Describe the general management of a case of acute poisoning including decontamination and antidotes.

The Sequence

• 1. Resuscitation and stabilisation — always first. Airway, breathing, circulation
• oxygen
• intravenous access
• the "coma cocktail" where indicated: glucose (after or with thiamine), thiamine, naloxone and oxygen. Treat convulsions, arrhythmia, hypotension and hyperthermia → 2.
• Rapid assessment — the toxidrome from the pupils, secretions, skin, temperature, bowel sounds and mental state
• the history from every available source → 3.
• Decontamination — skin, eyes and gastrointestinal tract → 4.
• Enhanced elimination — where a specific technique is effective for that poison → 5.
• Antidote — where one exists, which is for a minority of poisons → 6.
• Supportive and intensive care — which is what actually saves most patients → 7.
• Psychiatric assessment and follow-up before discharge in every deliberate self-poisoning

Decontamination

Enhanced Elimination and Antidotes

• Urinary alkalinisation with sodium bicarbonate — for salicylates and phenobarbitone; it traps the ionised drug in the tubule
• Multiple-dose activated charcoal — interrupts enterohepatic circulation; for carbamazepine, dapsone, phenobarbitone, quinine and theophylline
• Haemodialysis — for poisons that are small, water-soluble, poorly protein-bound and with a small volume of distribution: methanol, ethylene glycol, salicylates, lithium, and theophylline
• Haemoperfusion — largely superseded; forced diuresis is no longer recommended because of the risk of fluid overload

• Classification of antidotes — mechanical or physical (activated charcoal, demulcents such as milk and egg white, bulky food); chemical (potassium permanganate, tannic acid, calcium for oxalate); and physiological or pharmacological, which act by opposing the effect at the receptor and are the group listed above
• The "universal antidote" — a historical mixture of activated charcoal, magnesium oxide and tannic acid — is discredited and must not be used; it is less effective than charcoal alone

Applied Aspects

• Resuscitate before you identify; the airway and the circulation do not wait for a diagnosis, and most deaths are from airway loss and aspiration rather than from the poison itself
• Give thiamine before or with glucose in any malnourished or alcoholic patient; glucose alone precipitates Wernicke encephalopathy
• Never lavage a corrosive or a hydrocarbon; the first perforates and the second is aspirated, and both errors are made regularly
• Preserve the first gastric aspirate before instilling anything, sealed and labelled; it is the specimen with the highest concentration and the greatest evidential value
• Do not use forced diuresis or the universal antidote; both are obsolete, and the first causes harm
• Arrange psychiatric assessment before discharge after every deliberate self-poisoning; a previous attempt is the strongest predictor of a completed suicide and this is where the opportunity lies
• Charcoal does not bind PHAILS — pesticides, hydrocarbons, acids and alkalis, iron, lithium and solvents
• Emesis with ipecacuanha is abandoned; it delays charcoal, risks aspiration and has no demonstrated benefit
• Haemodialysis suits small, water-soluble, poorly bound poisons — methanol, ethylene glycol, salicylate, lithium and theophylline
• Urinary alkalinisation traps salicylate in the tubule, and multiple-dose charcoal interrupts enterohepatic circulation
• Flumazenil may precipitate convulsions and is used with caution, particularly where a tricyclic has also been taken
• Ethanol and fomepizole both compete for alcohol dehydrogenase, and either will block the conversion of methanol to formic acid
• Pralidoxime works for organophosphates but not carbamates, whereas atropine is given for both
• Do not neutralise a chemical on the skin; the reaction is exothermic and adds a thermal burn to a chemical one
• The universal antidote is discredited and less effective than charcoal alone; it should not be used
• Irrigate the eye for at least twenty minutes, and far longer for alkali, which continues to penetrate
• Digoxin Fab also treats oleander, which is a common cardiac plant poison in southern India
• Sodium bicarbonate narrows the QRS in tricyclic overdose, and is the specific measure for the cardiac toxicity
• Pyridoxine is the antidote to isoniazid, given gram for gram with the ingested dose to control the convulsions