What is the treatment for extrasystoles and ventricular tachycardia (VT) in organophosphorus poisoning?

Treatment of Extrasystoles and VT in Organophosphorus Poisoning

Immediate administration of atropine is the cornerstone treatment for cardiac arrhythmias including extrasystoles and ventricular tachycardia in organophosphorus poisoning. 1

Primary Management Algorithm

1. Initial Cardiac Stabilization:

   • Administer atropine immediately for cardiac manifestations (Class I, Level A recommendation) 1
   • Initial dose: Double the dose every 5 minutes until full atropinization is achieved
   • Target: Clear chest on auscultation, heart rate >80/min, systolic BP >80 mmHg
   • Maintenance: Continue atropine infusion to maintain atropinization

2. For Ventricular Tachycardia and Extrasystoles:

   • Ensure adequate atropinization first (most important step)
   • For persistent VT despite atropine:
     • Consider sodium bicarbonate (1-2 mEq/kg IV) if QRS prolongation is present 1
     • Benzodiazepines (diazepam preferred) for associated agitation/seizures 1

3. Advanced Cardiac Support:

   • Early endotracheal intubation for respiratory compromise (Class I, Level B-NR) 1
   • For refractory VT/cardiac instability, VA-ECMO may be considered (Class 2b) 1
   • Avoid neuromuscular blockers metabolized by cholinesterase (succinylcholine, mivacurium) 1

Specific Cardiac Manifestations and Management

Extrasystoles

Extrasystoles in organophosphorus poisoning are common (reported in up to 33% of cases) 2 and typically respond to:

• Adequate atropinization (primary treatment)
• Correction of hypoxia and acidosis
• Avoidance of QT-prolonging medications

Ventricular Tachycardia

VT in organophosphorus poisoning is life-threatening (mortality reported in 5 of 6 cases in one study) 2 and requires:

• Aggressive atropine administration
• For refractory VT:
  • Magnesium sulfate may be effective when lidocaine and electrical cardioversion fail 3
  • Isoproterenol has shown efficacy in case reports 3
  • Sodium bicarbonate if QRS prolongation is present 1

Important Considerations

• ECG monitoring: Continuous monitoring is essential as QTc prolongation (62.6% of cases), ST elevation (25.2%), and T-wave inversion (19.6%) commonly precede serious arrhythmias 2

• Pralidoxime: Reasonable to administer for organophosphate poisoning (Class 2a, Level A) 1, but primarily affects nicotinic symptoms rather than cardiac manifestations

• Pitfalls to avoid:

  • Inadequate atropine dosing (much higher doses required than for typical bradycardia)
  • Failure to recognize early ECG changes (prolonged QTc is often the first sign)
  • Using conventional antiarrhythmics alone without addressing the underlying cholinergic crisis
  • Delayed intubation in patients with respiratory compromise

• Special consideration: Ventricular arrhythmias in organophosphate poisoning often don't respond to conventional treatments like lidocaine or cardioversion, making atropine administration the most critical intervention 3

Adjunctive Measures

• Dermal decontamination for external exposure (Class 1, Level C-EO) 1
• Use of appropriate personal protective equipment (Class 1, Level C-LD) 1
• Benzodiazepines for seizures and agitation (Class 1, Level C-LD) 1
• Supportive care including correction of electrolyte abnormalities and acid-base disturbances

The management of cardiac arrhythmias in organophosphate poisoning differs significantly from standard ACLS protocols, with atropine being the primary treatment rather than conventional antiarrhythmics.