Aluminium phosphide poisoning for md emergency medicine final exam
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"aluminium phosphide" poisoning management
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PMID: 42454906
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Aluminium Phosphide (ALP) Poisoning - MD Emergency Medicine Final Exam
Overview / Medicolegal Importance
Aluminium phosphide (ALP) is a solid fumigant pesticide, insecticide, and rodenticide widely used for grain preservation. It is sold under trade names: Celphos, Alphos, Quickphos, Phostoxin, Phosphotex, Fumigran. It is cheap, easily available, and highly lethal - often called "the agent of sure death."
- Tablet composition: 3 g grey-green tablet; 56% active ingredient; mixed with urea and ammonium carbonate
- Each tablet releases: 1 g of phosphine (PH3) gas
- India: Highly prevalent in Haryana, Punjab, UP, Rajasthan - common suicidal and homicidal agent (used in dowry deaths in rural areas)
- Medicolegal significance: Suicidal >> Accidental > Homicidal
Chemical Reaction - Mechanism of Gas Liberation
ALP + 3H₂O → Al(OH)₃ + PH₃ (Phosphine)
- Reaction is accelerated by HCl in the stomach
- On ingestion, contact with gastric juice liberates phosphine gas rapidly
- On inhalation, direct pulmonary absorption occurs
Mechanism of Toxicity
Phosphine is a systemic cellular poison:
- Inhibits cytochrome c oxidase (Complex IV of the mitochondrial electron transport chain) - the primary mechanism
- Blocks oxidative phosphorylation → cellular hypoxia
- Generates reactive oxygen species (ROS) - free radical injury to cell membranes
- Inhibits catalase and other antioxidant enzymes
- Affects all organs - heart, lung, liver, kidney, CNS
Key point for exam: Phosphine toxicity = mitochondrial cytochrome oxidase inhibition + oxidative stress
Toxicokinetics
| Parameter | Detail |
|---|---|
| Fatal dose | 1-3 g (1-3 tablets); 1-2 g lethal |
| Inhalation fatal conc. | 400-600 ppm within 1 hour; >0.3 ppm causes severe illness |
| Fatal period | 6-12 hours; majority of deaths within 24 hours |
| Absorption | Rapid from GIT by simple diffusion; also from lungs after inhalation |
| Metabolism | Metabolized in liver; phosphine slowly released (prolonging symptoms) |
| Excretion | Oxidized to oxyacids → excreted as hypophosphite in urine; also excreted unchanged through lungs |
Clinical Features
By Severity
Mild (inhalation):
- Mucous membrane irritation
- Dizziness, fatigue, headache
- Tightness in chest, nausea, vomiting, diarrhea
Moderate:
- Ataxia, numbness, paresthesia
- Tremors, diplopia
- Jaundice, muscular weakness, incoordination, paralysis
Severe (ingestion - systemic):
| System | Features |
|---|---|
| GIT | Nausea, vomiting, diarrhea, retrosternal/epigastric burning pain |
| CVS | Hypotension, cardiogenic shock (most common cause of death), arrhythmias, myocarditis, pericarditis, acute CCF |
| Respiratory | Cough, dyspnea, cyanosis, pulmonary edema, ARDS, respiratory failure |
| CNS | Headache, restlessness, excitement, agitation, convulsions, acute hypoxic encephalopathy, coma |
| Renal | Oliguria, acute renal failure |
| Hepatic | Jaundice, hepatitis, hepatomegaly |
| Metabolic | Metabolic acidosis, hypocalcemia (tetany), hypomagnesemia |
Pathognomonic feature: Garlicky/fishy odour from breath and vomitus
ECG abnormalities: Sinus tachycardia, bradycardia, heart block, various arrhythmias
Major complications:
- Pericarditis
- Acute massive GI bleeding
- ARDS
- Acute CCF
Mortality: Extremely high - 35% to 100% (one of the highest among poisonings). Cardiogenic shock is the most common cause of death.
Investigations
Bedside/Clinical Chemical Tests
Test 1 - Silver Nitrate Breath Test (most important):
- Filter paper impregnated with 0.1 N silver nitrate used as a face mask
- Patient breathes in and out for 5-10 minutes
- Paper turns BLACK if phosphine is present (AgNO₃ reduced to metallic Ag by PH₃)
Test 2 - Gastric Aspirate Test:
- Mix 5 mL gastric aspirate + 15 mL water in a flask
- Cover mouth with AgNO₃-impregnated filter paper
- Heat at 50°C for 15-20 minutes
- Paper turns black = phosphine confirmed
Laboratory Workup (for management)
- ABG (metabolic acidosis, hypoxia)
- Serum electrolytes (hypomagnesemia, hypocalcemia, hypokalemia)
- Serum bicarbonate
- ECG / cardiac monitoring
- LFT, RFT
- CBC, coagulation profile
Management
A. Decontamination
No specific antidote exists for ALP poisoning.
