Management of Organophosphate Poisoning
Immediately administer atropine 1–2 mg IV for adults (0.02 mg/kg for children, minimum 0.1 mg, maximum 0.5 mg per dose), doubling the dose every 5 minutes until full atropinization is achieved, while simultaneously giving pralidoxime 1–2 g IV loading dose followed by continuous infusion, along with aggressive decontamination and early intubation for severe cases. 1, 2
Immediate Decontamination and Personal Protection
Healthcare workers must wear appropriate personal protective equipment (PPE) before approaching the patient, as secondary exposure from contaminated clothing, skin, and gastric contents has caused severe poisoning in caregivers requiring atropine, pralidoxime, and even intubation. 1
Remove all contaminated clothing immediately and perform copious irrigation with soap and water for any dermal exposure—organophosphates can be absorbed through intact or damaged skin and cause life-threatening toxicity. 1, 3
Never allow staff to handle gastric contents, emesis, or perform gastric lavage without full PPE, as documented cases show healthcare workers developing severe organophosphate poisoning requiring 24 hours of mechanical ventilation after exposure to contaminated gastric aspirate. 1
Atropine: First-Line Life-Saving Therapy
Atropine is a Class 1, Level A recommendation and must be given immediately—this is the single most critical intervention. 1, 2
Initial Dosing Protocol
Adults: 1–2 mg IV bolus immediately upon recognition of severe poisoning (bronchospasm, bronchorrhea, seizures, or significant bradycardia). 1, 2
Children: 0.02 mg/kg IV/IO (minimum single dose 0.1 mg, maximum single dose 0.5 mg per dose)—note that standard pediatric resuscitation doses are insufficient and higher doses are required. 1
Dose Escalation Algorithm
Double the atropine dose every 5 minutes until full atropinization is achieved, defined by ALL of the following endpoints: 1, 2
- Clear chest on auscultation (resolution of bronchorrhea)
- Heart rate >80 beats/min
- Systolic blood pressure >80 mmHg
- Dry skin and mucous membranes
- Mydriasis (dilated pupils)
Typical cumulative requirements are 10–20 mg in the first 2–3 hours; severe cases may require up to 50 mg in the first 24 hours or even 1000 mg total over several days. 1, 4
Maintenance Therapy
Once atropinization is achieved, maintain with continuous IV infusion at 10–20% of the total loading dose per hour (not exceeding 2 mg/hour in adults). 1
Some degree of atropinization must be maintained for at least 48 hours until depressed cholinesterase activity reverses, with vigilant monitoring especially at night when supervision may lapse. 5, 4
Critical Management Principle: Do Not Stop Atropine for Tachycardia
Atropine-induced tachycardia is an expected pharmacologic effect and is NOT a contraindication to continued administration—the therapeutic endpoint is control of life-threatening muscarinic symptoms (bronchorrhea, bronchospasm, adequate blood pressure), not heart rate normalization. 1, 2
Tachycardia may originate from nicotinic receptor overstimulation by the organophosphate itself, not from atropine, making it even more critical to continue escalation. 1
The risk of undertreating organophosphate poisoning far exceeds the risk of atropine-induced tachycardia—inadequate atropinization leads to respiratory failure and death. 2
Never withhold or prematurely discontinue atropine due to fever, as repeated high-dose atropine produces central nervous system effects including fever and hallucinations, but these adverse effects are acceptable given the alternative of respiratory failure. 1
Pralidoxime (2-PAM): Essential Oxime Therapy
Pralidoxime has a Class 2a recommendation with Level A evidence and must be given early to reactivate acetylcholinesterase before "aging" occurs. 1, 5
Dosing Protocol
Adults: 1–2 g IV loading dose administered slowly over 15–30 minutes (preferably by infusion), followed by continuous infusion of 400–600 mg/hour. 1, 5
Children: 25–50 mg/kg IV loading dose over 15–30 minutes, followed by continuous infusion of 10–20 mg/kg/hour. 1
Timing Is Critical
Pralidoxime should be administered as soon as possible after atropine effects become apparent, ideally within minutes to hours after exposure—the organophosphate-acetylcholinesterase bond undergoes "aging" (becomes irreversible) within minutes for nerve agents like soman, or up to 24 hours for agricultural organophosphates, but efficacy drops by 50% after 6 hours. 1
Little is accomplished if pralidoxime is given more than 36 hours after termination of exposure, though continued absorption from the gastrointestinal tract constitutes new exposure and may require additional doses every 3–8 hours. 5
Mechanism and Rationale
Pralidoxime reverses nicotinic effects (muscle weakness, respiratory paralysis, potentially some tachycardia) that atropine cannot address—atropine only blocks muscarinic receptors and has minimal impact on nicotinic-mediated neuromuscular dysfunction. 1, 2
