What are the recommended atropine dosing guidelines, including initial bolus, repeat dosing, infusion rates, and clinical endpoints, for adults and children with suspected organophosphate poisoning?

Atropine Guidelines for Organophosphate Poisoning

Initial Dosing

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), then double the dose every 5 minutes until complete atropinization is achieved—defined as clear lungs, dry skin, heart rate >80/min, systolic BP >80 mmHg, and mydriasis. 1, 2, 3

• The initial adult dose of 1-2 mg is substantially higher than the 0.5-1.0 mg used for bradycardia from other causes, reflecting the severity of organophosphate toxicity 3
• The FDA label confirms 2-3 mg as the initial dose for organophosphate poisoning, repeated every 20-30 minutes 4
• Children require relatively higher doses per kilogram compared to standard pediatric resuscitation protocols 2

Dose Escalation Protocol

The critical principle is aggressive, rapid escalation by doubling the dose every 5 minutes—not fixed-dose repetition—until all atropinization endpoints are met. 1, 2, 3

• Continue escalation regardless of heart rate; tachycardia is NOT a contraindication to continued atropine administration 2, 3
• The therapeutic endpoint is control of life-threatening muscarinic symptoms (bronchorrhea, bronchospasm, bradycardia), not heart rate normalization 1, 2
• Patients commonly require cumulative doses of 10-20 mg in the first 2-3 hours, with some requiring up to 50 mg in 24 hours 1, 3, 5

Clinical Endpoints of Atropinization

Stop escalation only when ALL of the following are achieved 2, 3:

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

Maintenance Infusion

After achieving initial atropinization, administer 10-20% of the total loading dose per hour (up to 2 mg/h in adults) as a continuous infusion. 1, 2, 3

• Continuous infusion is preferred over intermittent boluses for maintenance therapy 3
• Pediatric maintenance: 10-20 mg/kg/hour 2
• Maintenance may be required for days to weeks, as organophosphate-enzyme bonds undergo "aging" and restoration of normal acetylcholinesterase activity can take up to 6 weeks 3

Essential Concurrent Therapies

Always administer pralidoxime concurrently with atropine, as atropine alone is insufficient to manage respiratory depression and nicotinic effects. 2, 3

• Pralidoxime dosing: 1-2 g IV loading dose for adults (25-50 mg/kg for children), followed by continuous infusion at 400-600 mg/hour for adults (10-20 mg/kg/hour for children) 1, 2
• Administer pralidoxime early before "aging" occurs (within minutes to hours), after which it becomes ineffective 2, 3
• Give benzodiazepines (diazepam 0.2 mg/kg or midazolam 0.05-0.1 mg/kg) for seizures and agitation 1, 2

Airway Management

Perform early endotracheal intubation for life-threatening organophosphate poisoning, with observational data suggesting better outcomes with early intubation. 2

• Avoid succinylcholine and mivacurium—these neuromuscular blockers are metabolized by cholinesterase and are contraindicated in organophosphate poisoning 1, 2

Critical Pitfalls to Avoid

Never delay atropine administration—it is the immediate life-saving intervention with Class 1, Level A evidence from the American Heart Association. 2, 3

• Underdosing is the most common error: Organophosphate poisoning requires aggressive, high-dose atropine therapy that may seem excessive by conventional standards 3, 5
• Do not stop atropine due to tachycardia—the tachycardia may be from nicotinic receptor overstimulation by the organophosphate itself, not atropine toxicity 2
• Do not stop atropine due to fever—fever is an expected adverse effect with high-dose therapy and does not indicate treatment failure 2
• Ensure adequate atropine and pralidoxime supplies are available in hospitals, as total requirements can be substantial (up to 11.6 g atropine over 12 days reported) 5

Decontamination and Safety

Use proper personal protective equipment (PPE) when caring for organophosphate-exposed patients to prevent secondary contamination of healthcare workers. 2

• Remove contaminated clothing and perform copious irrigation with soap and water for dermal exposure 2
• Healthcare workers performing gastric lavage are at significant risk of secondary exposure from gastric contents, with documented cases requiring atropine, pralidoxime, and intubation 2

Monitoring Duration

Monitor patients for at least 48-72 hours, as delayed complications including muscle weakness can occur as late as 4 days after acute exposure. 2, 6

• Monitor for rhabdomyolysis (creatine kinase, potassium), myonecrosis, and renal damage from calcium overload in skeletal muscle 2, 6
• Serial glucose and potassium monitoring every 4-6 hours if high-dose therapy was required 6