Gastric lavage:
- Done after endotracheal intubation (to protect airway)
- Lavage with potassium permanganate (oxidizes phosphine to nontoxic phosphate) - repeat 2-3 times
- Alternatively: 3-5% sodium bicarbonate, 1% copper sulphate, or mineral oil
- Controversy: Recent studies suggest gastric lavage may worsen outcome (more moisture = more phosphine release); some advocate against it
- Activated charcoal: 100 g orally mixed with sorbitol (NOT water - water accelerates PH₃ release) - 240 mL per 30 g charcoal
- Antacids: Reduce GI symptoms and absorption
- Liquid paraffin: Given to aid excretion of ALP and phosphine from gut
B. Antiarrhythmic / Cardiac
Magnesium sulphate - cornerstone of treatment:
- Reduces organ toxicity
- Corrects hypomagnesemia and arrhythmias
- Dose (Dikshit): 3 g IV bolus → 6 g over 24 hours for 5-7 days
- Dose (Essentials FMT 2026): 1 g initial → repeated for next 2 hours → 1-1.5 g every 6 hours for 5-7 days as continuous IV infusion
- Calcium salts IV for hypocalcemia/tetany
C. Shock Management
- IV fluids: 4-6 liters during first 3-6 hours; 50% as normal saline
- Low-dose dopamine: 4-6 mcg/kg/min (inotropic support)
- IV hydrocortisone: 400 mg every 4-6 hours - highly effective; reduces dopamine requirement
- Steroids also combat pulmonary edema
D. Metabolic Acidosis
- IV sodium bicarbonate 50 mEq every 15 minutes until arterial bicarbonate >15 mmol/L
E. Respiratory Support
- Oxygen supplementation
- Endotracheal intubation and mechanical ventilation for respiratory failure/ARDS
F. Renal Support
- Peritoneal dialysis or hemodialysis for renal failure (also useful for metabolic acidosis)
G. Antioxidant Therapy (Emerging / Evidence-Based)
Per 2026 review in Xenobiotica (PMID 42454906) and Rosen's Emergency Medicine:
- N-acetylcysteine (NAC) IV - limited but beneficial evidence
- Vitamin E - antioxidant
- Melatonin - antioxidant
- Magnesium - antioxidant + anti-arrhythmic
- Rationale: Phosphine causes massive ROS generation; antioxidant therapy addresses this mechanism
H. Antibiotics
For secondary infections
Summary of Treatment Protocol (Exam Mnemonic: "No GMLADS")
| Letter | Step |
|---|---|
| N | No specific antidote |
| G | Gastric lavage (KMnO₄, post-intubation) + activated charcoal in sorbitol |
| M | Magnesium sulphate (anti-arrhythmic, organ-protective) |
| L | Liquid paraffin + IV fluids for shock |
| A | Antioxidants (NAC, Vit E, melatonin) |
| D | Dopamine (low-dose) + steroids (hydrocortisone) |
| S | Sodium bicarbonate (acidosis), Supportive O₂/ventilation |
Postmortem Appearances
- Garlic-like odour at mouth, nostrils, gastric contents (pathognomonic)
- Blood-stained froth at mouth and nostrils
- Congested mucous membrane of lower esophagus, stomach, and duodenum (see image below)
- Decreasing congestion in small intestine (gradient)
- Lungs, liver, spleen, kidneys, brain - all congested
- Centrizonal hemorrhagic necrosis of liver
Histopathology
| Organ | Finding |
|---|---|
| Stomach | Congestion, edema, leucocytic infiltration, sloughing of gastric mucosa |
| Lungs | Congestion, edema, desquamation of respiratory epithelium, thickened alveoli, lymphocytic infiltration |
| Kidneys | Congestion, necrosis, tubular degeneration and regeneration |
| Adrenals | Congestion, hemorrhage, necrosis, lipid depletion in cortex |
| Heart | Congestion, edema, fragmentation of fibers, focal necrosis, leucocytic infiltration |
| Brain | Congestion, edema |
High-Yield Exam Points Summary
| Fact | Value |
|---|---|
| Trade names | Celphos, Alphos, Quickphos, Phostoxin, Phosphotex |
| Chemical reaction | ALP + 3H₂O → Al(OH)₃ + PH₃ |
| Fatal dose | 1-3 tablets (1-3 g) |
| Fatal period | 6-12 hours (most deaths in 24 hrs) |
| Odour | Garlicky/fishy |
| Primary mechanism | Cytochrome oxidase inhibition + ROS generation |
| Most common cause of death | Cardiogenic shock |
| Specific antidote | NONE |
| Chemical test | 0.1 N silver nitrate paper - turns BLACK |
| Gastric lavage solution | KMnO₄ (oxidizes to phosphate) |
| Charcoal mixed in | Sorbitol (NOT water) |
| Key antiarrhythmic | Magnesium sulphate |
| Inotrope of choice | Dopamine (low-dose 4-6 mcg/kg/min) |
| Steroid dose | Hydrocortisone 400 mg q4-6h |
| Postmortem odour | Garlic at mouth/nostrils/stomach |
| Liver finding | Centrizonal hemorrhagic necrosis |
| Mortality | 35-100% |
Sources: The Essentials of Forensic Medicine and Toxicology, 36th ed. (2026); P C Dikshit Textbook of Forensic Medicine and Toxicology; Rosen's Emergency Medicine, 9th ed.; Aghebat-Bekheir et al., Xenobiotica 2026 (PMID 42454906) - most recent review confirming antioxidant therapy and supportive care as mainstay.
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