Hyperreflexia

Definition

Liver encephalopathy is a potentially life-threatening disease in which toxic substances accumulate in the blood. Also known as hepatic encephalopathy or hepatic coma, this condition can cause confusion, disorientation, abnormal neurological signs, loss of consciousness, and death.

Description

A normally functioning liver metabolizes and detoxifies substances formed in the body during the digestive process. Impaired liver function allows substances like ammonia (formed when the body digests protein), some fatty acids, phenol, and mercaptans to escape into the bloodstream. From there, they may penetrate the blood-brain barrier, affect the central nervous system (CNS), and lead to hepatic coma.

Hepatic coma is most common in patients with chronic liver disease. It occurs in 50-70% of all those with cirrhosis.

Causes & symptoms

The cause of hepatic coma is unknown, but the condition is frequently associated with the following conditions:

• Acute or chronic liver disease
• Gastrointestinal bleeding
• Azotemia, the accumulation of nitrogen-containing compounds (such as urea) in the blood
• Inherited disorders that disrupt the process by which nitrogen is decomposed and excreted
• The use of shunts (devices implanted in the body to redirect the flow of fluid from one vessel to another)
• Electrolyte imbalances, including low levels of potassium (hypokalemia) and abnormally alkaline blood pH (alkalosis). These imbalances may result from the overuse of sedatives, analgesics, or diuretics; reduced levels of oxygen (hypoxia), or withdrawal of excessive amounts of body fluid (hypovolemia)
• Constipation, which may increase the body's nitrogen load
• Surgery
• Infection
• Acute liver disease.

Binge drinking and acute infection are common causes of hepatic coma in patients with long-standing liver disease.

Symptoms of hepatic encephalopathy range from almost unnoticeable changes in personality, energy levels, and thinking patterns to deep coma.

Inability to reproduce a star or other simple design (apraxia) and deterioration of handwriting are common symptoms of early encephalopathy. Decreased brain function can also cause inappropriate behavior, lack of interest in personal grooming, mood swings, and uncharacteristically poor judgment.

The patient may be less alert than usual and develop new sleep patterns. Movement and speech may be slow and labored.

As the disease progresses, patients become confused, drowsy, and disoriented. The breath and urine acquires a sweet, musky odor. The hands shake, the outstretched arms flap (asterixis or "liver flap"), and the patient may lapse into unconsciousness. As coma deepens, reflexes may be heightened (hyperreflexia). The toes sometimes splay when the sole of the foot is stroked (Babinski reflex).

Agitation occasionally occurs in children and in adults who suddenly develop severe symptoms. Seizures are uncommon.

Diagnosis

The absence of sensitive, reliable tests for encephalopathy make the physician's personal observations and professional judgment the most valuable diagnostic tools.

Confusion, disorientation, and other indications of impaired brain function strongly suggest encephalopathy in patients known to have liver disease. CAT scans and examination of spinal fluid don't provide diagnostic clues. Elevated arterial ammonia levels are almost always present in hepatic coma, but levels are not necessarily correlated with the severity or extent of the disease.

Magnetic resonance imaging (MRI) can show severe brain swelling that often occurs prior to coma, and electroencephalography (EEG) detects abnormal brain waves even in patients with early, mild symptoms. Blood and urine analyses can provide important information about the cause of encephalopathy in patients suspected of taking large quantities of sedatives or other drugs.

Treatment

This condition may disappear if the cause of symptoms is eliminated. In other cases, treatment is designed to improve liver function as much as possible; remove or relieve factors that worsen symptoms; and decrease the body's production of poisonous substances.

All non-essential medications are discontinued. Soft restraints are recommended in place of sedatives for patients who become agitated.

Enemas or laxatives are used to stimulate expulsion of toxic intestinal products. All or most protein is eliminated from the diet, and supplemental feeding may be necessary to replenish lost calories. Regular doses of neomycin (Neobiotic), taken orally or administered to comatose patients in liquid form through a tube, may be used to decrease production of protein-digesting bacteria in the bowel.

Lactulose, a synthetic sugar, changes the characteristics of intestinal bacteria, decreases the amount of ammonia accumulated in the body, and has laxative properties. The patient is given hourly doses of lactulose syrup until diarrhea occurs, then dosage is adjusted to maintain regular bowel function. Lactulose and dietary-protein restrictions may be used to control chronic encephalopathy.

Prognosis

Encephalopathy may be reversible if the responsible factor is identified and removed or treated. Patients whose condition is the result of chronic liver disease may recover completely after the underlying cause is corrected.

Despite intensive treatment, encephalopathy caused by acute liver inflammation (fulminant hepatitis) is fatal for as many as 80% of patients. Those with chronic liver failure often die in hepatic coma.

Key Terms

Cirrhosis

A serious disease of the liver caused by chronic damage to its cells and the eventual formation of scar tissue (fibrosis).

Coma

A condition of deep unconsciousness from which the person cannot be aroused

Electrolytes

Substances that conduct electricity when they are in solution. In the body, electrolytes in the blood and tissues enable nerve impulses to flow normally.

Encephalopathy

A dysfunction of the brain. Hepatic encephalopathy is brain dysfunction that occurs because the liver isn't removing harmful substances from the blood.

Further Reading

For Your Information

Books

• Bennet, J. Claude, and Fred Plum, eds. Cecil Textbook of Medicine. Philadelphia, PA: W.B. Saunders Co., 1996.
• Berkow, Robert, ed. The Merck Manual of Medical Information: Home Edition. Whitehouse Station, NJ: Merck & Co., Inc., 1997.
• Isselbacher, Kurt, J., et al., eds. Harrison's Principles of Internal Medicine. New York, NY: McGraw-Hill, Inc., 1994.

  Organizations

• American Liver Foundation. 1425 Pompton Avenue, Cedar Grove, NJ 07009. (800) GO-LIVER. http://www.liverfoundation.org/.

  Other

• Hepatic and Biliary Disorders. http://www.merck.com/!!tKNH50WVitKNRZ2qCQ/pubs/mmanual/html/hkfeqk.htm (12 May 1998).
• Treatment of Hepatic Encephalopathy. http://www.ginet.com/papers/mpape.324.htm (12 May 1998).

Gale Encyclopedia of Medicine. Gale Research, 1999.