Poisons Flashcards
What needs to be asked when taking a history for poisoning?
Intentional or accidental?
What has been consumed?
How long ago?
How much?
What are the general principles of management of poisoning?
ABCDE
Reduce absorption –> decontamination
Alter metabolism –> antidotes
Increase elimination –> kidneys
Which investigations can be done for poisoning?
Test blood level of substance (only a few)
Associated pathology –> renal failure, rhabdomyolysis, hyperkalaemia
ABGs –> acid/base derangement, ventilatory failure
ECG
Which substances can be tested for in the blood to confirm toxicity/guide therapy?
Paracetamol
Salicylates
Ethylene glycol
Lithium
Why in an ECG useful and which important abnormality must be checked for?
May demonstrate signs of cardio toxicity and will guide management
–> QTc (increase risk of malignant arrhythmia)
Which methods of gut decontamination can be used for certain toxins?
Activated charcoal
Bowel irrigation
(forced emesis not recommended)
Where should you look for management of specific toxins?
Toxbase
What is the antidote for paracetamol?
N-acetylcysteine
Methionine
What is the antidote for tricyclic antidepressants?
Sodium bicarbonate
What is the antidote for beta blockers?
Glucagon
What is the antidote for ethylene glycol + methanol?
Ethanol
Fomepizole
What is ethylene glycol?
Antifreeze
What are the antidotes for cyanide?
Hydroxycobalamin
Sodium nitrate
Sodium thiosulphate
What is the antidote for iron salts?
Desferrioxamine
What is the antidote for opioids?
Naloxone
What are the antidotes for organophosphates?
Atropine
Pralidoxime mesylate
What are the methods of increasing elimination to treat poisoning?
Urinary alkalinisation
Haemodialysis
Haemofiltration
Give an example of using urinary alkalinisation to treat poisoning
Treat aspirin overdose with sodium bicarbonate –> increases elimination via kidneys
Give some examples of poisonings that can be treated with haemodialysis
Alcohols e.g. methanol
Lithium
Aspirin
Which poisonings can be treated with haemofiltration?
Theophyllines
Carbamazepine
How much paracetamol ingestion warrants referral to hospital for assessment?
> 75mg/kg
How is paracetamol metabolised in therapeutic doses?
Mostly converted to non-toxic metabolites
But 5% converted to highly reactive intermediary metabolite –> NAPQI
NAPQI is detoxified by conjugation with glutathione in the liver
What happens to paracetamol metabolism in paracetamol overdose?
Excess paracetamol –> more NAPQI
Hepatocellular supplies of glutathione become depleted + NAPQI remains in toxic form
–> widespread hepatocyte damage + death –> acute liver necrosis
What are the initial features of paracetamol poisoning?
Nausea and vomiting –> extremely common
Very rarely –> coma + severe metabolic acidosis (extremely high plasma paracetamol)
What are the later features of paracetamol poisoning?
In severe cases:
- abdominal pain (12-36 hours)
- hepatic necrosis after 2-3 days: RUQ pain + tenderness, N&V, jaundice, AKI, hepatic encephalopathy
What are the indications for starting treatment for paracetamol poisoning?
Blood paracetamol levels checked at 4 hours + plotted on graph
–> commence treatment if level is above line
How quickly should treatment for paracetamol poisoning be started and what should be done if the patient presents late?
Should commence within 8 hours of ingestion
If presentation delayed (>8 hours) start treatment and await blood results
Which blood tests should be done following treatment for paracetamol overdose?
LFTs
U&Es
INR
Which blood test is the most accurate indictor of synthetic liver function following paracetamol overdose?
INR
How should the blood tests following paracetamol overdose treatment be interpreted?
If bloods normal –> treatment can be stopped
If bloods deranged –> N-acetyl cysteine treatment must be continued
What is the antidote for benzodiazepines?
Flumazenil
