Toxicology and Environmental Emergencies
Domain focus
The Toxicology and Environmental Emergencies domain tests toxidrome recognition, decontamination, antidote selection, and environmental illness. The exam rewards pathophysiologic reasoning over memorized lists.
Core rules
- Toxidromes: opioid (miosis, respiratory depression) → naloxone; anticholinergic (dry, flushed, mydriasis, delirium) → supportive care; cholinergic (SLUDGE/bronchorrhea) → atropine and pralidoxime; sympathomimetic → benzodiazepines.
- Acetaminophen overdose: N-acetylcysteine, ideally within 8 h; use the Rumack-Matthew nomogram for single ingestion.
- Salicylate toxicity: sodium bicarbonate to alkalinize urine and plasma, correct hypokalemia, avoid intubation unless necessary.
- Toxic alcohol: fomepizole; hemodialysis for severe acidosis.
- Carbon monoxide: 100% oxygen; hyperbaric oxygen for severe neurologic or cardiac involvement.
- Heat stroke: rapid evaporative cooling; do not use antipyretics.
Worked example
A farmer presents with miosis, bradycardia, bronchorrhea, and muscle fasciculations after spraying. This is cholinergic toxicity from organophosphate exposure. Decontaminate and protect staff, give atropine in escalating doses until secretions dry, then pralidoxime. The reasoning is toxidrome-based: bronchorrhea and fasciculations point to acetylcholinesterase inhibition, so atropine treats muscarinic effects and pralidoxime reactivates enzyme.
Traps
Do not give flumazenil in mixed overdose or seizure history. Charcoal is contraindicated in unprotected airway and caustic ingestion. Gastric lavage is not routine. In CO poisoning, pulse oximetry is falsely normal.