Category 1

• Aetiology: Paracetamol poisoning:
• pH <7.25 more than 24 hours after overdose and after fluid resuscitation.

Category 2

• Aetiology: Paracetamol poisoning: Co-existing:
• Prothrombin time >100 seconds or INR >6.5, AND
• Serum creatinine >300 μmol/l or anuria, AND
• Grade 3–4 encephalopathy

Category 3

• Aetiology: Paracetamol poisoning:
• Significant liver injury and coagulopathy following exclusion of other causes of hyperlactatemia (e.g. pancreatitis, intestinal ischemia) after adequate fluid resuscitation.
• Arterial lactate >5 mmol/l on admission, AND
• Arterial lactate >4 mmol/l 24 hours later, AND
• Presence of clinical hepatic encephalopathy.

Category 4

• Aetiology: Paracetamol poisoning: Two of the following three criteria (category 2) AND clinical evidence of deterioration (e.g. increased ICP, FiO2 >50%, increasing inotrope requirements) in the ABSENCE of clinical sepsis.
• Prothrombin time >100 seconds or INR >6.5, AND
• Serum creatinine >300 μmol/l or anuria, AND
• Grade 3–4 encephalopathy

Category 5

• Aetiology: Favourable non-paracetamol aetiologies such as acute viral hepatitis or ecstasy/cocaine induced ALF:
• Clinical hepatic encephalopathy is mandatory AND
• Prothrombin time >100 seconds, or INR >6.5, OR
• Any three from the following:
• Age >40 or <10 years
• Prothrombin time >50 seconds or INR >3.5
• Any grade of hepatic encephalopathy with jaundice to encephalopathy time >7 days
• Serum bilirubin >300 μmol/l.

Category 6

• Aetiology: Unfavourable non-paracetamol aetiologies such as seronegative or idiosyncratic drug reactions:
• Prothrombin time >100 seconds, or INR >6.5, OR
• In the absence of clinical hepatic encephalopathy:
• INR >2 after vitamin K repletion is mandatory AND any two from:
• Age >40 or <10 years
• Prothrombin time >50 seconds or INR >3.5
• If hepatic encephalopathy is present then jaundice to encephalopathy time >7 days
• Serum bilirubin >300 μmol/l.

Category 7

• Aetiology: Acute presentation of Wilson’s disease, or Budd-Chiari syndrome.
• A combination of coagulopathy, and any grade of encephalopathy.

Category 8

• Hepatic artery thrombosis on days 0 to 21 after liver transplantation

Category 9

• Early graft dysfunction on days 0 to 7 after liver transplantation with at least two of the following:
• AST >10,000
• INR >3.0
• Arterial lactate >3 mmol/l
• Absence of bile production

Category 10

• The total absence of liver function (e.g. after total hepatectomy)

Category 11

• Any patient who has been a live liver donor (NHS entitled) who develops severe liver failure within 4 weeks of the donor operation

Category 20

• Acute liver failure in children under two years of age:
• INR >4 OR
• Grade 3-4 encephalopathy.