Always administer atropine concurrently with pralidoxime, as pralidoxime alone is insufficient to manage respiratory depression and muscarinic symptoms. 1
Do not withhold oximes when the class of poison (organophosphate vs. carbamate) is unknown, as clinical distinction is impossible and early oxime therapy is critical for organophosphates. 1, 6
Airway Management and Mechanical Ventilation
Early endotracheal intubation is recommended for life-threatening organophosphate poisoning, particularly when bronchorrhea, bronchospasm, altered mental status, or respiratory distress threatens airway protection—observational data suggest better outcomes with early intubation. 1, 2, 6
Avoid succinylcholine and mivacurium for intubation, as these neuromuscular blockers are metabolized by cholinesterase and are absolutely contraindicated in organophosphate poisoning due to prolonged paralysis. 1, 2, 6, 5
Early recognition of respiratory failure is life-saving—watch for increasing respiratory rate (e.g., from 22 to 38 breaths/min) as an important sign of impending respiratory distress requiring immediate intubation. 7
Respiratory failure is the most troublesome complication and major cause of mortality, occurring in up to 74% of patients due to aspiration, excessive secretions, pneumonia, or acute respiratory distress syndrome. 7
Seizure and Agitation Management
Administer benzodiazepines for seizures and agitation—diazepam 0.2 mg/kg IV or midazolam 0.05–0.1 mg/kg IV in fractionated doses. 1, 2, 6
Benzodiazepines are also useful to facilitate mechanical ventilation when needed. 1
Monitoring and Observation Period
All patients must be monitored closely for at least 48–72 hours, as delayed complications and fatal relapses can occur, especially with ingested organophosphates due to continued absorption from the gastrointestinal tract. 1, 2, 5
Continuous cardiac monitoring should be performed to detect dysrhythmias, but not to limit atropine dosing. 2
Serial respiratory assessments every 5–10 minutes during the escalation phase to auscultate for bronchorrhea resolution. 2
Intermediate Syndrome
Watch for delayed muscle weakness (intermediate syndrome) occurring 24–96 hours after acute exposure, even as the initial cholinergic crisis resolves—this syndrome was observed in 19% of patients in one series and requires mechanical ventilation. 1, 8, 7
Three patients with intermediate syndrome died due to delay in endotracheal intubation—increasing respiratory rate is a critical warning sign requiring immediate action. 7
Rhabdomyolysis and Renal Complications
Monitor creatine kinase and potassium levels for rhabdomyolysis, which results from excessive acetylcholine causing calcium flux into skeletal muscle leading to myocyte death and myonecrosis. 1
Reddish urine indicates myoglobin (from muscle breakdown), not hemoglobin—this is a crucial distinction that prevents misdiagnosis. 1
Treatment for rhabdomyolysis includes adequate hydration, forced diuresis, and urine alkalinization when myoglobinuria is present. 1
Gastric Decontamination
Gastric lavage and activated charcoal administration via nasogastric tube may be considered for ingested organophosphates, but only with full PPE due to the risk of secondary exposure to healthcare workers. 1, 7
"Titrate" the patient with pralidoxime as long as signs of poisoning recur, as continued gastrointestinal absorption constitutes new exposure and fatal relapses have been reported after initial improvement. 5
Drugs to Avoid
Do not use morphine, theophylline, aminophylline, reserpine, or phenothiazine-type tranquilizers in patients with organophosphate poisoning. 5
Atropine should not be given in the presence of significant hypoxia due to the risk of atropine-induced ventricular fibrillation—improve oxygenation first. 5
Carbamate Poisoning: Key Differences
The management algorithm for carbamate poisoning is identical to organophosphate poisoning (atropine, benzodiazepines, supportive care, early intubation), with the same dosing protocols. 6
Carbamates spontaneously dissociate from acetylcholinesterase (unlike organophosphates which cause permanent "aging"), but pralidoxime should still not be withheld when the poison class is unknown, as clinical distinction is impossible. 1, 6
Common Pitfalls to Avoid
Never delay atropine administration—it is the immediate life-saving intervention and must be given before any other therapy. 2, 6
Never underdose atropine—organophosphate poisoning requires much higher doses than typical bradycardia treatment, and aggressive escalation is mandatory. 2, 6
Never stop atropine escalation due to tachycardia or fever—these are expected effects and the risk of undertreating is fatal. 1, 2
Never delay intubation in patients with respiratory distress—early recognition and intervention is life-saving. 7
Never use succinylcholine or mivacurium for intubation—these are absolutely contraindicated. 1, 2, 6, 5
Never handle contaminated materials without PPE—secondary exposure to healthcare workers is well-documented and can be severe. 1