Paracetamol overdose

Question 1

what is depleted in paraceatmol overdose

Answer 1

glutathione

Question 2

what is a single acute overdose

Answer 2

defined as <1hr

Question 3

what liver enzymes may be raised in paracetamol overdose

Answer 3

AST

ALT

Question 4

what might you see on ABG

Answer 4

acidaemia

raised lactate

Question 5

what happens to the prothrombin time and INR

Answer 5

both elevated

Question 6

what investigations should you do

Answer 6

serum paracetamol
LFT
U&E
clotting screen
ABG/VBG

Question 7

how do you manage an acute single overdose up to 8 hours

Answer 7

check 4 hour paracetamol conc

treat according to normogram

wait for 8 hour paracetamol levels

Question 8

how do you manage acute single overdose from 8-24hrs

Answer 8

NAC immediately if more than 150mg/kg ingested

Check bloods

NAC may be discontinued if the patient is thought not to be at risk

Question 9

how do you manage acute single overdose presenting >24h

Answer 9

NAC immediately if jaundiced or hepatic tenderness

otherwise wait for blood results and treat if abnormal

detectable level >24h suggests very large overdose –> treat

Question 10

what is the treatment for paracetamol overdose

Answer 10

N-Acetylcysteine

Question 11

how does NAC work

Answer 11

replenishes glutathione

Question 12

what should you do if there is a reaction to NAC

Answer 12

temporarily stop treatment

give antihistamines, bronchodilators, adrenaline

RESTART NAC

Question 13

in a staggered overdose what amount is unlikely to be toxic

Answer 13

<75mg/kg

Question 14

how should you manage staggered overdose

Answer 14

start NAC immediately

Question 15

when should you check the paracetamol level in staggered overdose and what should this guide

Answer 15

4hrs after last ingestion

can stop NAC if no detectable levels of paracetamol and no signs of hepatotoxicity

Question 16

what is the most serious complication of paracetamol overdose

Answer 16

liver injury leading to fulminant liver failure

Question 17

what should guide you to continue NAC even if paracetamol levels are normal

Answer 17

ALT more than doubled since admission

ALT more than twice upper normal limit

INR >1.3

Question 18

what are the clinical features of paracetamol overdose

Answer 18

attempted self harm

asymptomatic presentation

nausea/vomiting/abdo pain

RUQ pain and tenderness

less common: jaundice/confusion/decreased conscious level/asterixis

Question 19

what pathway becomes important in paracetamol overdose

Answer 19

oxidation by cytochrome P450 enzymes