What is the treatment for extrasystoles, Ventricular Tachycardia (VT) and Atrial Fibrillation (AF) after organophosphorus poisoning?

Treatment for Cardiac Arrhythmias After Organophosphorus Poisoning

Atropine is the first-line treatment for cardiac arrhythmias including extrasystoles, ventricular tachycardia (VT), and atrial fibrillation (AF) following organophosphorus poisoning. 1 Immediate administration of atropine is essential to counteract the cardiotoxic effects of acetylcholinesterase inhibition.

Primary Management Algorithm

Step 1: Immediate Atropine Administration

• Initial dose: 2-3 mg IV 2
• Repeat every 20-30 minutes until full atropinization is achieved 1
• Target endpoints:
  • Clear chest on auscultation
  • Heart rate >80/min
  • Systolic blood pressure >80 mm Hg
• Maintenance: Continuous atropine infusion after initial stabilization 1

Step 2: Airway Management

• Early endotracheal intubation for patients with severe poisoning 1
• Avoid succinylcholine and mivacurium as neuromuscular blockers (contraindicated in organophosphate poisoning) 1

Step 3: Benzodiazepine Administration

• Diazepam (first line) or midazolam for seizures and agitation 1
• Also helps in managing cardiac arrhythmias by reducing sympathetic drive

Step 4: Oxime Therapy

• Pralidoxime administration is reasonable for organophosphate poisoning 1
• Typical dose: 1-2 g IV, followed by infusion
• Helps restore cholinesterase activity, potentially improving cardiac function

Specific Management for Cardiac Arrhythmias

For Extrasystoles

• Usually resolve with adequate atropinization
• Monitor ECG continuously as these may be precursors to more serious arrhythmias

For Ventricular Tachycardia (VT)

• Continue aggressive atropinization
• Consider magnesium sulfate (2-4 g IV over 10-15 minutes) 3
• Avoid lidocaine as it has been reported ineffective in organophosphate-induced VT 4
• For refractory cases, consider isoproterenol 3
• In hemodynamically unstable VT, electrical cardioversion may be necessary

For Atrial Fibrillation (AF)

• Usually resolves with adequate atropinization and detoxification 5
• Rate control with beta-blockers should be avoided initially as they may worsen bradycardia
• For persistent AF after adequate atropinization, follow standard AF management protocols 1
• Consider cardioversion only after adequate atropinization and stabilization

Additional Important Measures

• Decontamination: Remove contaminated clothing and perform thorough skin washing with soap and water 1
• Use appropriate personal protective equipment to prevent secondary contamination 1
• Monitor ECG continuously as QT prolongation is common (62.6%) and may precede serious arrhythmias 4
• Correct electrolyte abnormalities, particularly potassium and magnesium
• Maintain adequate oxygenation and acid-base balance

Pitfalls and Caveats

• Delayed cardiac complications: Cardiac manifestations may appear up to 24 hours after initial presentation 3
• Rebound cholinergic effects: Premature discontinuation of atropine can lead to recurrence of symptoms
• QT prolongation: Monitor closely as it may predispose to torsades de pointes
• Sodium bicarbonate: While useful for sodium channel blocker toxicity, there is insufficient evidence for its routine use in organophosphate-induced arrhythmias
• Avoid certain antiarrhythmics: Traditional antiarrhythmics like lidocaine may be ineffective for organophosphate-induced VT 4

Cardiac monitoring should continue for at least 72 hours after apparent clinical recovery, as delayed cardiac complications can occur and may be fatal if not promptly addressed.