Updated: 12/22/2017

Organophosphate Poisoning

Review Topic
  • A 53-year-old farmer presents to the emergency room with shortness of breath and difficulty breathing. He reports dusting his crops with pesticide at the time of onset. On physical exam, he has excessive salivation, sweating, and lacrimation. His pupils are constricted and he has audible wheezes with each breath. He is immediately given atropine and decontaminated.
  • Clinical definition
    • organophosphate poisoning that results in increased acetylcholine activity
  • Epidemiology
    • demographics
      • farmers or other workers who are exposed to insecticides
      • industrial workers
    • risk factors
      • occupational exposure
  • Etiology
    • insecticides
      • e.g., malathion, parathion, and fenthion
    • nerve gas
      • most rapid and most severe
    • ophthalmic agents
      • e.g., echothiophate and isofluophate
    • herbicide
      • e.g., merphos and tribufos
    • industrial chemicals
      • e.g., tricresyl phosphate
  • Pathogenesis
    • organophosphates irreversibly inhibit acetylcholinesterase and block the metabolism of acetylcholine, resulting in increased acetylcholine activity
      • this causes overstimulation of the muscarinic and nicotinic receptors
  • Prognosis
    • good with treatment, though patients may require intubation before stabilization
  • Symptoms
    • salivation, sweating, rhinorrhea, and lacrimation
    • involuntary urination or defecation
    • nausea, diarrhea, and vomiting
    • anxiety
  • Physical exam
    • wheezing
      • from bronchospasm
    • miosis and blurred vision
    • bradycardia and hypotension
    • fasciculations
    • seizures
    • Diarrhea, Urination, Miosis, Bronchospasm, Bradycardia, Excitation of systems, Lacrimation, Sweating, Salivation
  • Labs
    • typically not indicated but can be confirmed by measurement of
      • red blood cell cholinesterase levels
      • plasma cholinesterase levels
  • Making the diagnosis
    • most cases are clinically diagnosed
  • Viral gastroenteritis
    • distinguishing factor
      • primarily gastrointestinal upset without other muscarinic and nicotinic effects
  • Conservative
    • remove clothes and wash the patient
      • indications
        • for all patients
        • for the protection of caregivers and other patients, as organophosphates can be absorbed through the skin
  • Medical
    • atropine
      • indication
        • antidote for all patients as initial therapy
          • competitive inhibitor
    • pralidoxime
      • indication
        • antidote for all patients shortly after atropine is given
          • reactivates acetylcholinesterase
    • benzodiazepines
      • indication
        • for patients with seizures or fasciculations
  • Respiratory failure
  • Seizures

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