What is the immediate management of a suspected organophosphate poisoning?

Immediate Management of Organophosphate Poisoning

Administer atropine 1-2 mg IV immediately 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 ensuring personal protective equipment, decontamination, airway management, and early pralidoxime administration. 1, 2

Personal Protection and Decontamination (First Priority)

• Healthcare workers must wear personal protective equipment before patient contact to prevent secondary contamination—documented cases exist of providers requiring atropine, pralidoxime, and intubation after exposure to contaminated gastric contents or emesis. 2
• Immediately remove all contaminated clothing and irrigate skin/hair copiously with soap and water (or sodium bicarbonate/alcohol) to halt ongoing dermal absorption. 2, 3

Atropine Administration (Life-Saving Intervention)

Initial Dosing

• Adults: 1-2 mg IV bolus immediately upon recognition of severe poisoning (bronchospasm, bronchorrhea, seizures, significant bradycardia). 1, 4
• Children: 0.02 mg/kg IV (minimum 0.1 mg, maximum 0.5 mg per single dose)—note this is substantially higher than standard pediatric resuscitation doses. 1, 4

Dose Escalation Protocol

• Double the atropine dose every 5 minutes (not fixed-dose repetition) until all atropinization endpoints are met. 1, 4
• Do NOT stop escalation due to tachycardia—tachycardia may result from nicotinic receptor overstimulation by the organophosphate itself, not atropine, and is an expected pharmacologic effect. 1
• Typical cumulative requirements: 10-20 mg in the first 2-3 hours; some patients need up to 50 mg in 24 hours. 4

Atropinization Endpoints (All Must Be Achieved)

• Clear chest on auscultation (resolution of bronchorrhea) 1
• Heart rate >80 beats/min 1
• Systolic blood pressure >80 mm Hg 1
• Dry skin and mucous membranes 1
• Mydriasis (pupil dilation) 1

Maintenance Therapy

• After achieving atropinization, continue as continuous infusion at 10-20% of total loading dose per hour (up to 2 mg/h in adults), not intermittent boluses. 4
• Maintain atropinization for at least 48-72 hours due to risk of delayed complications and relapses, especially with ingested organophosphates causing continued GI absorption. 1, 3

Pralidoxime (Oxime Therapy)

Timing and Rationale

• Administer pralidoxime early—ideally within minutes to hours after exposure—before the organophosphate-acetylcholinesterase bond undergoes "aging" and becomes irreversible (occurs within minutes for nerve agents like soman, up to 24 hours for agricultural organophosphates, but efficacy drops 50% after 6 hours). 2
• Pralidoxime reverses nicotinic effects (muscle weakness, fasciculations, respiratory failure) that atropine cannot address. 1, 2

Dosing

• Adults: 1-2 g IV loading dose administered slowly over 15-30 minutes, followed by continuous infusion of 400-600 mg/hour. 1, 3
• Children: 25-50 mg/kg IV loading dose over 15-30 minutes, followed by 10-20 mg/kg/hour continuous infusion. 2
• American Heart Association gives pralidoxime Class 2a recommendation with Level A evidence—strong recommendation with high-quality evidence. 2

Critical Principle

• Never withhold pralidoxime when the class of poison (organophosphate vs. carbamate) is unknown. 2

Airway Management

• Early endotracheal intubation is recommended for life-threatening organophosphate poisoning—observational data suggest better outcomes with early intubation. 1, 2
• Avoid succinylcholine and mivacurium for intubation—these neuromuscular blockers are metabolized by cholinesterase and are contraindicated in organophosphate poisoning. 1, 2, 3

Seizure and Agitation Management

• Administer benzodiazepines (diazepam first-line or midazolam) for seizures and agitation. 1, 2
• Pediatric dosing: Diazepam 0.2 mg/kg IV or midazolam 0.05-0.1 mg/kg IV in fractionated doses. 2

Monitoring and Observation

• Continuous cardiac monitoring to detect dysrhythmias (not to limit atropine dosing). 1
• Serial respiratory assessments every 5-10 minutes during escalation phase to auscultate for bronchorrhea resolution. 1
• Monitor creatine kinase and potassium levels for rhabdomyolysis detection—organophosphates cause myonecrosis from calcium flux into skeletal muscle. 2
• Maintain close observation for at least 48-72 hours as delayed complications and fatal relapses can occur from continued GI absorption. 1, 3

Gastric Decontamination (If Ingested)

• Consider gastric lavage and activated charcoal for recent ingestions, but only with full PPE for healthcare workers—documented cases of severe secondary poisoning from handling gastric contents. 2
• Induce diarrhea to prevent continued lower bowel absorption—fatal relapses have been reported after initial improvement. 3

Critical Pitfalls to Avoid

• Never delay atropine administration—it is the immediate life-saving intervention with Class 1, Level A evidence. 4
• Never stop atropine escalation due to tachycardia—the risk of undertreating organophosphate poisoning far exceeds the risk of atropine-induced tachycardia. 1
• Never withhold pralidoxime while waiting for toxicology confirmation—early administration is critical before enzyme aging occurs. 2
• Never use atropine in the presence of significant hypoxia—correct hypoxemia first to avoid atropine-induced ventricular fibrillation. 3