ACUTE ORGANOPHOSPHATE POISONING

Organophosphates are ingredients of some pesticides and insecticides intended for agricultural and household use.

Poisoning occurs by ingestion, inhalation or absorption through the skin.

Causes

  • May be accidental, e.g., contamination of food
  • Intended poisoning, i.e., suicidal or homicidal
  • Occupational hazard, e.g., agricultural workers

Clinical features

  • Patient may smell of the chemicals
  • Constricted pupils
  • Cold sweat, anxiety, restlessness
  • Abdominal pain, diarrhoea and vomiting
  • Twitching, convulsions
  • Bradycardia
  • Excessive salivation, difficulty in breathing, abundant respiratory secretions
  • Headache, hypotension, urine incontinence
  • Coma

Differential diagnosis

  • Other causes of poisoning
  • Other causes of convulsions

Management

  • Remove contaminated clothing (use gloves)
  • Wash contaminated skin with lots of water
  • Establish and maintain the airway
  • Atropine 2-4 mg IM or IV (according to the severity of the poisoning)
    Child: 0.05 mg/kg per dose

    • Double dose every 3-5 minutes until signs of atropinisation occur (stopping of bronchial secretions and broncoconstrictions)
    • Continuous infusion of atropine 0.05 mg/kg/hour may be necessary
    • Reduce dose of atropine slowly over 24 hours but monitor for patient’s status
  • Assisted respiration with air or oxygen may be required during the first 24 hours after poisoning
  • Give IV fluids, e.g., normal saline prn for dehydration, hypovolaemia, and shock
  • Prevent and treat convulsions with diazepam 10mg IV
    Child: 0.2 mg/kg IV or 0.5 mg/kg rectal
  • Salbutamol 5 mg (2.5 mg for children <5 years) nebulisation if bronchospasm:
  • Perform gastric lavage if the poison was ingested (up to 6 hours after ingestion) but consider risk of aspiration
  • Give standard dose of activated charcoal if patient presents within 2 (up to 4) hours
  • Monitor patient for a few days (worsening can occur a few days after ingestion)
In moderate to severe poisoning (only if not responding to adequate doses of atropine)
  • Add pralidoxime mesylate 30 mg/kg IV over 30 minutes
    Child: 25-50 mg/kg IV

    • Continue with infusion 8 mg/kg/hour
      Child: 10-20 mg/kg/hour

Note

  • Pralidoxime: Only effective if given within 24 hours of poisoning

Prevention

  • Label agricultural and domestic pesticides properly – do not use unlabelled bottles for pesticides
  • Store such products away from children
  • Wear protective clothing when using the products