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Caustics

• Substances that cause damage on contact with body surfaces
• Degree of injury determined by pH, concentration, volume, duration of contact
• Acidic agents cause coagulative necrosis
• Alkaline agents cause liquefactive necrosis (considered more damaging to most tissues)
• Corrosive agents have reducing, oxidising, denaturing or defatting potential

Alkalis

• Accepts protons → free hydroxide ion, which easily penetrates tissue → cellular destruction
  • Liquefactive necrosis and protein disruption may allow for deep penetration into surrounding tissues
• Examples
  • Sodium hydroxide (NaOH), potassium hydroxide (KOH)
    • Lye present in drain cleaners, hair relaxers, grease remover
  • Bleach (sodium hypochlorite) and Ammonia (NH3)
    • Cleaning products such as oven cleaners, swimming pool chlorinator
    • Household bleach ingestion (4-6% sodium hypochlorite) rarely causes significant esophageal injury

Acids

• Proton donor → free hydrogen ion → cell death via denatured protein → coagulation necrosis and eschar formation, which limits deeper involvement
  • However, due to pylorospasm and pooling of acid, high-grade gastric injuries are common
    • Mortality rate is higher compared to strong alkali ingestions
• Can be systemically absorbed and → metabolic acidosis, hemolysis, AKI
• Examples
  • Hydrochloric acid (HCl), hydrofluoric acid (HF), Sulfuric acid (H2SO4), Phosphoric acid, Oxalic Acid, Acetic acid
    • Found in: auto batteries, drain openers, toilet bowl, metal cleaners, swimming pool cleaners, rust remover, nail primer