Treatment of Organophosphate Poisoning
The treatment of organophosphate poisoning requires immediate administration of atropine to counteract cholinergic effects, followed by pralidoxime to reactivate acetylcholinesterase, along with proper decontamination and supportive care. 1
Initial Management
- Ensure proper personal protective equipment (PPE) when caring for patients with organophosphate exposure to prevent secondary contamination of healthcare providers 2, 1
- For external exposure, immediate dermal decontamination by removing contaminated clothing and copious irrigation with soap and water is essential 1
- Administer atropine immediately at 1-2 mg IV for adults (0.02 mg/kg for children), doubling the dose every 5 minutes until bronchorrhea, bronchospasm, and bradycardia resolve (full atropinization) 1
- Maintain atropinization for at least 48 hours, and until any depressed blood cholinesterase activity is reversed 3
Airway Management
- Early endotracheal intubation is recommended for life-threatening organophosphate poisoning 1
- Avoid neuromuscular blockers metabolized by cholinesterase (succinylcholine and mivacurium) as they may cause prolonged paralysis in patients with organophosphate poisoning 1, 3
Antidote Administration
Atropine
- Initial dose: 1-2 mg IV for adults (0.02-0.1 mg/kg for children) 1
- Double the dose every 5 minutes until secretions are inhibited (full atropinization) or signs of atropine toxicity appear (delirium, hyperthermia, muscle twitching) 3
- Atropine should not be given in the presence of significant hypoxemia due to the risk of atropine-induced ventricular fibrillation 3
Pralidoxime (2-PAM)
- Administer pralidoxime as soon as possible after hypoxemia is improved and atropine has been given 1, 3
- Initial dose: 1000-2000 mg IV, preferably as an infusion in 100 mL of normal saline over 15-30 minutes 3
- If infusion is not practical or pulmonary edema is present, administer slowly over at least 5 minutes as a 50 mg/mL solution 3
- A second dose of 1000-2000 mg may be given after about one hour if muscle weakness has not been relieved 3
- Additional doses may be given every 10-12 hours if muscle weakness persists 3
- Treatment is most effective if initiated immediately after poisoning, with diminishing effectiveness if given more than 36 hours after exposure 3
Seizure Management
- Administer benzodiazepines (such as diazepam or midazolam) to treat seizures and agitation 1, 4
- Benzodiazepines stimulate GABA receptors, which can help counteract the glutamatergic hyperactivity caused by organophosphate poisoning 4
Supportive Care
- Maintain airway, breathing, and circulation 1
- Provide supplemental oxygen as needed 1
- Monitor vital signs continuously 1
- Observe the patient for at least 48 to 72 hours, as relapses can occur, especially with ingested organophosphates due to continued absorption from the lower bowel 3
Special Considerations
- In cases of ingestion, consider the likelihood of continuing absorption from the lower bowel, which constitutes new exposure and can cause fatal relapses after initial improvement 3
- Avoid medications that may worsen organophosphate poisoning: morphine, theophylline, aminophylline, reserpine, and phenothiazine-type tranquilizers 3
- For patients with ongoing absorption or recurrent symptoms, "titrate" with pralidoxime as long as signs of poisoning recur 3
Common Pitfalls and Caveats
- Failure to use proper PPE when treating organophosphate poisoning can lead to secondary exposure of healthcare providers 2
- Delaying atropine administration can result in worse outcomes; atropine should be given immediately once hypoxemia is improved 1
- Pralidoxime is most effective when administered early, before "aging" of the phosphorylated enzyme occurs 1
- Intravenous administration of pralidoxime should be carried out slowly as rapid administration can temporarily worsen cholinergic manifestations 3
- Continuous infusion of pralidoxime may maintain therapeutic levels longer than intermittent therapy 3