What is the treatment for organophosphate poisoning?

Treatment of Organophosphate Poisoning (Cockroach Killer)

Immediately administer atropine 1-2 mg IV for adults (0.02 mg/kg for children), doubling the dose every 5 minutes until full atropinization is achieved, while simultaneously giving pralidoxime 1-2 g IV followed by continuous infusion, along with decontamination and supportive care. 1

Immediate Decontamination and Safety

• Remove all contaminated clothing and perform copious irrigation with soap and water immediately to prevent ongoing absorption and secondary exposure to healthcare workers 1
• Healthcare providers must wear appropriate personal protective equipment (PPE) when handling contaminated patients or gastric contents, as documented cases show healthcare workers have required atropine, pralidoxime, and even intubation after secondary exposure 1

Atropine Administration - First-Line Life-Saving Treatment

Atropine is the immediate life-saving intervention with Class 1, Level A evidence and should never be delayed 1, 2

Initial Dosing

• Adults: 1-2 mg IV initially (substantially higher than the 0.5-1.0 mg used for bradycardia from other causes) 1, 2
• Children: 0.02 mg/kg IV (minimum 0.1 mg, maximum single dose 0.5 mg) - note that children require relatively higher doses than standard pediatric resuscitation 1

Dose Escalation Protocol

• Double the dose every 5 minutes until atropinization endpoints are reached - this doubling strategy is critical and differs from fixed-dose repetition 1, 2
• Continue escalation regardless of heart rate - tachycardia is NOT a contraindication to continued atropine administration, as it may result from nicotinic effects of the organophosphate itself 1
• Cumulative doses may reach 10-20 mg in the first 2-3 hours, with some patients requiring up to 50 mg in 24 hours 2

Endpoints of Atropinization

Stop escalation only when ALL of the following are achieved: 1, 2

• Clear chest on auscultation (no bronchorrhea)
• Heart rate >80 beats/min
• Systolic blood pressure >80 mm Hg
• Dry skin and mucous membranes
• Mydriasis (pupil dilation)

Maintenance Therapy

• Administer 10-20% of the total loading dose per hour (up to 2 mg/h in adults) via continuous infusion, which is preferred over intermittent boluses 2
• Maintain some degree of atropinization for at least 48 hours until depressed cholinesterase activity reverses 3

Pralidoxime (2-PAM) - Oxime Therapy

Pralidoxime has Class 2a recommendation with Level A evidence and should be administered early to reactivate acetylcholinesterase 1

Dosing

• Adults: 1-2 g IV loading dose administered slowly, preferably by infusion 1
• Maintenance: 400-600 mg/hour continuous infusion for adults or 10-20 mg/kg/hour for children 1
• Pralidoxime is most effective when given early, before "aging" of the phosphorylated enzyme occurs (generally within 36 hours of exposure) 3

Critical Principle

• Always administer atropine concurrently with pralidoxime - pralidoxime alone is insufficient to manage respiratory depression, as it addresses nicotinic effects (muscle weakness, fasciculations) while atropine addresses muscarinic effects (bronchorrhea, bradycardia) 1
• Do not withhold pralidoxime when the class of poison is unknown (organophosphate vs. carbamate), as organophosphate poisoning requires early oxime therapy and the two are clinically indistinguishable 1

Airway Management

• Perform early endotracheal intubation for life-threatening poisoning, particularly with bronchorrhea, bronchospasm, altered mental status, or respiratory failure 1
• Avoid succinylcholine and mivacurium - these neuromuscular blockers are metabolized by cholinesterase and are contraindicated in organophosphate poisoning 1
• Early recognition of respiratory failure and prompt intubation is life-saving, as respiratory failure is the major cause of mortality 4

Seizure and Agitation Management

• Administer benzodiazepines (diazepam or midazolam) for seizures and agitation 1
• Benzodiazepines also facilitate mechanical ventilation when needed 5

Gastric Decontamination

• Perform gastric lavage and administer activated charcoal via nasogastric tube for ingested organophosphates 4
• Healthcare workers performing gastric lavage must use PPE - documented cases show severe secondary poisoning from handling gastric contents 1
• Consider continuing absorption from the lower bowel, as fatal relapses have occurred after initial improvement, requiring additional pralidoxime doses every 3-8 hours 3

Monitoring and Supportive Care

• Monitor patients closely for at least 48-72 hours as delayed complications can occur 1, 3
• Provide continuous cardiac monitoring for dysrhythmias 1
• Support ventilation and oxygenation as needed 3
• Establish IV access and administer fluids for volume resuscitation 1

Watch for Complications

• Intermediate syndrome (delayed muscle weakness occurring 24-96 hours after acute exposure, even after initial improvement) - requires vigilant monitoring of respiratory rate and early intubation 4, 6
• Aspiration pneumonia from bronchorrhea 4
• Rhabdomyolysis with myoglobinuria causing renal damage - monitor creatine kinase and potassium, treat with hydration, forced diuresis, and urine alkalinization 1
• Atropine-induced fever and hallucinations - expected adverse effects with high-dose therapy that should never prompt premature discontinuation 1

Common Pitfalls to Avoid

• Never delay atropine administration - it is the immediate life-saving intervention 1, 2
• Never underdose atropine - organophosphate poisoning requires much higher doses than typical bradycardia treatment 1, 2
• Never stop atropine due to tachycardia - the therapeutic endpoint is control of muscarinic symptoms, not heart rate normalization 1
• Never use succinylcholine or mivacurium for intubation 1
• Never delay intubation in patients with increasing respiratory rate (e.g., from 22 to 38 breaths/min) - this is an important sign of respiratory distress requiring immediate intervention 4