7.0-7.4.

⭐ Chromic acid burns can cause delayed renal and hepatic failure due to systemic absorption of hexavalent chromium.

Management & Prevention - Dousing the Damage

• Immediate First Aid (ABCDE):
  • Remove contaminated clothing/jewelry.
  • Copious irrigation (water/saline) for at least 30-60 minutes.
  • 📌 DRIP: Decontaminate, Irrigate, Protect, Pain relief.

• Specific Antidotes:
  • Hydrofluoric (HF) Acid: Calcium gluconate.
  • Phenol: Polyethylene glycol (PEG) / Isopropyl alcohol.
  • White Phosphorus: Copper sulfate (1% solution, cautious use, remove particles).
• General Burn Care: Analgesia, non-adherent dressings, tetanus prophylaxis, topical antimicrobials.
• Referral to Burn Unit: Burns >10% TBSA (adults), >5% (children); Full-thickness >2%; Face, hands, feet, genitalia, major joints.
• Prevention: PPE (gloves, goggles), safety protocols, emergency eyewash/shower stations.

⭐ Copious water irrigation is the cornerstone of immediate management for most chemical burns; neutralization attempts without prior copious irrigation can sometimes worsen injury by generating heat.

High‑Yield Points - ⚡ Biggest Takeaways

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