Hepatic Encephalopathy

Definition And Classification

Metabolically induced, potentially reversible functional disturbance of brain.
Principal manifestation of acute liver failure and chronic liver disease.
Type A: Occurs in acute liver failure.
Type B: Occurs in portosystemic shunting without intrinsic hepatocellular disease.
Type C: Occurs in chronic liver disease.
Subclassifications of Type C: Minimal, episodic, or persistent.
Minimal Hepatic Encephalopathy (Covert HE): Subclinical manifestation detectable exclusively via psychometric tests or electrophysiological techniques. Compromises attention, processing speed, and psychomotor performance.

Ammonia produced primarily in large intestine via bacterial protein breakdown, muscle, and kidney.
Healthy liver converts ammonia to urea or glutamine.
Failing liver permits systemic ammonia accumulation; ammonia crosses blood-brain barrier.
Glial cells convert excess ammonia to glutamine.
Intracellular glutamine accumulation increases osmotic pressure.
Results in astrocyte swelling and profound cerebral edema.
Glutamine competitively inhibits glutamate receptors.
Induces oxidative stress triggering mitochondrial dysfunction.

Decreased Fischer ratio (branched-chain amino acids to aromatic amino acids).
Aromatic amino acids (phenylalanine, tyrosine, tryptophan) cross blood-brain barrier.
Promotes synthesis of false neurotransmitters (octopamine, synephrine).
Short-chain fatty acids (propionate, butyrate) competitively inhibit urea cycle enzymes.
Elevated gamma-aminobutyric acid, serotonin, and endogenous benzodiazepine-like compounds alter neurotransmission.

Minor disturbances of consciousness or motor function initially.
Infants exhibit irritability, poor feeding, inverted sleep rhythm.
Older children exhibit asterixis (flapping tremor), hypertonia, and hyperreflexia.
Progression yields hypotonia, areflexia, and coma.
Parkinsonian features (muscular rigidity, bradykinesia, hypokinesia, monotony of speech, resting tremors) possible.

Grade	Clinical Signs	Neurologic/Reflex Findings	Electroencephalogram Changes
0	Normal behavior.	Normal.	Normal alpha rhythm.
1	Euphoria/anxiety, shortened attention span, trivial lack of awareness, inverted sleep pattern.	Normal or hyperreflexia.	Appearance of theta rhythm.
2	Subtle personality change, minimal time/place disorientation, lethargy, inappropriate behavior.	Tremor, apraxia, dysarthria, ataxia, hyperreflexia.	Continuous theta rhythm, occasional delta waves.
3	Somnolence to semi-stupor, gross disorientation, combativeness, confusion.	Brisk reflexes, Babinski sign, muscle rigidity.	Prevalent theta rhythm, polyphasic spikes.
4	Deep coma (unresponsive to verbal or noxious stimuli).	Absent reflexes, decerebrate/decorticate posturing.	Continuous delta waves.

Diagnosis relies primarily on clinical history and examination.
Utilize Wechsler intelligence tests or Dutch child intelligence test for neuropsychological assessment.
Psychometric hepatic encephalopathy score lacks validation in children.

Critical Flicker Frequency: Quantifies low-grade encephalopathy in children >8 years. Patients perceive flicker only below 39 Hz threshold.
Electroencephalogram: Grades severity (0-4) based on background rhythm slowing and presence of delta/theta waves.
Neuroimaging: Computed tomography excludes organic causes (intracranial hemorrhage, tumors). Magnetic resonance imaging detects cerebral edema and demyelination. Proton magnetic resonance spectroscopy measures elevated brain glutamine and depleted myo-inositol/choline.

Stabilize patient; actively identify and reverse precipitating factors.
Elective intubation indicated for grade 3 or 4 encephalopathy for airway protection and facilitating hyperventilation.
Optimize intravascular hydration; monitor central venous pressure (target 6-8 cm H2O).
Avoid rapid fluid boluses; exacerbates cerebral edema.
Avoid sedatives; prefer opiates over benzodiazepines if sedation mandated for mechanical ventilation.

Maintain adequate caloric intake.
Restrict protein (1 g/kg) only initially (first 24-48 hours) or in intractable encephalopathy.
Prolonged protein restriction contraindicated; worsens catabolism and depletes muscle mass.
Muscle acts as critical ammonia buffer; muscle loss exacerbates hyperammonemia.
Prefer plant protein and branched-chain amino acids over animal protein and aromatic amino acids.

Lactulose: Decreases colonic pH to ~5, reducing bacterial fermentation. Converts ammonia to non-diffusible ammonium ion for fecal excretion. Titrate dosage to achieve three soft stools daily.
Lactitol: Non-absorbable sugar alternative; more palatable than lactulose.
Antibiotics: Rifaximin offers safe oral bowel decontamination; superior safety profile compared to neomycin (neomycin associated with nephrotoxicity and ototoxicity).
L-ornithine-L-aspartate: Enhances transaminase activity converting ammonia to non-toxic glutamate. Maximum infusion rate 5 g/h (up to 20 g/day); not recommended for children <8 years.
Ammonia Scavengers: Sodium benzoate and sodium phenylacetate eliminate ammonia via alternate pathways (excreted renally as hippuric acid and phenylacetyl-glutamine).

Administer mannitol (0.5 g/kg 20% solution bolus over 15 minutes). Repeat if serum osmolarity <320 mOsm/L.
Induce mild cerebral hypothermia (32-35°C).
Maintain hypernatremia (serum sodium >145 mmol/L) to prevent fluid shifts.
Maintain cerebral perfusion pressure >50 mm Hg utilizing inotropic agents (noradrenaline preferred).
Consider continuous kidney replacement therapy for hyperammonemia >150-200 µmol/L with grade III-IV encephalopathy.

Liver transplantation remains sole definitive treatment for reversing chronic hepatic encephalopathy and end-stage liver disease.