Atropine Dosing for Organophosphorus-Induced Cardiac Arrhythmias
For organophosphorus poisoning-induced cardiac arrhythmias (VT, AF, extrasystoles), administer atropine immediately at an initial dose of 2-3 mg IV, repeated every 20-30 minutes until full atropinization is achieved, with doses doubled every 5 minutes if needed. 1, 2
Dosing Protocol for Organophosphorus-Induced Cardiac Toxicity
Initial Dosing
- Initial dose: 2-3 mg IV bolus 2
- If no response within 5 minutes, double the previous dose
- Continue doubling doses every 5 minutes until atropinization is achieved
Signs of Adequate Atropinization
- Clear chest on auscultation (absence of bronchorrhea/secretions)
- Heart rate >80 beats/minute
- Systolic blood pressure >80 mmHg 1
- Resolution of bronchospasm
Maintenance Therapy
- After initial atropinization, maintain with continuous IV infusion
- Titrate infusion based on recurrence of cholinergic symptoms
- Total doses required may be extremely high (reported cases using up to 3000 mg) 3, 4
Special Considerations
Severity-Based Approach
- For severe poisoning with cardiac manifestations, aggressive atropinization is essential
- Patients with ventricular tachycardia, atrial fibrillation, or frequent extrasystoles require higher initial doses
- The total cumulative dose may need to be much higher than standard cardiac protocols
Monitoring During Treatment
- Continuous ECG monitoring is mandatory
- Monitor respiratory status closely
- Watch for signs of atropine toxicity (confusion, hallucinations, hyperthermia)
- Assess for resolution of cholinergic symptoms
Important Caveats
- Doses <0.5 mg may cause paradoxical bradycardia and should be avoided 1
- Standard cardiac dosing protocols (0.5-1 mg) are insufficient for organophosphate poisoning
- Inadequate atropinization is a common pitfall in management
- Delayed atropinization significantly increases mortality
- Some patients may require extremely high doses (several grams) over the course of treatment 4
Adjunctive Therapy
- Pralidoxime (2-PAM) should be administered concurrently at 1-2 g IV initially, followed by continuous infusion at 7.5 mg/kg/hr 1, 3
- Early endotracheal intubation is recommended for severe poisoning 1
- Benzodiazepines should be used to control seizures and agitation 1
The key to successful management is recognizing that organophosphorus poisoning requires much higher atropine doses than typical cardiac protocols, with aggressive initial dosing and careful titration based on clinical response rather than adhering to standard maximum dose limits.