Poisoning Flashcards
Define a poison.
A substance taken internally or applied externally that is injurious to health or dangerous to life
Give examples of chemical agents that can cause toxicity.
Drugs Insecticides/herbicides Plant/animal toxins Chemical weapons Radioactive elements Bites/stings Carbon monoxide
What are the essential questions to ask when gathering information in suspected poisoning/drug overdose?
What drug(s) were taken? Try to locate containers How much was taken? When was the drug taken? Was the drug taken with alcohol or any other drugs or chemical? What is the age of the patient? What symptoms are the patient experiencing? Is the patient conscious? Is the patient breathing?
What should be considered when conducting an examination of someone with suspected poisoning/drug overdose?
Level of consciousness
Respiratory effort and cyanosis (i.e. aspirin)
Blood pressure and pulse rate (i.e. beta-blockers)
Pupil size and reaction to light (i.e. opiates)
Head injury or addiction (needle tracks)
Cough and gag reflex (if unconscious)
Temperature (if unconscious)
What are the common symptoms of overdose?
Nausea and vomiting Agitation Dizziness Weakness Confusion/loss of consciousness Hallucinations Seizures Coma
What are the direct effects of Spice?
Acute psychosis Panic Hallucinations Paranoia Arrhythmia Convulsions Multi-organ failure
Describe the use of activated charcoal in overdose/poisoning.
Most effective if administered within one or two hours
For overdoses of drugs that enter enterohepatic recirculation, multiple doses may be used providing bowel sounds are present i.e. carbamazepine, phenobarbitone, theophylline, quinine
Main risk is aspiration if a patient has an unprotected airway
Usual dose is 50g in adults, 1g/kg bodyweight for children under 12
Good absorption of most drugs and chemicals except for metals, alcohols, acids or alkalis
When is whole bowel irrigation indicated? What is used?
Ingestion of high doses of medicines such as iron or lithium
Involves oral administration of polyethylene glycol until rectal effluent is clear
1.5-2L/hr usually continued for 2-6 hours
What can be done in overdose of weakly acidic drugs?
Urinary alkalinisation with sodium bicarbonate
Aim for pH of 7.5-8.5 and blood gases monitored regularly
Hypokalaemia may make it difficult to achieve this
When is haemodialysis/perfusion used?
Aspirin, lithium, ethylene glycol or methanol
May be necessary in renal failure or severe metabolic acidosis
Charcoal haemoperfusion may be used in patients with severe theophylline or carbamazepine poisoning
What is the antidote for paracetamol? Describe its use.
N-acetylcysteine (Parvolex), acts as glutathione donor
If administered within first 8 hours of non-staggered overdose, almost 100% effective in preventing related hepatotoxicity
May still be used up to 24 hours after ingestion
What is the antidote for opioids? Describe its use.
Naloxone widely used as antidote
Competitive antagonist for opiate drugs
Ideally given IV but available IM, intranasal or endotracheal
Very short duration of action
Indicated where patients have significant drowsiness associated with respiratory compromise or hypoxia
Initially given to improve alertness and consciousness level (Glasgow Coma Scale)
Used as a diagnostic tool in unconscious patients to determine whether patient has overdosed on opioids
What is the antidote for BZDs? Describe its use.
Flumazenil is a competitive antagonist of benzodiazepines acting at GABA receptors
Symptoms are usually mild and resolve within 12-24 hours
More significant signs such as respiratory or cardiovascular depression may occur in patients who ingest other CNS depressants
Contraindicated in mixed overdoses with cardiotoxic or proconvulsant drugs
What are the three groups of cyanide antidotes?
Cobalt compounds
Sulphur donors
Methaemaglobinaemia formers
Describe the effects of cyanide.
Inhibits cellular respiration via reversible binding to cytochrome oxidase
Clinical features due to tissue hypoxia
What should be given ASAP in cyanide poisoning?
Give oxygen as soon as possible and correct metabolic acidosis
List 4 examples of cyanide antidotes.
Dicobalt edetate
Hydroxocobalamin
Sodium nitrite
Sodium thiosulphate
What is the antidote for toxic alcohols? Describe its use.
Ethanol (preferred substrate) or fomepizole given
Metabolites are the toxic agents, both metabolised by alcohol dehydrogenase
Antidotal treatment blocks this metabolism
Give 2 toxic alcohols often taken in overdose. Where are they commonly found?
Ethylene glycol and methanol, commonly found in antifreeze or engine fuel
What is the antidote for CCBs?
First line treatment of hypotension is fluid resus followed by calcium salts
High dose insulin-dextrose infusion may be indicated where unresponsive
What is the antidote for beta-blockers?
May not respond to fluid challenge or atropine
Glucagon can be given here IV over 5-10 minutes
Occasionally an anti-emetic may be given due to risk of hyperglycaemia with large dose of glucagon
What is the antidote for sulphonylureas?
Intravenous dextrose given
Can act as further stimulus for pancreatic insulin release
Diazoxide can be used to avoid this but may be problematic in sodium retention and hypotension
Octreotide is a long-acting somatostatin analogue inhibiting pancreatic insulin
