PE14.2 | Organophosphorus Poisoning — Summary & Reflection

KEY TAKEAWAYS

Organophosphorus poisoning — key take-home points:

• OP compounds irreversibly inhibit acetylcholinesterase (AChE), causing acetylcholine accumulation at muscarinic and nicotinic synapses throughout the body.

• The cholinergic toxidrome = muscarinic features (SLUDGE: salivation, lacrimation, urination, defaecation, GI cramps, emesis — plus miosis, bradycardia, bronchospasm) + nicotinic features (fasciculations, weakness, paralysis — respiratory failure is the most common cause of death) + CNS features (seizures, coma).

• Two antidotes, two mechanisms:
• Atropine: muscarinic antagonist — blocks SLUDGE/bronchospasm/bradycardia. No maximum dose — titrate to secretion dryness, not a fixed endpoint. Does NOT treat nicotinic effects.
• Pralidoxime (PAM): AChE reactivator — must be given within 24–48 hours before irreversible ageing of the OP-AChE bond. Reverses both muscarinic and nicotinic effects.

• Airway management is critical — respiratory muscle paralysis and bronchial hypersecretion both threaten the airway; intubate early if respiratory failure is developing.

• Seizures: benzodiazepines (diazepam 0.2–0.3 mg/kg IV or midazolam 0.1 mg/kg).

• Decontaminate first (remove clothing, wash skin) — dermal absorption continues if the compound remains on the child.

REFLECT

The hook case presented a child whose atropine was underdosed by a paramedic who gave '0.5 mg — a full dose' — a dose that might be adequate for bradycardia from a vagal reflex but is a fraction of what severe OP poisoning requires. Reflect on the cognitive error at work: the paramedic applied a standard cardiac atropine dose to a toxicological emergency with a completely different dose-response relationship. In OP poisoning, the target is not a number — it is a clinical state (secretions dry). How would you brief a junior colleague, a nurse, or a paramedic on the atropine dosing rule in OP poisoning in a way they would remember under pressure? Consider also: how would you counsel the family of this child about pesticide storage safety — sensitively, without blame, and with specific actionable steps they can take today?