Acute poisoning

Poisoning is defined as the state resulting from the administration of excessive amounts of any pharmaceutical agent. For many healthcare professionals, it denotes exposure to a substance which is a danger to health or life. A poison may be a drug, household product, industrial chemical, or plant or animal derivative. The most common route of poisoning is by ingestion, but poisoning by inhalation, injection, skin/eye contamination, or bites may also occur¹ .

Epidemiology¹

• In 2020, 4,561 deaths related to drug poisoning were registered in England and Wales (equivalent to a rate of 79.5 deaths per million people). Of the 4,561 registered drug poisoning deaths, 66% (2,996) were related to drug misuse² .

• The incidence of acute poisoning in children under the age of 5 has reduced due to the introduction of initiatives such as blister packs and other safety measures.

• About 170,000 people are admitted to hospital in the UK each year with suspected poisoning. It is not known how many people are managed in the community, including NHS advice services.

• Accidental ingestion of pharmaceuticals by toddlers makes up 2% of Accident and Emergency attendances by this age group.

• Of the 54,757 hospital admissions in England for children under 5 due to poisoning between 2000 and 2012:

  • 77 % were due to poisoning with pharmaceuticals.

  • 38% were non-opiate analgesics.

  • Other causes of poisoning included organic solvents, corrosive substances, gases, soaps and detergents, pesticides and alcohol.

• Self-poisoning is most commonly seen in younger adults, aged between 15 and 35.

• Cases in the elderly can potentially be more serious, due to pre-existing comorbidities.

Most of the discussion below is confined to drug and chemical poisoning.

Types of poisoning³

• Alcohol intoxication is the most common type of acute poisoning. Suicide by medical drug overdose is the most common type of suicide by poisoning.

• Death from acute poisoning is most commonly the result of either smoke inhalation or illegal drug use.

• Severe poisoning is only rarely due to the ingestion of chemicals (particularly detergents and cleaning products), cosmetics, or plant matter.

Deliberate poisoning

• Overdose as self-harm or suicide attempt.

• Child abuse ± fabricated or induced illness by carers (formerly referred to as Münchhausen's syndrome by proxy).

• Third party (attempted homicide, terrorist, warfare).

Accidental poisoning

• Dosage error:
  

  • Iatrogenic

  • Patient error

• Recreational use.

• Environmental:

  • Plants

  • Food

  • Venomous stings/bites

• Industrial exposures.

Poisoning management^{1 4 5 6}

See specific management dependent on drug(s) involved (contact poisons centre or Toxbase® for current specific advice).

Resuscitation

Extent of resuscitation required depends on the state of the patient. See the Resuscitation Council (UK) guidelines on Adult Basic Life Support and Paediatric Basic Life Support^{7 8} .

Airway

• Open, suction, maintain and intubate as necessary.

Breathing

• Assess work and effectiveness of ventilation.

• Give oxygen ± assisted ventilation (avoid mouth-to-mouth).

• Respiratory depression - consider opiates, benzodiazepines.

• Tachypnoea: consider metabolic acidosis - eg, salicylates, methanol.

Circulation

• Attach a cardiac monitor, assess pulse, blood pressure and perfusion. Establish intravenous (IV) access.

• Tachycardia/irregular pulse - consider overdose of salbutamol, antimuscarinics, tricyclics, quinine, phenothiazine, chloral hydrate, cardiac glycosides, amfetamines and theophylline poisoning.

• If hypotensive, consider giving fluid bolus (colloid) or, if necessary, inotropes.

Disability

• Assess consciousness level - Glasgow Coma Scale or AVPU (= Alert, Voice, Pain, Unresponsive).

• Coma may suggest benzodiazepines, alcohol, opiates, tricyclics, or barbiturates.

• Check pupils and eye movements:
  

  • Large - consider anticholinergics, sympathomimetics, tricyclics.

  • Small - consider opiates or cholinergics.

  • If opiates are suspected, give 0.8-2 mg naloxone IV/intramuscularly (IM) every 2-3 minutes up to 10 mg until response (children: 10 micrograms/kg IV/IM repeated up to 0.2 mg/kg); repeated doses may be required thereafter, as it has a shorter half-life than most opiates.

