Corrosive Poisoning - 5 Mark Answer (Forensic Medicine)

Definition

Classification of Corrosive Poisons

I. Corrosive Acids

• Sulphuric acid (H2SO4) - Oil of Vitriol
• Hydrochloric acid (HCl) - Muriatic acid
• Nitric acid (HNO3) - Aqua fortis

• Carbolic acid (Phenol)
• Oxalic acid
• Formic acid

II. Corrosive Alkalis

• Caustic soda (Sodium hydroxide, NaOH)
• Caustic potash (Potassium hydroxide, KOH)
• Ammonia

Mechanism of Action

• Acids: Cause coagulative necrosis - precipitate proteins, abstract water from tissues; produce hard, leathery, firm eschar. The eschar limits depth of penetration somewhat.
• Alkalis: Cause liquefactive (colliquative) necrosis - saponify fats, dissolve proteins; produce soft, gelatinous eschar. Penetrate deeper than acids and cause more extensive damage.

Signs & Symptoms (Clinical Features)

Local Effects:

• Immediate burning pain in the mouth, throat, esophagus, and stomach
• Stains and burns around the lips and mouth (pathognomonic)
• Excessive salivation, nausea, vomiting
• Dysphagia (difficulty swallowing)
• Swollen, edematous mucous membranes

Stains produced (important for exams):

General (Systemic) Effects:

• Intense shock (due to pain and fluid loss)
• Tachycardia, cold and clammy skin
• Oliguria or anuria (renal failure)
• Respiratory distress (if inhaled vapors)
• Convulsions, coma, death

In Alkali Poisoning specifically:

• Soapy feel in the mouth
• Mucous membranes appear whitish and swollen
• Vomitus is soapy and slippery

Postmortem Appearances (PM Findings)

• External: Corrosive stains around mouth, lips, chin; hands (if self-administered)
• Esophagus & Stomach: Mucosa is shrunken, hardened, leathery (acids) or softened/gelatinous (alkalis); hemorrhagic areas; perforation may occur
• Stomach: Contents may be brown (H2SO4) or yellow (HNO3)
• Blood: Often dark, viscid, and altered
• Kidneys: May show tubular necrosis (especially oxalic acid - calcium oxalate crystals)
• Generalized congestion of organs

Treatment / Management

1. Do NOT induce vomiting (re-exposure of esophagus)
2. Do NOT use chemical antidotes (heat produced by neutralization worsens burns)
3. Dilution - Large quantities of water or milk immediately
4. Treat shock: IV fluids, analgesics
5. Gastric lavage only if within 30-60 minutes and no perforation
6. Specific antidotes:
   • For acid poisoning: Milk of magnesia, aluminum hydroxide gel, soap solution
   • For alkali poisoning: Dilute vinegar (1%), dilute citric acid or lemon juice
7. Treat complications: perforation, stricture, renal failure
8. Long-term: Esophageal dilatation for post-corrosive stricture

Medicolegal Importance

1. Manner of death: Mostly accidental (household chemicals); suicidal (especially carbolic acid); rarely homicidal
2. Vitriolage: Throwing of acid on a person - a specific offense under IPC; H2SO4 most commonly used
3. Cause of death: Circulatory collapse (immediate), perforation of stomach/esophagus (24-48 hrs), septicemia/renal failure (delayed), aspiration pneumonia
4. Chemical analysis: Gastric contents and viscera sent for chemical examination
5. Important note: Corrosive marks may be mistaken for postmortem artifacts or burns; history and pattern of staining help differentiate

Important Exam Points to Remember

• Alkalis are MORE dangerous than acids (deeper penetration due to liquefactive necrosis)
• Nitric acid gives yellow stain (xanthoprotein reaction - classic MCQ)
• Sulphuric acid causes black charring
• Oxalic acid is unique: causes hypocalcemia, calcium oxalate crystals in kidneys
• Carbolic acid (phenol): urine turns green to black on exposure to air (carboluria); distinctive carbolic smell
• Chemical antidotes are CONTRAINDICATED (neutralization generates heat)
• Vitriolage (acid throwing) is a specific medicolegal term - most commonly H2SO4

Reference: The Essentials of Forensic Medicine & Toxicology - Dr. K.S. Narayan Reddy & Dr. O.P. Murthy, Chapter 26: Corrosive Poisons, Section II - Toxicology.