Toxicological, Environmental and Envenomation Emergencies
The toxidrome approach
Identify the syndrome, then the agent. Anticholinergic: dry flushed skin, mydriasis, delirium, urinary retention, tachycardia. Cholinergic: salivation, lacrimation, urination, diarrhoea, bronchorrhoea, bradycardia, miosis - organophosphates need decontamination, atropine titrated to secretions, and an oxime. Opioid: pinpoint pupils with respiratory depression - titrate naloxone to breathing, not to full consciousness. Sympathomimetic: agitation, sweating, hypertension, dilated pupils.
Paracetamol: use the nomogram from 4 hours post-ingestion; give N-acetylcysteine empirically if the timing is unknown, presentation is late, or there is hepatic injury. Salicylate: tinnitus, tachypnoea, mixed acidosis - alkalinise with sodium bicarbonate. Tricyclic overdose: widened QRS and arrhythmia - sodium bicarbonate boluses. Beta-blocker: glucagon and high-dose insulin. Carbon monoxide: 100% oxygen, with hyperbaric therapy considered for neurological features, syncope or pregnancy. Cyanide: hydroxocobalamin.
Heat stroke requires immediate cooling by ice-water immersion - cool first, transport second - and may affect young athletes. Hypothermia: handle gently, rewarm, and remember nobody is dead until warm and dead.
Envenomation: pressure-immobilisation and antivenom for elapid snakebite; supportive care for scorpion stings; hot water immersion for marine stings.
Rule of thumb: in any overdose give oxygen, check glucose, obtain a 12-lead ECG and a paracetamol level, and look for the one toxin that has an antidote.