Treatment of Organophosphate (OP) Poisoning
The cornerstone treatment for organophosphate poisoning includes immediate decontamination, atropine administration, pralidoxime therapy, and benzodiazepines for seizures, along with supportive care for respiratory and cardiovascular function. 1
Initial Management
Decontamination
- Remove patient from exposure source immediately
- Remove all contaminated clothing
- Wash skin and hair thoroughly with soap and water before patient enters healthcare facility 1
- Healthcare providers must wear appropriate PPE (respiratory protection, gloves, gowns, eye protection) to prevent secondary exposure 1
Supportive Care
- Establish and maintain airway
- Provide respiratory support (often mechanical ventilation is required)
- Maintain cardiovascular support
- Correct metabolic abnormalities
- Control seizures 2
Pharmacological Treatment
Atropine
- First-line antimuscarinic agent to block parasympathetic overstimulation
- Initial dosing: 2-4 mg IV in adults 1, 2
- Repeat every 5-10 minutes until atropinization is achieved (secretions inhibited) 2
- Maintenance: 10-20% of loading dose per hour (up to 2 mg/h) 1
- Continue atropinization for at least 48 hours and until cholinesterase activity improves 2
- Note: Atropine should NOT be given in presence of significant hypoxia due to risk of ventricular fibrillation 2
Pralidoxime (Oxime Therapy)
- Reactivates acetylcholinesterase enzyme to reverse nicotinic effects
- Initial dosing: 1-2 grams IV over 15-30 minutes in adults 1, 2
- Second dose may be given after one hour if muscle weakness persists 2
- Maintenance: 400-600 mg/hour (adults) for at least 24-48 hours 1
- Continuous infusion shows better outcomes than intermittent bolus dosing 1
- Most effective if initiated within 36 hours of poisoning 2
- "Titrate" with pralidoxime as long as signs of poisoning recur 2
Benzodiazepines
- Essential for prevention and treatment of seizures 1
- Also helps reduce anxiety and agitation
Monitoring and Follow-up
Diagnostic Testing
- Measure cholinesterase activity in blood (RBC acetylcholinesterase and plasma cholinesterase) 1
- Reduction below 50% of normal indicates poisoning 1
- Monitor cholinesterase activity, creatine kinase, and serum potassium levels 1
Observation Period
- Observe patient for at least 48-72 hours after exposure 2
- Monitor for recurrence of symptoms, particularly with ingested OPs (due to continued absorption from lower bowel) 2
Clinical Manifestations to Monitor
Muscarinic Effects (SLUDGE syndrome)
- Salivation, Lacrimation, Urination, Defecation, GI upset, Emesis
- Bronchorrhea, bronchospasm, bradycardia
- Miosis (pupillary constriction) 1
Nicotinic Effects
- Muscle fasciculations, weakness, paralysis
- Tachycardia, hypertension 1
CNS Effects
- Altered mental status, seizures, confusion 1
Special Considerations
Contraindications
- Avoid succinylcholine, mivacurium, morphine, theophylline, aminophylline, reserpine, and phenothiazine-type tranquilizers 1, 2
- These medications may worsen OP poisoning or interact adversely
Pediatric Considerations
- Infants and young children may present with drowsiness rather than muscle twitching 1
- Some symptoms like drooling may be normal in young children 1
Complications to Monitor
- Respiratory failure (most common cause of mortality - 74.4% of cases) 1
- Intermediate syndrome
- Aspiration pneumonia
- Neurologic impairment
- Acute respiratory distress syndrome (ARDS) 1
Pitfalls and Caveats
- Do not delay treatment while waiting for laboratory confirmation - treat based on clinical suspicion 1
- Ensure proper decontamination before patient enters healthcare facility to prevent secondary contamination 1
- Continuous monitoring is essential as fatal relapses have been reported after initial improvement 2
- Pralidoxime is most effective when given early - little benefit if given >36 hours after exposure 2
- Mechanical ventilation is associated with higher mortality (50% vs 21.6% in non-ventilated patients) 1