General Principles of Acute Poisoning

Terminating topical exposures to poisons
Gastric lavage
Early post-ingestion activated charcoal
Multiple-dose activated charcoal (MDAC)

Have a high index of suspicion in patients that present with symptoms and signs which are difficult to explain.

Identify the substance, ideally through obtaining the original toxic substance or container. If not available, identify through an accurate history.

Plasma concentration measurements are essential for the following poisons: carboxyhaemoglobin in carbon monoxide poisoning, paracetamol, salicylates, theophylline, tricyclic antidepressants, lithium, digoxin, and metals.

Useful investigations in most poisonings include: serum electrolytes, blood glucose, arterial blood gas, osmolality, liver and kidney function tests, INR, urinalysis, and an ECG.

Terminating topical exposures to poisons

• Contaminated clothing should be removed and safely disposed of.
• Wash skin and hair with soap and water while wearing gloves.
• Eye exposure: irrigate with copious amounts of water or saline for 10-15 minutes.

Gastric lavage

• Indication: ingestion of large amounts of tablets and capsules with a high inherent toxicity with 2 hours.
• Method:
  • Insert a large-bore orogastric tube (32-40 F in adults and 24-28 F in children) into the oesophagus.
  • Place patient head down, left lateral decubitus.
  • Aspirate fluid from stomach prior to fluid lavage.
  • Install water or saline into stomach: adult 200-300 ml; children 10ml/kg.
  • Aspirate fluid back and dispose of fluid. Repeat lavage until aspirate clear of debris or pill fragments.
• Risks: pulmonary aspiration, epistaxis, laryngospasm, hypoxia, sinus bradycardia, and mechanical injury.
• Contraindications: patients with decreased LOC, unprotected airway, ingestions of corrosive agents, volatile hydrocarbons, and who are at risk of gastrointestinal haemorrhage.

Early post-ingestion activated charcoal

• Minimising systemic absorption from the gastrointestinal tract.
• Indication: consider use if within 1 hour of ingestion of the poisonous substance.
• Method:
  • Route: oral or instil via NG tube.
  • Adult dose: 50-100g (1-1.5g/kg) as a slurry in 400-800 ml water (8mL of water to 1g of charcoal).
  • Paediatric dose: Under 6 years, 10g in 50-100 ml water; older children, 20-50g in 200-300ml water.
  • Shake vigorously to ensure adequate dispersion of charcoal.
• Avoid (no value): strong acids, alkalis, corrosives, heavy metals (e.g. iron salts), cyanides, lithium, organophosphates, petroleum products (including paraffin), methanol, and ethylene glycol.
• Risks: no systemic effects, but may induce vomiting, constipation, diarrhoea, and gastrointestinal.
• Contraindicated: decreased LOC or unprotected airway.

Multiple-dose activated charcoal (MDAC)

• Enhance elimination of drugs already absorbed into the body by interrupting enterohepatic circulation of drugs excreted into the bile.
• Indication: ingestion of life-threatening amount of carbamazepine, dapsone, phenobarbitone, quinine, theophylline, salicylate, digoxin, sotalol, or sustained-release formulations.
• Method: After first dose of activated charcoal as above, follow-up dose of 25g every 2 hours, or 50g every 4 hours until clinical condition and laboratory parameters (including drug concentrations) improve.
• Contraindicated: diminished bowel sounds, proven ileus, or small-bowel obstruction. Do not use with cathartics.