Pharmacology, Toxicology and Addiction MedicineTier 2Approach to a presentation

Poisonings - pesticides

Red flags

Cholinergic toxidrome features (excessive salivation, lacrimation, urination, defecation, bronchorrhoea/bronchospasm, bradycardia, miosis) following organophosphate/carbamate exposure indicate potentially life-threatening poisoning requiring immediate treatment
Respiratory compromise from bronchorrhoea and bronchospasm is the major cause of death and requires urgent airway management and atropine

Differential by mechanism

Organophosphate/carbamate poisoning (cholinesterase inhibition - occupational, agricultural, or deliberate self-poisoning exposure, the classic and most dangerous pesticide toxicity)

Other pesticide classes (pyrethroids - generally lower toxicity, paraquat - a distinct, highly lethal herbicide with different management)

Non-pesticide cause of cholinergic symptoms (rare, but the clinical pattern is distinctive enough that alternative causes are uncommon confounders)

Focused history

Exposure circumstances (occupational spraying, agricultural work, accidental household exposure, deliberate self-poisoning - relevant to both diagnosis and psychosocial assessment), specific product/agent if known or available (bring the container if possible), time since exposure and route (dermal, inhalational, ingestion)
Symptom evolution, given some organophosphates can cause delayed or biphasic toxicity

Focused examination

Full cholinergic toxidrome assessment - DUMBBELS mnemonic features (defecation, urination, miosis, bradycardia/bronchorrhoea/bronchospasm, emesis, lacrimation, salivation), plus muscarinic and nicotinic features (fasciculations, weakness) depending on severity
Respiratory status is the priority given bronchorrhoea/bronchospasm as the major life-threatening feature

Investigation strategy

Plasma/red cell cholinesterase levels can support diagnosis and severity assessment, though clinical assessment should guide immediate treatment rather than waiting for results given the urgency
ECG monitoring given bradycardia and other cardiac effects

Management

Decontamination (remove contaminated clothing, wash skin - with staff PPE to avoid secondary contamination, a genuine risk with organophosphates) alongside standard resuscitation
Atropine, titrated to drying of secretions and reversal of bronchorrhoea/bronchospasm (not to a fixed dose - doses required can be very large and repeated)
Pralidoxime (an oxime, reactivating acetylcholinesterase) given alongside atropine in significant organophosphate poisoning, most effective if given before the enzyme-organophosphate bond "ages" and becomes irreversible

Traps

Delaying decontamination and staff PPE - organophosphates readily cause secondary contamination of treating staff without protective precautions

Under-dosing atropine - titrate to secretion drying/bronchospasm reversal, not a fixed maximum dose, since severe poisoning can require very large cumulative doses

Missing delayed/biphasic toxicity - some agents cause a delayed intermediate syndrome with recurrent weakness after apparent initial recovery, requiring extended observation

Talk track

"This chemical is affecting the nerve signals in your body, causing the excess saliva, sweating and breathing difficulty you're experiencing - we're going to give you a medicine called atropine to counteract this, and we may need to give quite large or repeated doses depending on how you respond, alongside close monitoring of your breathing."

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