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, eg. rat poison
• Intended poisoning, ie. suicidal or homicidal
• Occupational hazard, eg. 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

Differential diagnosis

• Other causes of poisoning
• Other causes of convulsions
• Acute infection

Management
HC4

Remove contaminated clothing

Wash contaminated skin with lots of cold water

Establish and maintain the airway

- artificial respiration with air or oxygen may be required during the first 24 hours after poisoning

Perform gastric lavage if the poison was ingested

atropine 2mg IM or IV (according to the severity of the poisoning) child: 20 micrograms/kg per dose

- repeat dose every 20-30 minutes until signs of atropinization occur (pupil dilatation, hot dry skin, dry mouth, fast pulse)

In moderate to severe poisoning only and if not responding to atropine:

Add pralidoxime mesylate 30mg/kg IM

- follow by 1-2 more doses at 4-6 hour intervals depending on the severity of the poisoning and response to treatment

In very severe poisoning:

- the initial dose may be doubled

- usual maximum dose: 12g/24 hours

- the dose can also be given by slow IV (over a 5 minute period) by diluting 1g in 10-15mL of water for injection or by IV infusion (up to 500mg/hour may be required)

Give IV fluids prn for dehydration, hypovolaemia and shock, see p354

Note

♦ pralidoxime: only effective if given within 24 hours of poisoning

Prevention

• Label agricultural and domestic pesticides properly
• Store such products away from children
• Wear protective clothing when using the products