  • Unreactive - causes include barbiturates, carbon monoxide, hydrogen sulfide, cyanide/cyanogens, head injury/hypoxia.

  • Unequal - slight variation can be normal - but consider head injury.

  • Strabismus - can be seen with carbamazepine overdose.

  • Papilloedema - associated with methanol, carbon monoxide and glutethimide.

  • Nystagmus - seen with CNS acting agents (eg, phenytoin).

• Check blood glucose - if hypoglycaemic, give 50 ml 50% dextrose IV (children: 5 ml/kg of 10% dextrose IV):
  

  • Hyperglycaemia - organophosphates, theophyllines, monoamine-oxidase inhibitors (MAOIs) or salicylate.

  • Hypoglycaemia - insulin, oral hypoglycaemics, alcohol or salicylate.

• Seizures - if prolonged/recurrent, initially give diazepam 5-10 mg IV (children: 0.25-0.4 mg/kg IV or PR) or midazolam (0.15 mg/kg) IM/IV. Many drugs can induce seizures, including tricyclics, theophylline, opiates, cocaine and amfetamines.

History

This may be unreliable but include the following:

• Ascertain what was taken, how much, when and by what route.

• Ask whether alcohol was consumed too.

• Establish whether there has been any vomiting since ingestion.

• Establish past medical history, current medications and allergies.

• Ascertain whether a suicide note was left.

• Ask whether the patient is pregnant.

• Histories from others, including family, friends, paramedics, police and observers.

Obtain the patient's past medical notes if possible.

General examination

• Directed cardiovascular, respiratory, abdominal and neurological examination.

• Vital signs, pupils, etc, mentioned in 'Resuscitation' section, above.

• Temperature - hypothermia (phenothiazines, barbiturates, or tricyclics) or hyperthermia (amfetamines, ecstasy, MAOIs, cocaine, antimuscarinics, theophylline, serotonin syndrome).

• Muscle rigidity (ecstasy, amfetamines).

• Skin - cyanosis (methaemoglobinaemia), very pink (carboxyhaemoglobinaemia, cyanide, hydrogen sulfide), blisters (barbiturates, tricyclic antidepressants (TCAs), benzodiazepines), needle tracks, hot/flushed (anticholinergics).

• Breath - ketones (diabetic/alcoholic ketoacidosis), 'bitter almonds' (cyanide), 'garlic-like' (organophosphates, arsenic), 'rotten eggs' (hydrogen sulfide), organic solvents.

• Mouth - perioral acneiform lesions (solvent abuse), dry mouth (anticholinergics), hypersalivation (parasympathomimetics).

Investigations

• 12-lead electrocardiogram.

• U&E, laboratory glucose, anion gap ± lactate and osmolal gap.

• LFTs and clotting.

• Arterial blood gases.

• Paracetamol level (also salicylates⁹ , theophylline, digoxin, lithium, antiepileptics - if it was likely that they had been taken).

• Comprehensive toxicology screens not normally indicated in the emergency treatment.

• Carboxyhaemoglobin levels if carbon monoxide poisoning is suspected.

• Urinalysis - query rhabdomyolysis; save sample for possible toxicological analysis.

• CXR if there is suspected pulmonary oedema/aspiration.

• CT scan of the brain may be needed to exclude other causes of alterations in conscious level.

Differential diagnosis

• Head trauma (especially, in the ethanol-intoxicated patient).

• Stroke/subarachnoid haemorrhage.

• Meningitis.

• Metabolic abnormalities (such as hypoglycaemia, hyponatraemia, or hypoxaemia).

• Liver disease.

• Post-ictal state

Poisoning treatment

Obtain more information

• UK National Poisons Information Centres 0344 892 0111 (automatically routed to the nearest centre - available to health professionals but not the general public)¹⁰ .

• Toxbase®: NHS intranet and internet-based information from the National Poisons Information Centre (registration free to NHS GPs and hospitals)¹¹ .

• MIMS Colour Index or TICTAC (a computer-aided tablet and capsule identification system available to authorised users, including Regional Drug Information Centres and Poisons Information Centres): to aid pill identification.

• British National Formulary (BNF)/Data Sheet Compendium.

