Toxicology

Corrosives (Caustics)

Common Corrosives (Caustics)

• Acids
• Inorganic:- Sulphuric, Nitric, Hydrochloric, Chromic,Phosphoric, Boric
• Organic:- Carbolic, Oxalic, Acetic, Formic, Citric
• Alkalis:- Sod./ Pot./ Cal. Hydroxide; Sod./Pot. Carbonate, Ammonia
• Others:- H₂O_2’ Iodine, Pot.permanganate, Quat.ammo. Comp.

Inorganic Acids

• Act on site of application Causing
• Desiccation- Extract water from tissue and liberate heat
• Precipitate protein and coagulation necrosis
• Fix, destroy, and erode tissue
• Convert haemoglobin to haematin
• Formation of eschar

Clinical Effect

• Local application – Chemical burn
• Ingestion
• Chemical burn of lips and area around
• Mucosa of mouth - coagulation necrosis
• Pain in mouth, throat & abdomen
• Features of shock, unable to speak may vomit blood, may be constant retching and eructation

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Management

• Do not give alkali to neutralize acid
• Give milk, egg-white, Boiled rice water
• Supportive measures
• Combat shock
• Parenteral pain killers

Causes of Death

• Early
• Shock, & haemorrhage
• Perforation of stomach & peritonitis
• Oedema of larynx or laryngeal spasm
• Toxaemia
• Delayed
• Renal failure
• Secondary infection & Aspiration pneumonia
• Pyloric stenosis & malnutrition

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Medico-legal aspect

• Accidental- taken in mistake of medicine or alcoholic drink
• Suicidal poisoning- orally taken by people who professionally in contact with acids.
• Homicidal- Vitriolage (By Sulphuric acid)- concentrated acid thrown on face and body to kill or to disfigure especially in sexual jealousy.

Post- Mortem Findings

• Most severe corrosive effect in sulphuric acid followed by nitric acid and mild in hydrochloric acid.
• Teeth may be chalky white in sulphuric a
• Yellowish discolouration in nitric a due to xanthoproteic reaction is distinctive
• Effect on respiratory system more in hydrochloric a as fuming

Individual Acids

• Sulphuric acid (Oil of Vitriol)
• Oily, colourless, heavy, no fumes, Carbonizes blackish eschar. Fatal dose- 5-10 ml
• Nitric acid (Aqua fortis/ Red Spirit of Nitre
• Fuming, causes yellowish discolouration Fatal dose 10-15 ml
• Hydrochloric acid (Muriatic acid, spirit of Salts)
• Yellowish,volatile, fuming, less corrosive, brownish fatal dose 15-20 ml

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Organic Acids- Carbolic Acid

• Also called phenol or phenyl or hydroxy-benzene; the group includes Lysol & dettol
• Used to be very important antiseptic in surgery even now used as disinfectant
• Colourless prismatic needle like crystal turning pink & liquid on exposure to air
• Fatal dose 2 gm crystal or 25-50 ml liquid
• Fatal Period- 3-4 hrs, delayed some days

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Clinical Picture

• Poisoning called Carbolism
• Local effect on application to skin
• Burning pain, numbness, tingling, corrosion & anaesthesia. Eschar (Scab) falls off in a few days leaving brown stained area.
• Systemic effect on oral ingestion
• GIT-
• Nausea, vomiting, burning pain, in chest and abdomen followed by tingling, numbness.

Clinical Picture

• Systemic effect
• Respiration- Slow and laboured
• CNS- Headache, giddiness, convulsion, Coma
• Oliguria & Hepatic faillure
• Hydroquinone & pyrocatechol causes pigmentation of cornea and cartilages - ochronosis
• Carboluria-
• Fresh urine colourless but on exposure to air turns green due to oxidation of metabolites of phenol (hydroquinone & pyrocatechol)

Management

• Oxygen/ Ventilatory Support
• Blood pressure management
• Management of cardiac arrhythmias
• Management of convulsion
• Skin- Wash with undiluted polyethylene Glycol
• Gastric lavage with Mag.sulph/ sod. Sulph
• Treat methaemoglobinaemia by Methylene blue 1-2mg/kg. Exchange transfusion may be needed

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Autopsy Findings

• Smell of Carbolic acid is found in viscera
• Mucosa of stomach is tough grey, corrugated in longitudinal folds & leathery
• Mucosa of mouth, lips, throat, sodden, and ash grey.
• May show corrosion of skin which is initially white but later turns brown
• Urine on exposure to air turns green

