Paracetamol OD

Question 1

What is the aeitology of paracetmol OD?

Answer 1

• Most common deliberate overdose

- Usually, 500mg tablets

Question 2

What is a OD on paracetmol for levels?

Answer 2

OD> 150mg/kg, 12g can be fatal

Question 3

What are DDx for paracetamol OD?

Answer 3

1. Hep A/B

2. Ischaemic Hepatitis

Question 4

What is the presentation <24hr?

Answer 4

1. Patients are often asymptomatic

2. Mild N&V and lethargy

Question 5

What is the presentation 24-72hr?

Answer 5

1. RUQ pain
2. Vomiting
3. Hepatomegaly

Question 6

What is the presentation >72hr?

Answer 6

Acute Liver failure (jaundice)

Question 7

What bedside+lab investigations are done?

Answer 7

1. ABG
2. Urinalysis
3. Serum paracetmol conc
4. LFts
5. Prothombin time/INR
6. Blood glucose
7. U+Es
8. FBC

Question 8

Why do you do ABG?

Answer 8

lactic acidosis – bad sign!

Question 9

What can urinalysis show?

Answer 9

if haematuria or proteinuria present, may indicate kidney failure

Question 10

Why do you do serum paracetamol concentation?

Answer 10

risk stratify likelihood of liver injury and determine whether treatment with acetylcysteine is necessary

Question 11

Why do you do LFTs?

Answer 11

1. check hepatic dysfunction

2. high ALT

Question 12

Why do you do prothrombin time/ INR?

Answer 12

elevated, hepatic dysfunction

Question 13

Why do you do blood glucose?

Answer 13

hypoglycaemia indicates liver injury

Question 14

Why are U+Es done?

Answer 14

raised creatinine, indicates acute kidney injury (and/or liver injury)

Question 15

What would FBC show?

Answer 15

1. leukocyotsis
2. anaemia
3. thrombocytopenia

Question 16

What is the management of paracetemol OD?

Answer 16

1. IV N-acetylcysteine

2. Liver transplant

Question 17

What is excess paracetamol metabolised by and what into?

Answer 17

metabolized by cytochrome P450 enzymes into NAPQI

Question 18

What does NAPQI usually do?

Answer 18

combines with intracellular glutathione and is detoxified

Question 19

What happens to NAPQI in OD?

Answer 19

1. excess NAPQI exceeds capacity to detoxify 2. excess NAPQI binds to cellular components 3. causes mitochondrial injury, therefore causing death of heapatocyte

Question 20

When would lactic acidosis show up in paracetmol OD?

Answer 20

1. Early after large paracetamol ingestion – this is a bad sign, it is often associated with a coma
2. Later after liver failure has already developed, high predictor of mortality

Question 21

Why can paracetmol OD be hard to treat?

Answer 21

• often asymptomatic and that as shown in the diagram, the longer they wait, the lower the detectable level of paracetamol in their blood
• so might not come in until it is too late for them to be treated by N-Acetylcysteine so they need to be put onto the list for liver transplant