What is the recommended management, including lethal dose, for a patient who has ingested aluminium phosphide (Celphos)?

Management of Aluminum Phosphide (Celphos) Poisoning

Aluminum phosphide poisoning is a medical emergency with mortality exceeding 70%, requiring immediate ICU-level care for all exposures, as ingestion of as little as 150-500 mg can be fatal. 1

Lethal Dose and Toxicity

• The lethal dose is 150-500 mg of aluminum phosphide, which corresponds to approximately 1-3 tablets, as each tablet typically contains 56% aluminum phosphide (approximately 500-600 mg per 1g tablet). 1
• Toxicity results from phosphine gas released when aluminum phosphide contacts moisture in the gastrointestinal tract, causing mitochondrial dysfunction, free radical generation, and multi-organ failure. 2
• Mortality rates exceed 70% even with aggressive treatment, with circulatory failure and severe hypotension being the most common causes of death. 2

Immediate Safety Measures

Healthcare Worker Protection (CRITICAL FIRST STEP)

• All healthcare personnel must wear full-face gas masks and butyl rubber gloves before any patient contact—ordinary surgical masks and latex gloves do not protect against phosphine vapor. 3
• Never initiate patient care without proper personal protective equipment, as secondary phosphine exposure has caused severe illness requiring ICU admission, atropine, pralidoxime, and prolonged intubation in healthcare workers. 3, 1
• Remove contaminated clothing immediately outside the hospital to prevent vapor generation inside the facility. 3
• Ensure treatment areas are well-ventilated, as poorly ventilated spaces have resulted in healthcare worker poisoning requiring intensive interventions. 3, 1

Gastrointestinal Decontamination

• Perform extensive gastric lavage with a mixture of coconut oil and sodium bicarbonate solution as soon as possible after presentation. 4, 5
• Coconut oil may prevent further absorption of aluminum phosphide and has shown positive clinical significance in case reports of survival after lethal dose ingestion. 4
• Activated charcoal can be considered for gastrointestinal decontamination, although its ability to adsorb phosphine gas is uncertain. 1
• Administer oral sodium bicarbonate and sorbitol suspension following gastric lavage. 4

Cardiovascular Support

• Initiate aggressive fluid resuscitation and vasopressor support immediately for the near-universal hypotension and circulatory failure. 6, 1
• Noradrenaline and dopamine infusions should be started for hypotension and titrated to maintain adequate perfusion. 7
• Administer calcium gluconate (100-200 mg/kg/dose) via slow IV infusion with continuous ECG monitoring for life-threatening arrhythmias and cardiac membrane stabilization. 1
• Do not administer sodium bicarbonate and calcium through the same IV line to avoid precipitation. 1
• Continuous cardiac monitoring is mandatory, as cardiotoxicity including atrial fibrillation, ST elevation, and myocardial infarction can develop hours after ingestion. 8

Respiratory Management

• Administer 100% oxygen immediately via high-flow mask or endotracheal tube to all suspected cases while awaiting confirmation. 3
• Continue high-flow oxygen until metabolic acidosis resolves and respiratory symptoms improve. 3
• Intubate patients with respiratory distress or loss of consciousness using low tidal-volume ventilation (≤6 mL/kg ideal body weight) with moderate PEEP. 3
• Target normoventilation with arterial PaCO₂ of 5.0-5.5 kPa—avoid hyperventilation because it worsens tissue perfusion and increases mortality. 3
• CPAP may be considered only for conscious, cooperative patients without contraindications such as full stomach or bowel paralysis. 3, 1

Metabolic Acidosis Management

• Administer sodium bicarbonate (1-2 mEq/kg IV push) for severe metabolic acidosis, which is a near-universal finding in aluminum phosphide poisoning. 1, 4, 7
• Continue IV sodium bicarbonate infusion as needed to maintain pH >7.2, guided by serial arterial blood gas measurements. 4, 7

Magnesium Sulfate Administration

• Administer intravenous magnesium sulfate to reduce cardiac arrhythmias and mortality, though there is no uniformity in dosing worldwide. 8, 4
• Magnesium sulfate has well-documented benefit in reducing arrhythmias associated with aluminum phosphide poisoning. 8

Renal Replacement Therapy

• Consider hemodialysis for severe poisoning, particularly when metabolic acidosis is refractory to bicarbonate therapy or multi-organ failure develops. 7
• Hemodialysis contributed to symptomatic treatment and survival in documented cases of cardiac arrest from aluminum phosphide poisoning. 7
• High-flux dialysis membranes are preferred if aluminum toxicity is suspected. 1

Management of Aluminum Toxicity (If Suspected)

• Measure serum aluminum levels if aluminum toxicity is suspected, particularly in patients requiring prolonged intensive care. 1
• For serum aluminum levels between 60-200 µg/L, administer deferoxamine (DFO) at 5 mg/kg intravenously with careful monitoring, using high-flux dialysis membranes to enhance clearance of aluminum-DFO complexes. 1
• For serum aluminum levels >200 µg/L, deferoxamine must be withheld due to high risk of precipitating acute aluminum neurotoxicity; instead, initiate intensive high-flux hemodialysis daily for 4-6 weeks until levels decline. 9, 1
• Fatal mucormycosis can occur with DFO therapy, with 91% mortality in dialysis patients, so reduced dosing and expanded intervals minimize this risk. 1

Monitoring and Complications

• Observe for delayed neuromuscular weakness that may appear up to four days after exposure, potentially necessitating prolonged ventilatory support. 3
• Screen for rhabdomyolysis by tracking creatine kinase and potassium levels, as calcium-mediated myonecrosis can lead to respiratory muscle weakness. 3, 1
• Monitor for multi-organ failure including hepatic injury, acute renal failure, and acute respiratory distress syndrome. 2, 4
• Serial ECGs and cardiac troponin levels should be obtained to detect evolving cardiotoxicity. 8

Critical Pitfalls to Avoid

• Hyperventilation strategies must be avoided because they exacerbate tissue hypoxia and increase mortality. 3
• Avoid physical restraints without adequate sedation, as this can worsen outcomes. 1
• Avoid succinylcholine or mivacurium for intubation if cholinesterase inhibition is suspected. 1
• Do not use aluminum hydroxide as a phosphate binder for more than 1-2 days to avoid cumulative aluminum toxicity. 1
• Hyperbaric oxygen therapy has no role in aluminum phosphide poisoning and is contraindicated due to hemodynamic instability and the need for continuous bedside intensive care. 6

Prognosis

• Despite aggressive supportive care, mortality remains extremely high at 70% or greater. 2
• Survival rates of 42% have been reported with the comprehensive treatment regimen including coconut oil gastric lavage, aggressive cardiovascular support, and hemodialysis. 5
• Early presentation and rapid initiation of treatment improve survival, though even patients presenting within 6 hours can develop fatal complications. 8, 4