What is Acute Hepatic Failure?

Acute Hepatic Failure (AHF), also called Pediatric Acute Liver Failure (PALF), is a rapidly progressive liver dysfunction occurring in a child without pre-existing chronic liver disease, leading to severe impairment of liver synthetic function and encephalopathy.

It is a medical emergency associated with:

• Massive hepatocellular injury
• Coagulopathy
• Hepatic encephalopathy
• Multi-organ dysfunction
• High mortality without timely management or liver transplantation

According to major pediatric references including AAP, Nelson Textbook of Pediatrics, and ISPGHAN, early recognition and aggressive supportive care are critical for survival.

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Definition of Pediatric Acute Liver Failure

Pediatric acute liver failure is defined by:

Essential Criteria

• No evidence of chronic liver disease
• Acute liver injury
• Coagulopathy not corrected by vitamin K

Coagulation Criteria

• INR >1.5 with encephalopathy
  OR
• INR >2 without encephalopathy

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Why Acute Hepatic Failure is Dangerous

The liver performs critical functions:

• Glucose regulation
• Protein synthesis
• Clotting factor production
• Ammonia detoxification
• Drug metabolism
• Immune regulation

When the liver suddenly fails:

• Toxins accumulate
• Cerebral edema develops
• Severe bleeding can occur
• Shock and renal failure may follow

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Epidemiology of Pediatric Acute Liver Failure

• Rare but life-threatening condition
• Significant cause of PICU admissions
• Common indication for pediatric liver transplantation
• Mortality remains high despite advances

Common Age Groups

• Infants: metabolic and viral causes
• Older children/adolescents: drugs, autoimmune hepatitis, Wilson disease

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Etiology of Acute Hepatic Failure in Children

1. Viral Hepatitis

Common Viral Causes

• Hepatitis A
• Hepatitis B
• Hepatitis E
• HSV (especially neonates)
• EBV
• CMV
• Adenovirus
• Enteroviruses

Important Point

In developing countries including Nepal and South Asia:

• Hepatitis A and E remain major causes

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2. Drug-Induced Liver Injury (DILI)

Common Drugs

• Acetaminophen (Paracetamol)
• Antitubercular drugs
• Valproate
• Antiepileptics
• Herbal medications

Acetaminophen Toxicity

Most common cause in many developed countries.

Toxic metabolite:

• NAPQI

Normally detoxified by glutathione.

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3. Metabolic Disorders

Especially important in infants.

Major Causes

• Galactosemia
• Tyrosinemia
• Mitochondrial disorders
• Fatty acid oxidation defects
• Wilson disease
• Neonatal hemochromatosis

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4. Autoimmune Hepatitis

Can present dramatically with:

• Jaundice
• Coagulopathy
• Encephalopathy

Look for:

• ANA
• ASMA
• Elevated IgG

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5. Ischemic and Toxic Causes

• Shock liver
• Sepsis
• Mushroom poisoning
• Toxins

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6. Indeterminate Causes

A substantial number of pediatric cases remain unexplained despite extensive workup.

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Pathophysiology of Acute Hepatic Failure

Hepatocyte Injury

Massive hepatocyte necrosis leads to:

• Failure of detoxification
• Reduced clotting factor synthesis
• Metabolic instability

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Hyperammonemia

Ammonia accumulates due to impaired hepatic detoxification.

This causes:

• Astrocyte swelling
• Cerebral edema
• Increased intracranial pressure

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Coagulopathy

Liver cannot synthesize:

• Factors II
• V
• VII
• IX
• X

Result:

• Severe bleeding tendency

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Immune Dysfunction

Patients become highly susceptible to:

• Sepsis
• Fungal infections

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Clinical Features of Acute Hepatic Failure

Early Symptoms

• Nausea
• Vomiting
• Malaise
• Fever
• Abdominal pain
• Poor feeding
• Irritability

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Liver-Specific Findings

• Jaundice
• Hepatomegaly
• Tender liver
• Dark urine
• Pale stools

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Features of Hepatic Encephalopathy

Stage I

• Irritability
• Sleep disturbances
• Behavioral changes

Stage II

• Confusion
• Drowsiness
• Asterixis

Stage III

• Stupor
• Hyperreflexia

Stage IV

• Coma

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Signs of Cerebral Edema

• Hypertension
• Bradycardia
• Unequal pupils
• Abnormal posturing

This is a life-threatening emergency.

