# Acute Liver Failure

## Definition

Acute liver failure is defined by the acute onset of hepatic dysfunction, manifest as an INR of 1.5 or greater combined with hepatic encephalopathy, in a patient without pre-existing liver disease, with a total illness duration of less than 26 weeks. This definition excludes patients with previously recognized chronic liver disease, in whom acute deterioration constitutes acute-on-chronic liver failure, a distinct entity with different prognostic and management implications.

Acute liver failure is further subclassified based on the interval between the onset of jaundice and the development of encephalopathy. Hyperacute liver failure, developing within 7 days, is most commonly caused by acetaminophen overdose and ischemic hepatitis and paradoxically carries the best prognosis with medical management alone, as the rapid onset allows less time for hepatocyte loss and often preserves regenerative capacity. Acute liver failure, developing over 7 to 21 days, is associated with viral hepatitis and drug reactions and carries an intermediate prognosis. Subacute liver failure, developing over 21 days to 26 weeks, is associated with autoimmune hepatitis, drug-induced liver injury, Wilson disease, and indeterminate etiologies, and carries the worst prognosis without transplantation, as the prolonged course reflects exhaustion of hepatocyte regenerative capacity.

## Etiology

### Developed Countries (US/Europe)

| Etiology | Frequency (US) | Prognosis Without Transplant | Key Features |
|---|---|---|---|
| Acetaminophen | 40-50% | Best (65-70% spontaneous survival) | Intentional or unintentional; NAC is antidote |
| Drug-induced (idiosyncratic) | 10-15% | Intermediate | Amoxicillin-clavulanate, isoniazid, supplements |
| Viral hepatitis | 5-10% | Variable | HBV > HAV > HEV; HCV virtually never |
| Autoimmune hepatitis | 5-10% | Poor without treatment | Autoantibodies may be negative; corticosteroid trial |
| Ischemic hepatopathy | 5-10% | Good if hemodynamics corrected | AST/ALT often >5000; rapid rise and fall |
| Wilson disease | Rare | Fatal without transplant (~0% spontaneous survival) | Coombs-negative hemolysis, low ALP:bilirubin <4 |
| Budd-Chiari | Rare | Variable | Hepatic vein thrombosis |
| Indeterminate | 15-20% | Worst | No cause identified; worst spontaneous survival |

Acetaminophen overdose is the most common cause of acute liver failure in the United States, accounting for 40 to 50% of cases. It carries the best prognosis among all etiologies, with a spontaneous survival rate of 65 to 70%. Both intentional overdose and unintentional therapeutic misadventure occur, with the latter often involving the combination of chronic alcohol use or fasting states that deplete hepatic glutathione reserves, rendering the liver susceptible to acetaminophen toxicity at lower doses.

Drug-induced liver injury accounts for 10 to 15% of cases and is typically idiosyncratic in nature. Implicated agents include antibiotics (amoxicillin-clavulanate, isoniazid, trimethoprim-sulfamethoxazole), anticonvulsants, and herbal and dietary supplements (green tea extract, Herbalife products), as well as nonsteroidal anti-inflammatory drugs.

Viral hepatitis causes acute liver failure less commonly in developed countries. Hepatitis A is rare in this setting, while hepatitis B may present as acute infection or reactivation in immunocompromised patients. Hepatitis E is increasingly recognized, particularly in pregnant women and immunocompromised individuals. Hepatitis C virtually never causes acute liver failure.

Autoimmune hepatitis accounts for 5 to 10% of acute liver failure and is particularly important to identify early, as a corticosteroid trial may avert the need for transplantation. In the acute setting, autoantibodies may be negative (seronegative presentation), creating diagnostic difficulty. Ischemic hepatopathy, or shock liver, accounts for 5 to 10% of cases and is characterized by markedly elevated aminotransferases often exceeding 5000 IU/L, with rapid rise and equally rapid decline. It typically occurs in critically ill patients following cardiac arrest, cardiogenic shock, or severe sepsis, and resolves if the underlying hemodynamic insult is corrected.

