managing a poisoned patient

Question 1

what do you need to ask in a history of a poisoned patient?

Answer 1

you need to establish exactly what they took (tricky with brand/ street names) - what tablets did you take? are you sure? is that all you took?

did you take any other drugs or alcohol? Think about interactions, even with regular medications etc.

if they are prescription meds you need to know whether they are prescribed for that particular patient or for someone else as this may make them more tolerable

you need to establish time of ingestion - this is particularly important for certain drugs such as paracetamol.

always consider why the patient took the overdose

• what did you think was going to happen?
• did you tell anyone? - indicates whether they wanted help
• how did you come to be in hospital? - self admission and regret vs someone found them etc
• did you leave a note? - this suggests intent to end life
• was the overdose planned?

Question 2

what can you look out for in an examination of a poisoned patient?

Answer 2

do a full exam but you can specifically look out for certain signs

eye signs

• small pupils (mitosis) - opiates
• large pupils (mydriasis) - sympathomimetics and anticholinergics
• conjunctival haemorrhage - protracted vomiting / trauma
• jaundice - late presentation in paracetamol overdose caused hepatotoxicity

other signs

• IV track marks
• self harm
• injuries suggesting violence / abuse
• extensive bruising from long lie (has been unconcious/ semiconcious for a long time)

Question 3

What is long lie? why are we worried about it?

how is it investigated?

Answer 3

If someone has been unconscious, semiconscious or unable to get up from a fall for a long time then this increases the risk of rhabdomyolysis.
This happens as there is hypoxic muscle damage which causes the release of muscle cell contents into the blood stream (creatinine kinase, myoglobin and potassium)
Myoglobin precipitation in the kidney can cause renal failure and will present with coca cola coloured urine.

To investigate this you do a blood test and measure the levels of creatinine kinase.

Question 4

What typical investigations would you do for a poisoned patient?

Answer 4

• obs - oxygen saturations are really important. so is temperature as cocaine, amphetamines, ecstasy and serotonergic drugs cause hyperthermia
• ABG - detect hypercapnia
• 12 lead ECG or cardiac monitor
• U&Es and creatinine - check kidney function
• glucose
• liver function tests - check liver function, especially in paracetamol overdose
• INR and clotting factors - especially in paracetamol overdose
• creatinine kinase - rhabdomyolysis
• specific drug assays - save a bottle of blood and urine from early in the presentation in case you need specific assays done as this will give a more accurate concentration, especially if you are unsure what the drug is on presentation.
• imaging may be required if you suspect aspiration pneumonia or ingested objects (body smugglers)

Question 5

what are the 4 different areas of management for a poisoned patient?

Answer 5

• symptomatic and supportive measures
• reducing absorption
• enhancing elimination
• specific antidotes

Question 6

How can the absorption of drugs be reduced?

Answer 6

Gastric lavage - this is very rarely done and only really has a benefit if done within an hour of the drugs being taken

single dose of activated charcoal - this can be used for patients that present within one hour of overdose as the charcoal binds to the drug to prevent absorption. It does not work for alcohol, glycols, acid/alkalis, lithium or iron

whole bowel irrigation - This is usually done for body packers. 2 litres per hour of preparations (orally or NG if not tolerated) until the bowel is effluent cleanse. This ensures the drug passes through the bowel quickly before it can be absorbed.

Question 7

How can the elimination of drugs be enhanced?

Answer 7

multiple dose of activated charcoal - this is totally different to single dose activated charcoal which prevents absorption. It enhance the elimination of drug absorbed by gastrointestinal dialysis. It is effective for carbamazepine, quinine, theophylline and dapsone.

urine alkalinisation - administration of IV sodium bicarbonate to achieve a pH of urine of 7.5-8.5. This is done in salicylate poisoning

extracorporeal elimination - haemodialysis or hemofiltration can be done when the poisoning is complicated by renal failure or to enhance elimination in specific poisonings such as ethanol, ethylene glycol, methanol, salicylates and lithium.

chelating agents - used in heavy metal poisoning eg. sodium calcium edetate for lead poisoning

Question 8

what specific antidotes may be used in a poisoned patient

Answer 8

acetylcysteine (or other glutathione precursor) - paracetamol overdose

naloxone - opiate antagonist

flumazenil - GABA antagonist used in benzodiazepine overdose