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Diagnostic Evaluation of Acute Hepatic Failure

Initial Laboratory Workup

Liver Function Tests

• AST/ALT
• Bilirubin
• Albumin
• ALP
• GGT

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Synthetic Function

• PT/INR
• Fibrinogen

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Metabolic Evaluation

• Blood glucose
• Lactate
• Serum ammonia
• ABG

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Viral Studies

• HAV IgM
• HBsAg
• Anti-HBc IgM
• HEV serology
• HSV PCR

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Autoimmune Tests

• ANA
• ASMA
• Anti-LKM
• IgG

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Metabolic Tests

• Ceruloplasmin
• Urine succinylacetone
• Plasma amino acids
• Urine organic acids

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Imaging

Ultrasound Abdomen with Doppler

Useful for:

• Liver size
• Vascular patency
• Ascites
• Chronic liver disease exclusion

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Important ICU Monitoring

Continuous monitoring of:

• Mental status
• Blood glucose
• ICP signs
• Urine output
• Electrolytes
• INR
• Ammonia

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Management of Acute Hepatic Failure

Core Principles

• PICU admission
• Aggressive supportive care
• Prevent cerebral edema
• Treat underlying cause
• Early transplant referral

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Stabilization

Airway

Intubate if:

• Grade III/IV encephalopathy
• Airway compromise

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Circulation

Maintain:

• Adequate perfusion
• MAP
• Renal function

Avoid fluid overload.

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Management of Hypoglycemia

Frequent glucose monitoring is mandatory.

Treatment:

• Dextrose bolus
• Continuous glucose infusion

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Cerebral Edema Management

General Measures

• Head elevation to 30°
• Avoid neck compression
• Minimize stimulation

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Osmotherapy

Mannitol

• 0.5–1 g/kg IV

OR

Hypertonic Saline

Target serum sodium:

• 145–150 mEq/L

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Ammonia Reduction

Lactulose

Reduces ammonia absorption from gut.

Renal Replacement Therapy

Indicated for:

• Severe hyperammonemia
• Renal failure

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Coagulopathy Management

Important principle:

• Do NOT correct INR routinely unless bleeding or procedure planned.

Options

• Vitamin K
• FFP
• Cryoprecipitate
• Platelets

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Infection Control

High suspicion for:

• Bacterial infections
• Fungal sepsis

Empiric antibiotics are often used in critically ill patients.

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Etiology-Specific Treatment

Acetaminophen Toxicity

N-acetylcysteine (NAC)

Acts by:

• Replenishing glutathione
• Improving hepatic perfusion

$\text{N-acetylcysteine restores glutathione and reduces } NAPQI \text{ toxicity}$N-acetylcysteine restores glutathione and reduces NAPQI toxicity

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HSV Hepatitis

• IV acyclovir

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Autoimmune Hepatitis

• Corticosteroids

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Wilson Disease

Usually requires urgent liver transplantation.

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Nutrition in Acute Hepatic Failure

Key Principles

• Early enteral nutrition preferred
• Avoid prolonged fasting
• Adequate calories essential

Protein

Previously restricted heavily, but modern pediatric guidelines recommend:

• Avoid excessive restriction
• Individualize according to encephalopathy severity

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Liver Transplantation in Acute Hepatic Failure

Indications

• Progressive encephalopathy
• Refractory coagulopathy
• Severe acidosis
• Persistent hyperammonemia
• Multi-organ failure

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Poor Prognostic Factors

• INR worsening
• Severe encephalopathy
• Cerebral edema
• Renal failure
• Rising bilirubin
• Persistent lactic acidosis

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Complications of Acute Hepatic Failure

Neurologic

• Cerebral edema
• Seizures
• Herniation

Hematologic

• Bleeding
• DIC

Renal

• Hepatorenal syndrome
• AKI

Infectious

• Sepsis
• Fungal infections

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Prognosis

Outcome depends on:

• Etiology
• Speed of recognition
• Availability of transplant
• Degree of encephalopathy

Better Prognosis

• Hepatitis A
• Acetaminophen toxicity (early NAC)

Worse Prognosis

• Wilson disease
• Indeterminate PALF
• Severe cerebral edema

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High-Yield Exam Points on Acute Hepatic Failure

Most Important Diagnostic Marker

• Elevated INR

Most Common Cause in Developed Countries

• Acetaminophen toxicity

Major Cause of Death

• Cerebral edema and sepsis

Drug of Choice in Acetaminophen Toxicity

• N-acetylcysteine

Key Emergency

• Raised intracranial pressure

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Acute Hepatic Failure Flowchart

Acute Liver Injury
        ↓
Coagulopathy (INR ↑)
        ↓
Evaluate Etiology
        ↓
PICU Supportive Care
        ↓
Prevent Cerebral Edema
        ↓
Treat Specific Cause
        ↓
Assess for Liver Transplant

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Frequently Asked Questions (FAQs)

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Key Takeaway

Acute hepatic failure in children is a rapidly progressive and potentially fatal condition requiring:

• Early diagnosis
• Intensive monitoring
• Prevention of cerebral edema
• Etiology-directed therapy
• Timely liver transplantation evaluation

Rapid recognition and evidence-based critical care significantly improve survival outcomes.