Budd-Chiari syndrome, resulting from hepatic vein thrombosis, can present acutely with fulminant liver failure in severe cases. Wilson disease presenting as acute Wilsonian crisis is characterized by the combination of acute liver failure and Coombs-negative hemolytic anemia, very low alkaline phosphatase (with an alkaline phosphatase-to-bilirubin ratio below 4), low ceruloplasmin, and elevated 24-hour urine copper. This presentation is almost uniformly fatal without liver transplantation, and the Wilsonian ALF score helps identify the need for urgent transplant listing.

Pregnancy-related causes include acute fatty liver of pregnancy and HELLP syndrome, for which delivery is the definitive treatment. Indeterminate etiology, in which no cause is identified despite thorough evaluation, accounts for 15 to 20% of cases and represents the category with the worst spontaneous survival.

### Developing Countries

In the developing world, viral hepatitis (hepatitis A, B, and E) predominates as the cause of acute liver failure. Hepatitis E is particularly dangerous in pregnancy, carrying a mortality rate of 20 to 25%.

## Initial Evaluation

### Etiologic Workup (Rapid, Systematic)

The etiologic evaluation in acute liver failure must be performed rapidly and systematically, as determining the cause directly influences management and prognosis. Acetaminophen level should be measured immediately and the Rumack-Matthew nomogram applied for timed ingestions, while N-acetylcysteine therapy is initiated empirically. Comprehensive viral serologies should include hepatitis A IgM, hepatitis B surface antigen, hepatitis B core IgM, HCV RNA, hepatitis E IgM and RNA, and PCR testing for herpes simplex virus, cytomegalovirus, and varicella-zoster virus.

Autoimmune markers including ANA, anti-smooth muscle antibody, IgG level, and anti-LKM1 should be obtained. Wilson disease screening requires ceruloplasmin, serum copper, 24-hour urine copper, the alkaline phosphatase-to-bilirubin ratio, and a Coombs test. A thorough medication history including all over-the-counter medications, supplements, and herbal products is essential, along with a toxicology screen. Doppler ultrasound of the liver evaluates hepatic vein patency (to exclude Budd-Chiari syndrome), portal vein patency, and liver echotexture. A pregnancy test and echocardiography (to assess for ischemic hepatopathy and right heart failure) complete the initial evaluation.

### Laboratory Monitoring

Serial laboratory monitoring includes complete blood count, comprehensive metabolic panel (electrolytes, glucose, and renal function), liver function tests, INR and prothrombin time, fibrinogen, lactate, arterial ammonia, arterial blood gas, and phosphorus. Factor V level serves as an important prognostic marker in some European systems (Clichy criteria), where levels below 20% in patients younger than 30 or below 30% in patients older than 30, combined with grade III-IV hepatic encephalopathy, indicate the need for transplantation.

<image>An etiologic evaluation checklist and management pathway for acute liver failure. Start with "ALF diagnosed: INR >= 1.5 + encephalopathy + no prior liver disease + < 26 weeks duration." Two parallel pathways: Left "Rapid Etiologic Workup" with a checklist format: APAP level + NAC (start empirically), viral panel (HAV IgM, HBsAg, anti-HBc IgM, HEV IgM, HSV PCR), autoimmune panel (ANA, ASMA, IgG, anti-LKM1), Wilson screen (ceruloplasmin, ALP:bilirubin ratio < 4, Coombs test), toxicology screen + medication review, liver Doppler US, pregnancy test, echocardiogram. Right "Critical Management": ICU admission, NAC (empirically for all until APAP ruled out), intracranial pressure monitoring considerations, glucose monitoring (hypoglycemia common), coagulopathy management (FFP only for procedures, NOT for INR correction), infection surveillance (blood/urine cultures), renal replacement therapy if AKI, early transplant center notification. Bottom: "Prognostic Assessment" with King's College Criteria boxes: APAP pathway (pH < 7.3 after resuscitation OR all three: INR > 6.5 + Cr > 3.4 + Grade III-IV HE) and Non-APAP pathway (INR > 6.5 OR any three of: age < 10 or > 40, etiology indeterminate/drug, jaundice > 7 days before HE, INR > 3.5, bilirubin > 17.5). Use red for urgent actions, yellow for monitoring, blue for etiologic workup.</image>

## Management

### General ICU Care

Early transfer to a liver transplant center is of paramount importance and should be initiated before clinical deterioration whenever possible. ICU admission is indicated for all patients with grade II or greater hepatic encephalopathy. The coordinated involvement of hepatology, critical care, transplant surgery, and nephrology teams is essential for optimal outcomes.

