Hepatic Encephalopathy

Hepatic Encephalopathy is a topic covered in the 5-Minute Emergency Consult.

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Basics

Description

Hepatic encephalopathy (HE) is characterized by changes in behavior, consciousness, and motor disturbances, associated with hepatic insufficiency and the accumulation of substances normally metabolized by the liver. HE may result from a combination of:
  • Accumulation of ammonia (NH3) from:
    • Protein degradation by colonic bacteria
    • Deamination of glutamine in small bowel, kidney, and muscle.
    • Accumulated NH3 crosses the blood–brain barrier. Astrocytes uptake NH3 and metabolize it into glutamine which causes cellular swelling. Ultimately leads to cerebral edema and cerebral mitochondrial dysfunction.
  • Accumulation of other neurotoxins:
    • Short-chain fatty acids
    • Manganese toxicity
    • Neurosteroids
    • Phenols
    • Mercaptans
    • Amino acids such as tryptophan
  • Increased levels of inhibitory neurotransmitters:
    • Benzodiazepines
    • γ-aminobutyric acid (GABA)
    • Serotonin
  • Decreased levels of excitatory neurotransmitters:
    • Glutamate
    • Dopamine
    • Aspartate
    • Catecholamines
  • Other contributing factors to HE:
    • Decreased cerebral blood flow and oxygen
    • Increased glucose consumption and possible hypoglycemia
    • Zinc deficiency
  • Genetics:
    • Inherited errors of the urea cycle

Etiology

  • Classification based on the 11th World Congress of Gastroenterology:
    • Type A: HE associated with acute liver injury and fulminant hepatic failure (FHF).
    • Type B: HE associated with portosystemic bypass and no intrinsic liver disease.
    • Type C: HE associated with cirrhosis and portal hypertension.
  • Precipitating events:
    • GI bleeding (more common in elderly)
    • Hypokalemia and hyponatremia.
    • Alkalosis decreases renal NH4 excretion.
    • Sepsis (e.g., spontaneous bacterial peritonitis [SBP])
    • Constipation
    • Noncompliance with treatment regimen in chronic liver failure
    • High-protein diet
    • Hypoglycemia
    • Hypovolemia (e.g., post large-volume paracentesis)
    • Azotemia (e.g., diuretic or diarrhea induced)
    • Narcotics or sedatives, including alcohol
    • Zinc deficiency as multiple urea cycle enzymes are zinc dependent
    • Hepatocellular injury
    • Viral- or drug-induced hepatitis
    • Post portosystemic shunt placement
    • Recurrent encephalopathy can occur without precipitating factors

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Citation

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TY - ELEC T1 - Hepatic Encephalopathy ID - 307623 Y1 - 2016 PB - 5-Minute Emergency Consult UR - https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307623/all/Hepatic_Encephalopathy ER -