hepatic encephalopathy

Hepatic encephalopathy (also known as portosystemic encephalopathy) is the occurrence of confusion, altered level of consciousness and coma as a result of liver failure. In the advanced stages it is called hepatic coma or coma hepaticum. It may ultimately lead to death.[1]

It is caused by accumulation in the bloodstream of toxic substances that are normally removed by the liver. The diagnosis of hepatic encephalopathy requires the presence of impaired liver function and the exclusion of an alternative explanation for the symptoms. Blood tests (ammonia levels) may assist in the diagnosis. Attacks are often precipitated by an intercurrent problem, such as infection or constipation.[1][2]

Hepatic encephalopathy is reversible with treatment. This relies on suppressing the production of the toxic substances in the intestine and is most commonly done with the laxative lactulose or with non-absorbable antibiotics. In addition, the treatment of any underlying condition may improve the symptoms. In particular settings, such as acute liver failure, the onset of encephalopathy may indicate the need for a liver transplan

Signs and symptoms

The mildest form of hepatic encephalopathy is difficult to detect clinically, but may be demonstrated on neuropsychological testing. It is experienced as forgetfulness, mild confusion and irritability. More severe encephalopathy is characterised by an inverted sleep-wake pattern (sleeping by day, being awake at night), marked irritability, tremor, difficulties with coordination and trouble writing.[1]

More severe forms of hepatic encephalopathy lead to a worsening level of consciousness, from lethargy to somnolence and eventually coma. In the intermediate stages, a characteristic jerking movement of the limbs is observed (asterixis, "liver flap" due to its flapping character); this disappears as the somnolence worsens. There is disorientation and amnesia, and uninhibited behaviour may occur. Coma and seizures represent the most advanced stage; cerebral oedema (swelling of the brain tissue) leads to death.[1]

Encephalopathy often occurs together with other symptoms and signs of liver failure. These may include jaundice (yellow discolouration of the skin and the whites of the eyes), ascites (fluid accumulation in the abdominal cavity), and peripheral oedema (swelling of the legs due to fluid build-up in the skin). The tendon reflexes may be exaggerated, and the plantar reflex may be abnormal, namely extending rather than flexing (Babinski's sign) in severe encephalopathy. A particular smell (foetor hepaticus) may be detected

Causes

In a small proportion of cases, the encephalopathy is caused directly by liver failure; this is more likely in acute liver failure. More commonly, especially in chronic liver disease, hepatic encephalopathy is caused or aggravated by an additional cause, and identifying these causes can be important to treat the episode effectively.[1]Type Causes[1][2][4]
Excessive
nitrogen load Consumption of large amounts of protein, gastrointestinal bleeding e.g. from esophageal varices (blood is high in protein, which is reabsorbed from the bowel), renal failure (inability to excrete nitrogen-containing waste products such as urea), constipation
Electrolyte or
metabolic disturbance Hyponatraemia (low sodium level in the blood) and hypokalaemia (low potassium levels)—these are both common in those taking diuretics, often used for the treatment of ascites; furthermore alkalosis (decreased acid level), hypoxia (insufficient oxygen levels), dehydration
Drugs and
medications Sedatives such as benzodiazepines (often used to suppress alcohol withdrawal or anxiety disorder), narcotics (used as painkillers or drugs of abuse) and sedative antipsychotics, alcohol intoxication
Infection Pneumonia, urinary tract infection, spontaneous bacterial peritonitis, other infections
Others Surgery, progression of the liver disease, additional cause for liver damage (e.g. alcoholic hepatitis, hepatitis A)
Unknown In 20–30% of cases, no clear cause for an attack can be found

Hepatic encephalopathy may also occur after the creation of a transjugular intrahepatic portosystemic shunt (TIPSS). This is used in the treatment of refractory ascites, bleeding from oesophageal varices and hepatorenal syndrome.[5][6] TIPSS-related encephalopathy occurs in about 30% of cases, with the risk being higher in those with previous episodes of encephalopathy, higher age, female sex and liver disease due to causes other than alcohol