### N-Acetylcysteine (NAC)

For acetaminophen overdose, NAC is the standard of care and is most effective when administered within 8 hours of ingestion, though it retains benefit even beyond 24 hours. The intravenous protocol administers 150 mg/kg over 1 hour, followed by 50 mg/kg over 4 hours, and then 100 mg/kg over 16 hours (21-hour protocol). NAC infusion should continue until the INR is trending downward, the acetaminophen level is undetectable, and the patient is clinically improving. The oral protocol uses a 140 mg/kg loading dose followed by 70 mg/kg every 4 hours for 17 additional doses (72-hour protocol).

For non-acetaminophen acute liver failure, intravenous NAC is also beneficial. The Lee trial (2009) demonstrated improved transplant-free survival in patients with grades I-II encephalopathy, though no benefit was observed in patients with grades III-IV encephalopathy. NAC should be considered for all patients with non-acetaminophen acute liver failure who present with early encephalopathy.

### Cerebral Edema and Intracranial Hypertension

Cerebral edema with intracranial hypertension is the leading cause of death in acute liver failure, accounting for 20 to 25% of deaths. The risk correlates with arterial ammonia levels, with values exceeding 150 micromol/L conferring high risk, and with hepatic encephalopathy grade, with the highest risk in grades III-IV.

Monitoring approaches include intracranial pressure monitoring, which is employed at some centers though it remains controversial due to the risk of hemorrhagic complications. Transcranial Doppler, optic nerve sheath diameter measurement on bedside ultrasound, and serial pupillary examination serve as non-invasive surrogates. The management targets are maintaining ICP below 20 to 25 mmHg and cerebral perfusion pressure (MAP minus ICP) above 60 mmHg.

Treatment of elevated intracranial pressure begins with the head of bed elevated to 30 degrees, minimizing stimulation, and avoiding fever. Hypertonic saline (3% NaCl infusion) to maintain serum sodium at 145 to 155 mEq/L serves as prophylactic hypernatremia therapy and reduces the risk of cerebral edema. Mannitol at 0.5 to 1 g/kg intravenously is used for acute ICP crises, though it should be avoided in patients with renal failure and requires monitoring of the osmolar gap. Mild therapeutic hypothermia to 33 to 35 degrees Celsius has shown reduction in cerebral edema in case series, though it has not been validated in randomized controlled trials; some centers employ it prophylactically.

### Coagulopathy Management

The INR is a critical prognostic marker in acute liver failure, and it is essential that clinicians resist the impulse to correct it with fresh frozen plasma or factor concentrates unless the patient has active bleeding or requires an invasive procedure. Correcting the INR masks the most important prognostic indicator and is therapeutically futile, as consumed factors are rapidly depleted again.

A paradox of acute liver failure coagulopathy is that despite markedly elevated INR values, patients frequently have balanced hemostasis because both procoagulant and anticoagulant factor levels are proportionally decreased. Thromboelastography and rotational thromboelastometry may demonstrate normal clot formation despite alarming INR values. Vitamin K 10 mg intravenously should be administered empirically to correct any nutritional deficiency component, though it will not fully correct synthetic dysfunction. Platelet transfusion is reserved for platelet counts below 50,000 with a planned procedure or active bleeding. Recombinant factor VIIa is not recommended routinely due to thrombotic complications.

### Infection

Infection is exceedingly common in acute liver failure, with approximately 80% of patients developing bacterial and/or fungal infections during their course. Systemic inflammatory response syndrome criteria are unreliable in this setting, as patients may manifest SIRS without underlying infection. Surveillance cultures of blood, urine, and sputum should be obtained every 48 to 72 hours. A low threshold for initiating empiric antibiotics is appropriate, and many centers use prophylactic antibiotics in patients with grade III-IV encephalopathy. Antifungal agents should be considered in patients who fail to improve on antibacterial therapy.

