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Hepatic encephalopathy

From Mediwikis


Hepatic encephalopathy (HE) is one of the main complications of hepatic (liver) cirrhosis, mainly characterized by neurological changes.

It can be either acute or chronic, depending on the underlying presentation.

  • Acute if 2º to acute hepatic failure
  • Chronic if 2º to portal hypertension (2º to hepatic cirrhosis)

Acronym for precipitating factors of HE = HEPATICS

H = Haemorrhage / Hyperkalaemia

E = Excess dietary protein

P = Paracentesis

A = Acidosis / Anaemia

T = Trauma

I = Infection (e.g SBP, another complication of cirrhosis)

C = Colon surgery

S = Sedatives (e.g opiates, benzodiazepines)

Pathophysiology (Ammonia theory)

Ammonia is naturally produced in the gut as a result of bacterial metabolism of protein. This is then absorbed through the gut wall and enters the portal venous system where it is carried to the liver for detoxification.

However, in cirrhosis the collateral circulation opens up which produces a shunt across the liver. Ammonia is therefore carried directly into the brain (without detox) where it exerts its neurotoxic effects.

Astrocyte swelling occurs as a result of detoxification of glutamate into glutamine (via ammonia) which increases intracellular osmolarity. In addition, ammonia reduces cerebral ATP levels and agonizes GABA function (an inhibitory neurotransmitter).

Clinical features

Chronological changes

  • Personality disorders → Mood → Higher functioning → Sleep disturbance → Drowsiness → Confusion → Comatose

4 signs of HE

  • Hepatic flap (a.k.a asterixis)
  • Fetor hepaticus (sweat smell in breath)
  • Confusion
  • Constructional apraxia (inability to draw a 5-pointed star)

Diagnosis & Investigations

Purely clinical, though other investigations may help with diagnostic uncertainty. Search for precipitating factors (HEPATICS).

West-Haven criteria for HE

Grade 1 = mild impairment

Grade 2 = moderate impairment

  • Disorientation, lethargy, personality disorders, hepatic flap, ataxia, hypoactive reflexes

Grade 3 = severe impairment

  • Confusion, somnolence, clonus, hyperactive reflexes, Babinski's reflex

Grade 4 = coma

Investigations (additional)

  • LFTs
  • EEG
  • Visual evoked responses
  • Arterial / Serum ammonia & MRI / CT scans for DDx

Differential Diagnoses (DDx)

  • Hypoglycaemia
  • Post-seizure
  • Sepsis / Infections
  • Head trauma (a.k.a subdural haematoma)
  • Wilson's disease
  • Beriberi syndrome
  • Urea cycle disorders

Management

Protect the brain via removing nitrogenous load (ammonia)

  • 1º = lactulose ± phosphate enema
  • 2º = lactulose + rifaximin / L-ornithine L-aspartate (LOLA)
  • 3º = lactulose + rifaximin + LOLA

Important points

  • Remove precipitating factors
  • Maintain proper nutrition & DON'T restrict protein

Prognosis

Potentially reversible with variable prognosis.

Acute presentations have poor prognosis.