Poisons

Question 1

What needs to be asked when taking a history for poisoning?

Answer 1

Intentional or accidental?
What has been consumed?
How long ago?
How much?

Question 2

What are the general principles of management of poisoning?

Answer 2

ABCDE
Reduce absorption –> decontamination
Alter metabolism –> antidotes
Increase elimination –> kidneys

Question 3

Which investigations can be done for poisoning?

Answer 3

Test blood level of substance (only a few)
Associated pathology –> renal failure, rhabdomyolysis, hyperkalaemia
ABGs –> acid/base derangement, ventilatory failure
ECG

Question 4

Which substances can be tested for in the blood to confirm toxicity/guide therapy?

Answer 4

Paracetamol
Salicylates
Ethylene glycol
Lithium

Question 5

Why in an ECG useful and which important abnormality must be checked for?

Answer 5

May demonstrate signs of cardio toxicity and will guide management
–> QTc (increase risk of malignant arrhythmia)

Question 6

Which methods of gut decontamination can be used for certain toxins?

Answer 6

Activated charcoal
Bowel irrigation
(forced emesis not recommended)

Question 7

Where should you look for management of specific toxins?

Answer 7

Toxbase

Question 8

What is the antidote for paracetamol?

Answer 8

N-acetylcysteine

Methionine

Question 9

What is the antidote for tricyclic antidepressants?

Answer 9

Sodium bicarbonate

Question 10

What is the antidote for beta blockers?

Answer 10

Glucagon

Question 11

What is the antidote for ethylene glycol + methanol?

Answer 11

Ethanol

Fomepizole

Question 12

What is ethylene glycol?

Answer 12

Antifreeze

Question 13

What are the antidotes for cyanide?

Answer 13

Hydroxycobalamin
Sodium nitrate
Sodium thiosulphate

Question 14

What is the antidote for iron salts?

Answer 14

Desferrioxamine

Question 15

What is the antidote for opioids?

Answer 15

Naloxone

Question 16

What are the antidotes for organophosphates?

Answer 16

Atropine

Pralidoxime mesylate

Question 17

What are the methods of increasing elimination to treat poisoning?

Answer 17

Urinary alkalinisation
Haemodialysis
Haemofiltration

Question 18

Give an example of using urinary alkalinisation to treat poisoning

Answer 18

Treat aspirin overdose with sodium bicarbonate –> increases elimination via kidneys

Question 19

Give some examples of poisonings that can be treated with haemodialysis

Answer 19

Alcohols e.g. methanol
Lithium
Aspirin

Question 20

Which poisonings can be treated with haemofiltration?

Answer 20

Theophyllines

Carbamazepine

Question 21

How much paracetamol ingestion warrants referral to hospital for assessment?

Answer 21

> 75mg/kg

Question 22

How is paracetamol metabolised in therapeutic doses?

Answer 22

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

Question 23

What happens to paracetamol metabolism in paracetamol overdose?

Answer 23

Excess paracetamol –> more NAPQI
Hepatocellular supplies of glutathione become depleted + NAPQI remains in toxic form
–> widespread hepatocyte damage + death –> acute liver necrosis

Question 24

What are the initial features of paracetamol poisoning?

Answer 24

Nausea and vomiting –> extremely common

Very rarely –> coma + severe metabolic acidosis (extremely high plasma paracetamol)

Question 25

What are the later features of paracetamol poisoning?

Answer 25

In severe cases: - abdominal pain (12-36 hours) - hepatic necrosis after 2-3 days: RUQ pain + tenderness, N&V, jaundice, AKI, hepatic encephalopathy

Question 26

What are the indications for starting treatment for paracetamol poisoning?

Answer 26

Blood paracetamol levels checked at 4 hours + plotted on graph --> commence treatment if level is above line

Question 27

How quickly should treatment for paracetamol poisoning be started and what should be done if the patient presents late?

Answer 27

Should commence within 8 hours of ingestion If presentation delayed (>8 hours) start treatment and await blood results

Question 28

Which blood tests should be done following treatment for paracetamol overdose?

Answer 28

LFTs U&Es INR

Question 29

Which blood test is the most accurate indictor of synthetic liver function following paracetamol overdose?

Answer 29

INR

Question 30

How should the blood tests following paracetamol overdose treatment be interpreted?

Answer 30

If bloods normal --> treatment can be stopped | If bloods deranged --> N-acetyl cysteine treatment must be continued

Question 31

What is the antidote for benzodiazepines?

Answer 31

Flumazenil