### Metabolic Management

Hypoglycemia is a common and dangerous complication resulting from impaired hepatic gluconeogenesis and requires continuous glucose monitoring with dextrose infusions (D10W). Metabolic acidosis, typically lactic acidosis from hepatic failure and tissue hypoperfusion, should be managed by correcting the underlying cause. Hypokalemia, hypophosphatemia, and hypomagnesemia are frequent and require aggressive monitoring and replacement.

Acute kidney injury develops in 30 to 70% of patients with acute liver failure. Continuous renal replacement therapy is preferred over intermittent hemodialysis, as it provides more hemodynamically stable fluid removal and better management of cerebral edema by avoiding rapid osmotic shifts.

## Prognostic Assessment and Transplant Decision

### King's College Criteria (Most Widely Used)

#### APAP-Induced ALF

For acetaminophen-induced acute liver failure, liver transplantation is indicated when arterial or venous pH is below 7.30 after adequate fluid resuscitation, regardless of hepatic encephalopathy grade. Alternatively, transplantation is indicated when all three of the following are present: INR exceeding 6.5, serum creatinine exceeding 3.4 mg/dL, and grade III-IV hepatic encephalopathy. The positive predictive value of these criteria ranges from 79 to 93%, with a negative predictive value of 74 to 97%.

#### Non-APAP ALF

For non-acetaminophen acute liver failure, transplantation is indicated when the INR exceeds 6.5 regardless of encephalopathy grade. Alternatively, transplantation is indicated when any 3 of the following 5 criteria are present: age below 10 or above 40, etiology is indeterminate or drug-related, duration of jaundice exceeds 7 days before encephalopathy onset, INR exceeds 3.5, or bilirubin exceeds 17.5 mg/dL. The positive predictive value is lower for non-acetaminophen criteria compared with the acetaminophen criteria.

### Other Prognostic Models

The Clichy criteria, primarily used in France, incorporate factor V level and hepatic encephalopathy grade. The MELD score correlates with prognosis but was not specifically designed for acute liver failure; a MELD exceeding 30 is associated with poor spontaneous survival. The Acute Liver Failure Study Group prognostic index incorporates etiology, coma grade, INR, bilirubin, phosphorus, and vasopressor use, and may outperform King's College Criteria.

Dynamic markers provide important supplementary prognostic information. Arterial ammonia exceeding 150 micromol/L predicts cerebral edema and death. Arterial lactate exceeding 3.5 mmol/L after fluid resuscitation in acetaminophen-related acute liver failure has good sensitivity and specificity for poor prognosis, as demonstrated by Bernal and colleagues. Rising serum phosphorus in acetaminophen-related acute liver failure indicates impaired hepatic regeneration and portends a poor prognosis.

### Transplant Listing

UNOS Status 1A provides the highest priority listing for acute liver failure. Absolute contraindications to transplantation include uncontrolled sepsis, severe and uncorrectable cardiopulmonary disease, irreversible brain injury (fixed dilated pupils for more than 24 hours), active substance abuse without appropriate assessment, and extrahepatic malignancy.

## Etiology-Specific Considerations

### Acute Wilsonian Crisis

Acute Wilsonian crisis presenting as liver failure is rapidly fatal without transplantation, with essentially 0% spontaneous survival. Coombs-negative hemolytic anemia in combination with acute liver failure is highly suggestive of this diagnosis. The Wilsonian ALF prognostic index incorporates bilirubin, INR, AST, white blood cell count, and albumin; a score of 11 or greater indicates the need for transplantation. Temporizing measures include plasmapheresis or the Molecular Adsorbent Recirculating System to remove circulating copper while bridging to transplantation.

