Organophosphate Poisoning

Initial Assessment and Stabilization

Airway, Breathing, and Circulation (ABCs)

• Airway: Ensure the airway is open and protected. If the patient is unconscious or showing signs of respiratory distress, early intubation may be necessary.
• Breathing: Administer 100% oxygen. Respiratory support, including mechanical ventilation, may be required due to bronchospasm, excessive secretions, or respiratory muscle weakness.
• Circulation: Monitor vital signs closely. Establish intravenous (IV) access to administer fluids and medications. Hypotension should be treated with IV fluids; if refractory, consider vasopressors.

Decontamination

• Remove from Exposure: Immediately remove the patient from the source of exposure (e.g., remove contaminated clothing, wash the skin thoroughly with soap and water).
• Gastric Decontamination: If ingestion occurred within 1 hour, consider gastric lavage followed by activated charcoal to limit absorption. This is typically reserved for severe cases.

Specific Antidotal Therapy

Atropine

• Mechanism: Atropine is a competitive antagonist of acetylcholine at muscarinic receptors, reversing the effects of excessive cholinergic activity (e.g., bronchorrhea, bradycardia, miosis).
• Dosing:
  • Start with 1-3 mg IV for adults (0.05 mg/kg for children). If there is no response, double the dose every 3-5 minutes until muscarinic symptoms (e.g., bronchial secretions, bradycardia) are controlled.
  • In severe cases, very high doses of atropine may be needed.
• Endpoint: Adequate atropinization is indicated by dry mucous membranes, improved heart rate, and resolution of bronchorrhea. Tachycardia alone is not an indication to stop atropine.

Pralidoxime (2-PAM)

• Mechanism: Pralidoxime reactivates acetylcholinesterase by cleaving the bond between the enzyme and the organophosphate before “aging” (a process where the OP-enzyme bond becomes irreversible). It is particularly effective for reversing nicotinic effects, such as muscle weakness and paralysis.
• Dosing:
  • Adults: 1-2 grams IV over 30 minutes, repeated every 12 hours if symptoms persist.
  • Children: 20-50 mg/kg IV (up to 1 gram) over 30 minutes, repeated as needed.
• Timing: Administer as soon as possible, ideally within hours of exposure to maximize effectiveness.
• Continuous Infusion: In severe cases, a continuous infusion may be required after an initial bolus.

Benzodiazepines

• Indication: For seizures or severe agitation.
• Dosing: Diazepam or lorazepam IV as needed to control seizures.

Supportive Care

Respiratory Support

• Mechanical ventilation may be required if the patient develops respiratory failure due to central nervous system depression or neuromuscular weakness.

Fluid and Electrolyte Management

• Administer IV fluids to maintain adequate blood pressure and organ perfusion. Monitor and correct any electrolyte imbalances.

Monitoring

• Continuous monitoring of vital signs, oxygen saturation, and neurological status is essential.
• Serial measurements of acetylcholinesterase activity can be useful to gauge the severity of poisoning and response to treatment, although clinical improvement is the primary endpoint.

Additional Therapies

• Glycopyrrolate: Sometimes used as an adjunct to atropine for controlling excessive secretions without crossing the blood-brain barrier (it does not cause CNS effects).
• Intravenous Lipid Emulsion (ILE): This therapy is controversial but has been used in severe cases of lipid-soluble OP poisoning to sequester the toxin in a lipid phase, reducing its bioavailability.

Monitoring and Follow-Up

ICU Care

• Patients with severe OP poisoning typically require intensive care unit (ICU) admission for close monitoring and supportive care.

Monitoring for Complications

• Intermediate Syndrome: A condition that can occur 24-96 hours after exposure, characterized by muscle weakness, particularly in respiratory muscles. Continuous monitoring is essential for early detection.
• Delayed Neuropathy: Some OPs can cause delayed peripheral neuropathy, manifesting days to weeks after exposure.

Prognosis and Long-Term Care

Prognosis

• Early and aggressive management significantly improves outcomes, but severe poisoning may still result in prolonged hospitalization, complications, or death.

Psychological Support

• Psychological support may be necessary, especially in cases of intentional poisoning.

Occupational Health and Safety

• For occupational exposure, review and improve safety protocols to prevent future incidents.