Fulminant Hepatic Failure((acute liver failure)
DEFINITION
Is a clinical syndrome resulting from massive necrosis of hepatocytes or from severe functional impairment of hepatocytes.
Synthetic, excretory, and detoxifying
functions of the liver are all severely impaired.
This narrow definition may be problematic
because early hepatic encephalopathy
can be difficult to detect in infants and children.
The currently accepted definition in children includes
biochemical evidence of acute liver
injury (usually <8 wk duration);
no evidence of chronic liver disease
hepatic-based coagulopathy defined as a prothrombin time (PT)
15 sec or international normalized ratio (INR) >1.5 not corrected by
vitamin K in the presence of clinical hepatic encephalopathy,
or a PT >20 sec or INR >2 regardless of the presence of clinical hepatic encephalopathy.
Liver failure in the perinatal period can be associated with
prenatal liver injury and even cirrhosis. Examples include neonatal
iron storage (hemochromatosis) disease, tyrosinemia, and some cases
of congenital viral infection.
Liver disease may be noticed at birth or after several days of apparent well-being.
In some cases of liver disease failure, particularly in the idiopathic form of acute hepatic failure, the
onset of encephalopathy occurs later, from 8-28 wk after the onset of
jaundice.
ETIOLOGY
Fulminant hepatic failure can be a complication of viral hepatitis (A,
B, D, E).
An unusually high risk in combined infections with hepatitis B virus (HBV) and hepatitis D.
Mutation in procore and promoter region of HBV DNA.
Hepatitides C and E viruses are uncommon causes of fulminant hepatic failure
Patients with chronic hepatitis C are at risk if they have superinfection with hepatitis A virus.
Epstein-Barr virus, herpes simplex virus, adenovirus, enteroviruses,
cytomegalovirus, parvovirus B19, human herpesvirus-6, and varicellazoster infections
autoimmune hepatitis in approximately 5% of cases.
common features of hemophagocytic lymphohistocytosis
organ transplantation and malignancies.
An idiopathic form of fulminant hepatic failure accounts for 40-50% of cases in children.
Various hepatotoxic drugs and chemical
After exposure to carbon tetrachloride or Amanita phalloides mushrom
Acetaminophen over dose is the most common etiology of acute hepatic failure in children and adolescents
Idiosyncratic damage can follow the use of drugs such as halothane, isoniazid, or sodium valproate and herbal supplements
Ischemia and hypoxia resulting from hepatic vascular occlusion, severe heart failure, cyanotic congenital heart disease, or circulatory shock can produce liver failure.
Metabolic disorders associated with
hepatic failure include Wilson disease, galactosemia, hereditary tyrosinemia, fructose intolerance, neonatal iron storage disease, defects in ฮฒ-oxidation of fatty acids, and deficiencies of mitochondrial electron transport.
CLINICAL MANIFESTATIONS
Fulminant hepatic failure can be the presenting feature of liver disease or it can complicate previously known liver disease (acute-on-chronic liver failure).
A history of developmental delay and/or neuromuscular dysfunction can indicate an underlying mitochondrial or ฮฒ-oxidation
defect.
A child with fulminant hepatic failure has usually been previously healthy and most often has no risk factors for liver disease such
as exposure to toxins or blood products. Progressive jaundice, fetor hepaticus, fever, anorexia, vomiting, and abdominal pain are common.
A rapid decrease in liver size without clinical improvement is an ominous sign.
A hemorrhagic diathesis and ascites can develop.
Patients should be closely observed for hepatic encephalopathy, which is initially characterized by minor disturbances of consciousness or motor function.
Irritability, poor feeding, and a change in sleep rhythm may be the only findings in infants
Asterixis may be demonstrable in older children.
Patients are often somnolent, confused, or
combative on arousal and can eventually become responsive only to painful stimuli.
Patients can rapidly progress to deeper stages of coma in which extensor responses and decerebrate and decorticate posturing
appear.
Respirations are usually increased early, but respiratory failure can occur in stage IV coma