### Herpes Simplex Hepatitis

Herpes simplex hepatitis is rare but rapidly fatal if untreated, occurring predominantly in immunocompromised or pregnant patients. It is characterized by very high aminotransferase levels, an anicteric presentation in many cases, and vesicular rash in only 50% of patients. Empiric acyclovir at 10 mg/kg intravenously every 8 hours should be initiated in any immunocompromised patient presenting with acute liver failure, even before HSV PCR results are available.

### Amanita phalloides (Mushroom Poisoning)

Alpha-amanitin, the toxin of Amanita phalloides, inhibits RNA polymerase II and presents with a characteristic triphasic clinical course: gastrointestinal symptoms at 6 to 12 hours, apparent clinical improvement, and then hepatic failure at 48 to 72 hours. Treatment includes intravenous penicillin G, intravenous NAC, and silibinin (a milk thistle derivative) where available. Liver transplantation is required for severe cases.

<image>A prognostic scoring comparison table for acute liver failure. Create a side-by-side comparison of three prognostic systems. Left panel "King's College Criteria — APAP": list criteria with checkboxes (pH < 7.30 after resuscitation; OR INR > 6.5 + Cr > 3.4 + Grade III-IV HE — all three required). Center panel "King's College Criteria — Non-APAP": list criteria (INR > 6.5 alone; OR any 3 of 5: age < 10 or > 40, etiology indeterminate/drug, jaundice > 7 days before HE, INR > 3.5, bilirubin > 17.5). Right panel "Dynamic Markers": list arterial ammonia (> 150 umol/L = cerebral edema risk), arterial lactate (> 3.5 = poor prognosis in APAP), phosphorus (rising = impaired regeneration), factor V (< 20-30% = poor prognosis). Include PPV/NPV statistics for each system. Below all panels, add a "Transplant Decision" box: "Meeting transplant criteria -> UNOS Status 1A listing. Contraindications: uncontrolled sepsis, irreversible brain injury, severe cardiopulmonary disease." Use red gradient for worse prognosis indicators, green for favorable markers (low ammonia, improving INR/lactate). Include a note: "NAC improves transplant-free survival in early (grade I-II) non-APAP ALF — administer empirically."</image>

## Key Clinical Pearls

- NAC should be started empirically for all cases of acute liver failure until acetaminophen toxicity is ruled out. NAC is also beneficial in non-acetaminophen acute liver failure with early encephalopathy (Lee trial).
- The INR must not be corrected with FFP to "improve coagulopathy." This masks the most important prognostic marker. Correction is reserved for active bleeding or procedures.
- Arterial ammonia exceeding 150 micromol/L predicts intracranial hypertension. Prophylactic hypertonic saline to maintain sodium at 145 to 155 mEq/L is recommended.
- King's College Criteria remain the most widely used prognostic tool. Arterial lactate exceeding 3.5 mmol/L in acetaminophen-related acute liver failure adds prognostic information.
- Transfer to a liver transplant center should occur early, before clinical deterioration. UNOS Status 1A provides the highest transplant priority.
- Wilson disease presenting as acute liver failure is almost universally fatal without transplant. Coombs-negative hemolytic anemia with low alkaline phosphatase-to-bilirubin ratio (below 4) should prompt urgent evaluation.
- HSV hepatitis should be considered and treated empirically with acyclovir in immunocompromised patients with acute liver failure, even without vesicular rash.
- Rising serum phosphorus in acetaminophen-related acute liver failure indicates impaired hepatic regeneration and poor prognosis.

## References
1. Lee WM, et al. AASLD Position Paper: The management of acute liver failure: Update 2011. *Hepatology*. 2012;55(3):965-967.
2. Lee WM, et al. Intravenous N-acetylcysteine improves transplant-free survival in early stage non-acetaminophen acute liver failure. *Gastroenterology*. 2009;137(3):856-864.
3. O'Grady JG, et al. Early indicators of prognosis in fulminant hepatic failure. *Gastroenterology*. 1989;97(2):439-445.
4. Bernal W, et al. Blood lactate as an early predictor of outcome in paracetamol-induced acute liver failure. *Lancet*. 2002;359(9306):558-563.
5. Stravitz RT, Lee WM. Acute liver failure. *Lancet*. 2019;394(10201):869-881.