What is the definition and criteria for liver failure?

Definition and Criteria for Liver Failure

Liver failure is defined as evidence of coagulation abnormality (usually INR ≥ 1.5) and any degree of mental alteration (encephalopathy) in a patient without preexisting cirrhosis and with an illness duration of less than 26 weeks. 1

Types of Liver Failure

Acute Liver Failure (ALF)

• Definition: Hepatic encephalopathy and coagulopathy (INR ≥ 1.5) developing within 26 weeks in a patient without preexisting liver disease 1
• Severity classification:
  • Severe ALF: PT ratio less than 50% 1
  • Serious ALF: PT ratio less than 50% with encephalopathy 1

Acute-on-Chronic Liver Failure (ACLF)

• Definition: Requires all of the following components 1:
  1. Acute onset with rapid deterioration in clinical condition
  2. Presence of liver failure defined by elevated bilirubin and elevated INR in patients with chronic liver disease with or without cirrhosis
  3. Presence of at least one extrahepatic (neurologic, circulatory, respiratory, or renal) organ failure

Diagnostic Criteria for Acute Liver Failure

Essential Criteria

• INR ≥ 1.5 (or PT prolonged by 4-6 seconds or more) 1
• Any degree of hepatic encephalopathy 1
• Absence of preexisting cirrhosis (with exceptions for Wilson disease, vertically-acquired HBV, or autoimmune hepatitis if recognized for <26 weeks) 1
• Illness duration less than 26 weeks 1

Initial Laboratory Evaluation

1. Coagulation studies:

   • Prothrombin time/INR
   • Factor V levels

2. Liver function tests:

   • AST, ALT, alkaline phosphatase, GGT
   • Total bilirubin
   • Albumin

3. Metabolic parameters:

   • Glucose
   • Electrolytes (sodium, potassium, chloride, bicarbonate)
   • Calcium, magnesium, phosphate

4. Other essential tests:

   • Arterial blood gas and lactate level
   • Arterial ammonia
   • Complete blood count

Etiological Workup for Liver Failure

Required Investigations 1

• Toxicology:

  • Serum acetaminophen levels
  • Urine toxicology screen (amphetamine, cocaine)

• Viral hepatitis markers:

  • Hepatitis A (IgM VHA)
  • Hepatitis B (HBsAg and anti-HBc IgM)

• Imaging:

  • Hepatic Doppler ultrasound
  • Echocardiography

Assessment of Disease Severity

Organ System Evaluation

1. Neurological assessment:

   • Grade of encephalopathy
   • Need for frequent monitoring of mental status

2. Cardiovascular assessment:

   • Hemodynamic status
   • Need for vasopressor support

3. Renal function:

   • Presence of acute kidney injury
   • Need for renal replacement therapy

Management Considerations

Immediate Actions

• Hospital admission is mandatory once ALF is diagnosed 1
• Early transfer to ICU is preferred due to rapid progression potential 1
• Early contact with a transplant unit for severe cases 1

Specific Treatments

• N-acetylcysteine administration regardless of suspected etiology 1
• Acyclovir if Herpes simplex virus hepatitis is suspected 1

Common Pitfalls to Avoid

1. Misdiagnosis: Failing to distinguish between acute liver failure and acute-on-chronic liver failure, which have different management implications and prognostic criteria 1

2. Delayed recognition: Not promptly identifying subtle alterations in mentation, which can progress rapidly hour-by-hour 1

3. Incomplete workup: Failing to perform comprehensive etiological investigations, as the cause significantly affects management and prognosis 1

4. Overlooking pre-existing liver disease: Not thoroughly evaluating for signs of cirrhosis, which would change the diagnosis from ALF to ACLF 1

5. Delayed ICU transfer: Not recognizing the potential for rapid deterioration requiring intensive monitoring and support 1

By adhering to these standardized definitions and criteria, clinicians can ensure prompt recognition, appropriate classification, and optimal management of liver failure, which is critical for improving patient outcomes in this high-mortality condition.