Decontamination if appropriate

• Avoid contaminating yourself and wear protective clothing.

• Ensure the area is well ventilated.

• The patient should remove soiled clothing and wash themself if possible.

• Put soiled clothing in a sealed container.

• Wash all contaminated skin/hair with liberal amounts of warm water ± soap.

Decrease absorption

• Single-dose activated charcoal is the preferred method of decontamination in many cases. Patients should have had a significant overdose, be co-operative, without impairment of consciousness and not thought to be likely to fit imminently. Ideally it is used in a 10:1 ratio with the ingested drug - the usual dose is 50 g for an adult (children: 1 g/kg). It may be repeated in one hour if necessary (oral, nasogastric tube). Its large surface area adsorbs many drugs but has its limitations. It may not be effective if given after the first hour or in cases of poisoning with iron, lithium, boric acid, cyanide, ethanol, ethylene glycol, methanol, malathion, DDT, carbamate, hydrocarbon or strong acids or alkalis.
  
  Any oral antidotes given after charcoal may be rendered ineffective.
  
  

• Gastric emptying is contra-indicated if the airway is unprotected or an overdose of corrosives or hydrocarbons has been taken. Complications include pulmonary aspiration and oesophageal perforation. Only 30% of gastric contents are returned and it is proven to be effective if within one hour of ingestion (so this is only generally done if patients present early having taken a potentially fatal dose of drug). Controversially, this is sometimes extended if delayed gastric emptying (eg, presence of coma or overdose of tricyclics or salicylates) is thought likely:
  

  • Emesis is no longer recommended.

  • Gastric lavage is used in cases where medications have been ingested that activated charcoal would absorb poorly (eg, iron, lithium) and for sustained-release formulations or enteric-coated tablets. It is carried out by placing the patient in the left lateral head-down (20°) position, inserting a large (36-40F) bore tube (children: 16-28F) into the stomach. Remove contents with sequential administration and aspiration of small (200-300 ml) quantities of warm water or saline (children: 10-20 ml/kg preferably saline). Alternatively, the stomach contents can just be aspirated.

• Whole bowel irrigation is also useful in cases where poisoning is due to substances which would not be absorbed by activated charcoal. It uses a large volume of an osmotically balanced, non-absorbable polyethylene glycol electrolyte solution (eg, Klean-Prep®, GoLYTELY®). Used with iron and other heavy metals, lithium, sustained-release or enteric-coated products, large ingestions and ingested drug packets. Administer at 1-2 L per hour PO or NG (children: 30 ml/kg/hour); antiemetics may be required; continue until rectal effluent is clear (approximately 3-6 hours). This is rarely used.

Increase elimination

• Multiple doses of activated charcoal - interrupts enterohepatic or enteroenteric recirculation. Use 50 g four-hourly (children 1 g/kg) or 12.5 g hourly (children 0.25 g/kg) to reduce vomiting but beware severe constipation and fluid depletion. Used with carbamazepine, dapsone, phenobarbital, quinine, salicylate, colchicine, dextropropoxyphene, digoxin, verapamil and theophylline overdoses.

• Forced diuresis - no longer recommended.

• Haemoperfusion and acid/alkaline diuresis - rarely used now.

• Haemodialysis - severe salicylate, ethylene glycol, methanol, lithium, phenobarbital and chlorate poisonings.

Supportive

• Maintain ABCDs.

• Observation and treatment of late complications - eg, liver failure, rhabdomyolysis.

Specific antidote

See individual articles for relevant antidotes and antagonists.

Referral

• Medical/paediatric - for continued support/antidote administration, observation, cardiac monitoring.

• Psychiatric - for all deliberate self-poisonings, those with suicidal ideation and if the country's Mental Health Act has been employed to detain/treat.

Psychiatric assessment

See Suicide Risk Assessment and Threats of Suicide.

Prevention

• Adult education.

• Double-check dosage before administration.

• Vigilance by health professionals to recognise the early signs of abuse and potential suicide.

• Put all medicines and household chemicals in a locked child-proof cupboard >1.5 metres off the ground.

• Safely dispose of medicines and chemicals which are not needed or are out of date.

• Keep all medicines and chemicals in their original containers with clear labels.