*Paracetamol overdose

Question 1

If paracetamol level is below treatment line, what is the only situation in which you would treat anyway?

Answer 1

If the overdose was staggered

Question 2

What assessment is required for all patients suspected of taking an overdose?

Answer 2

Psych

Question 3

Is death after overdose common?

Answer 3

No - rare and reduced further by good A-E assessment

Question 4

By how many hours will most overdoses have stabilised?

Answer 4

12hrs

Question 5

What should you clarify about overdose in the history?

Answer 5

• agent(s)
• date and time ingested
• quantity ingested
• route
• single or staggered overdose

Question 6

What is the pathophysiology of paracetamol overdose?

Answer 6

Paracetamol is broken down into toxic metabolite NAPQI by liver CYP2EI
NAPQI is usually inactivated quickly by glutathione but this is rapidly consumed in overdose

Question 7

What is the clinical progression of paracetamol overdose?

Answer 7

1. Initially asymptomatic
2. Nausea, vomiting, RUQ pain
3. Increase in ALT/AST and PT
4. Hepatic necrosis and finally fulminant liver failure

Question 8

With what dose of paracetamol should you be concerned in overdose?

Answer 8

> 12g or >150mg/kg taken

toxic dose is 75mg/kg - urgently assess and take bloods 4hrs post-dose

Question 9

Why is it important to know what time the paracetamol was taken?

Answer 9

For the nomogram

Question 9

Why is it important to know if the dose was staggered for paracetamol overdose?

Answer 9

Start NAC if staggered dose

Question 10

What is the NAC regimen?

Answer 10

First infusion - loading dose 150mg/kg over 1hr
Second infusion - 50mg/kg over 4hrs
Third infusion - 100mg/kg over 16hrs

Question 11

What investigations are required after the third NAC infusion?

Answer 11

Recheck U&Es, LFTs, clotting

ALT/AST and INR/PT are the most important markers

Question 12

What is the transplant referral criteria for paracetamol overdose?

Answer 12

1. pH < 7.3* after volume resus
2. • > 24hrs post-ingestion

OR

1. PT > 100* *
2. • creatinine >300mcmol/L
3. • grade III/IV encephalopathy within 24hrs

• • • or arterial lactate >3.5mmol/L after early fluid resus
• • *- INR >6.5

Question 13

Patient presents 6 hours after taking 28 500mg tablets of paracetamol. She regrets her actions. The initial paracetamol level is 220. Initial FBC, U+E, LFT and clotting are normal. What should you do?
* A Declare patient medically fit and refer to psychiatry
* B Start maintenance dose of NAC over 16 hours
* C Start iv fluids. Observe for 24 hours and repeat bloods
* D Load with NAC, followed by maintenance infusion

Answer 13

D

Question 14

Patient is loaded with NAC and she has completed her 16 hour maintenance. Her bloods show creat 120, INR 1.5 and ALT 400. What should you do?
* A reload with NAC
* B stop the infusion and refer to psychiatry
* C continue maintenance infusion for further 16 hours
* D Refer to Liver ITU

Answer 14

C

If there is evidence of liver toxicity at the end of the 21-hour acetylcysteine infusion:
* Continue acetylcysteine at the dose and infusion rate used in the third treatment bag.
* Re-check urea and electrolytes, creatinine, ALT, and INR every 10 to 16 hours to assess the course of liver injury.
* This allows early assessment of liver toxicity progression

Question 15

Patient continues to deteriorate. Which of the following would be an indication to refer to a Liver ITU at Day 2?
* A INR 2.8
* B RUQ pain
* C creat 180
* D persistent hypoglycaemia
* E ALT 900

Answer 15

D

Question 16

When should you consider activated charcoal in paracetamol overdose?

Answer 16

Only if the patient presents within 1hr of overdose, otherwise wait until 4hrs to take a VBG - plasma conc measured earlier than this cannot be interpreted

Question 17

What is the main side-effect associated with acetylcysteine?

Answer 17

anapylactoid reactions - associated with up to 30% of infusions

Question 18

How do you manage reactions to acetycysteine?

Answer 18

Consider H1 antagonist and salbutamol nebs then you must restart the infusion .

Question 19

What are the criteria for discharge after paracetamol overdose bloods post 21hr NAC?

Answer 19

If all blood results meet the following criteria:

• INR is 1.3 or less AND
• ALT is < x2 upper limit of normal AND
• ALT is < x2 the admission measurement

=> the patient can be discharged safely.

Question 20

What should you do if the 21hrs post-NAC bloods are abnormal?

Answer 20

If blood results are abnormal:

• the ALT has more than doubled since the admission measurement, OR
• the ALT is two times the upper limit of normal or more, OR
• the INR is greater than 1.3 (in the absence of another cause, e.g. warfarin)

=> continue NAC and repeat all blood tests in a further 8-16 hours.