Medico-legal aspect

• Occupational hazard and skin of hands usually were affected in surgeons using carbolic acid as antiseptic
• Poisoning is generally accidental, sometimes suicidal and rarely homicidal due to its strong smell

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Oxalic Acid (Ethanedioic Acid, Salt of Sorrel)

• Physical Property:- Colourless, odourless, prismatic crystals with a sour and slightly bitter taste
• Uses:-Bleaching & cleaning agents, ink remover,rust remover, metal polishing
• Industry:- Ceramic, leather, metallurgic, paper, pharmaceutical, & rubber industry

Mechanism of Action

• Local- Corrosive action
• Prolonged contact may cause cyanosis or even gangrene
• Systemic
• Shock
• Hypocalcaemia
• Nephrotoxicity

Clinical Picture

• Fulminating poisoning caused by orally taking of large dose death within minutes
• Acute Poisoning characterized by survival for a few hours in which clinical picture of hypocalcemia manifested.
• Delayed Poisoning due to injury to kidney causing oliguria, haematuria, oxaluria albuminuria & uraemia

Clinical Features

• Yellowish/ whitish corrosion of mucosa with surrounding tissue congestion
• Vomiting mixed with blood (Coffee grounds)
• Signs & symptoms of hypocalcaemia (tetany) as oxalic acid combines with calcium ions.
• Tonic muscle spasms, cramps, & Accoucher’s hand
• +ve Trousseau & Chvostek’s sign
• Pupils usually dilated,
• Metabolic acidosis, renal failure & vent. fibrillation

Diagnosis

• Demonstration of oxalates in Urine
• Low serum calcium but raised oxalates
• Fatal Dose:- 15 to 30 gm of oxalic acid
• Mode of action:- Corrosive action & combining property with serum calcium causing hypocalcaemia & precipitation of oxalates in Liver, Kidneys, heart, lungs and blood
• Fatal period – 1 to 2 hours

Treatment

• Stomach wash with Calcium gluconate or lactate solution also to be left in stomach
• Calcium gluconate I.V. (10 ml 10% soln.) to be repeated
• Dialysis or exchange transfusion for renal failure
• Affected part should be washed with copious water

Autopsy Findings

• Whitish or yellowish corroded areas in GI Tract if taken orally.
• Underlying tissue congested and may be brownish or black
• Crystals of oxalate may be demonstrated in mucosal scrapping
• Altered blood may be present in GI tract

Medico - Legal Importance.

• Majority of cases are accidental and in children
• Poisoning may occur from over eating of plants containing oxalates like- rhubarb leaves, sorrel etc.
• Less frequently used as suicidal poison
• It is rarely used as homicidal poison

Caustic Alkalis

• Ammonia Gas- Smelling Salt
• Ammonium hydroxide- Paint, oil and dirt remover. Refrigerant
• Sod.hydroxide(caustic soda)- Drain cleaner, oven cleaner
• Pot. Hydroxide(caustic potash)- drain cleaner, hearing aid batteries
• Sod. Carbonate- (washing soda)- Household cleaning agent, detergent
• Pot. Carbonate- Household cleaning Agent
• Sod. Hypochlorite- Household bleach

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Clinical Features

• Greyish soapy necrosis of affected skin / mucosa of mouth GI tract due to liquefactive necrosis
• Pain, abdominal ache, tenderness,diarrhoea, tenesmus haematemesis
• Oedema of the pharynx/larynx, glottis requiring emergency tracheostomy
• Injury to eye and respiratory embarrassment and pulmonary oedema in ammonia poisoning

Management

• Removal of the residual poison-washing
• 1-2 glass of milk/ water to dilute
• Watch for complications especially respiratory and manage- Corticosteroid
• Fluid & electrolyte balance
• Endoscopic examination of upper GI tract
• Surgical intervention to prevent/ repair perforation
• Emesis, gastric lavage & acid to neutralise alkali absolutely contraindicated

Medico- Legal points

• Death from caustic alkali is rarely seen
• PM findings are similar but milder than by acids
• Poisoning is mostly accidental and in children in domestic setting
• 10-15 gm/ 15-20 ml Fatal
• Industrial accidental poisoning specially by ammonia often reported

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