Classification and grading
[West Haven Criteria

The severity of hepatic encephalopathy is graded with the West Haven Criteria; this is based on the level of impairment of autonomy, changes in consciousness, intellectual function, behavior, and the dependence on therapy.[1][7][8]
Grade 1 - Trivial lack of awareness; euphoria or anxiety; shortened attention span; impaired performance of addition or subtraction
Grade 2 - Lethargy or apathy; minimal disorientation for time or place; subtle personality change; inappropriate behaviour
Grade 3 - Somnolence to semistupor, but responsive to verbal stimuli; confusion; gross disorientation
Grade 4 - Coma (unresponsive to verbal or noxious stimuli

.Investigations

The diagnosis of hepatic encephalopathy can only be made in the presence of confirmed liver disease (types A and C) or a portosystemic shunt (type B), as it leads to similar symptoms to other encephalopathies. To make the distinction, abnormal liver function tests and/or ultrasound suggesting liver disease are required, and ideally liver biopsy.[1][2] The symptoms of hepatic encephalopathy may also arise from other conditions, such as cerebral haemorrhage and seizures (both of which are more common in chronic liver disease). A CT scan of the brain may be required to exclude haemorrhage, and if seizure activity is suspected an electroencephalograph (EEG) study may be performed.[1] Rarer mimics of encephalopathy are meningitis, encephalitis, Wernicke's encephalopathy and Wilson's disease; these may be suspected on clinical grounds and confirmed with investigations.[2][7]

The diagnosis of hepatic encephalopathy is a clinical one, once other causes for confusion or coma have been excluded; no test fully diagnoses or excludes it. Serum ammonia levels are elevated in 90% of patients, but not all hyperammoninaemia (high ammonia levels) is associated with encephalopathy.[1][2] A CT scan of the brain usually shows no abnormality except in stage IV encephalopathy, when cerebral oedema may be visible.[2] Other neuroimaging modalities, such as magnetic resonance imaging (MRI), are not currently regarded as useful, although they may show abnormalities.[7] Electroencephalography shows no clear abnormalities in stage 0, even if minimal HE is present; in stages I, II and III there are triphasic waves over the frontal lobes that oscillate at 5 Hz, and in stage IV there is slow delta wave activity.[1] However, the changes in EEG are not typical enough to be useful in distinguishing hepatic encephalopathy from other conditions.[7]

Once the diagnosis of encephalopathy has been made, efforts are made to exclude underlying causes (such as listed above in "causes"). This requires blood tests (urea and electrolytes, full blood count, liver function tests), usually a chest X-ray, and urinalysis. If there is ascites, diagnostic paracentesis (removal of a fluid sample with a needle) may be required to identify

spontaneous bacterial peritonitis

Treatment

Those with severe encephalopathy (stages 3 and 4) are at risk of obstructing their airway due to decreased protective reflexes such as the gag reflex. This can lead to respiratory arrest. Transferring the patient to a higher level of nursing care, such as an intensive care unit, is required and intubation of the airway is often necessary to prevent life-threatening complications (e.g., aspiration or respiratory failure).[2][3] Placement of a nasogastric tube permits the safe administration of nutrients and medication.[1]

The treatment of hepatic encephalopathy depends on the suspected underlying cause (types A, B or C) and the presence or absence of underlying causes. If encephalopathy develops in acute liver failure (type A), even in a mild form (grade 1–2), it indicates that a liver transplant may be required, and transfer to a specialist centre is advised.[3] Hepatic encephalopathy type B may arise in those who have undergone a TIPSS procedure; in most cases this resolves spontaneously or with the medical treatments discussed below, but in a small proportion of about 5%, occlusion of the shunt is required to address the symptoms.[4]

In hepatic encephalopathy type C, the identification and treatment of alternative or underlying causes is central to the initial management.[1][2][4][10] Given the frequency of infection as the underlying cause, antibiotics are often administered empirically (without knowledge of the exact source and nature of the infection).[1][4] Once an episode of encephalopathy has been effectively treated, a decision may need to be made on whether to prepare for a liver transplant

thanks gawhara

important topic

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