Ammonia Lab Value

One of the lab values that is commonly ordered on patients in the hospital is an ammonia level. Ammonia is a natural waste product of the human body. It is nitrogen-based compound resulting from the digestion of protein in the intestines by bacteria. If it is not processed and excreted properly, levels can increase and cross the blood brain barrier (which is toxic to the brain).

Symptoms

In infants, an elevated ammonia level manifests itself with symptoms such as vomiting, irritability, lethargy, and even seizures. As adults, symptoms manifest themselves as disorientation, change in level of consciousness, sleepiness, and lethargy. Any of these symptoms are indications for the provider to order an ammonia level to determine if this may be the cause.

Ammonia Elevation in Infants

Causes: "In infants, an extremely high level is associated with an inherited urea cycle enzyme deficiency or defect but may also be seen with hemolytic disease of the newborn. Moderate short-lived increases in ammonia are relatively common in newborns, where the level may rise and fall without causing noticeable symptoms." -Lab Tests Online

Treatment: When there is an Rh incompatability suspected (which causes hemolytic disease of the newborn), Rh immune-globulin injections are administered to the mother to prevent her body from producing antibodies against the developing fetus.

Ammonia Elevation in Children

Causes: The main cause of ammonia elevation in children is from Reye's Syndrome. With this condition, children develop a low blood sugar and high ammonia and acidity levels in their blood. There may be swelling in both the liver and the brain. Symptoms usually develop 3-5 days after onset of a viral infection such as chicken pox or influenza. This has been linked to children receiving aspirin in conjunction with the viral infection.

Treatment: There is no known treatment for Reye's Syndrome, only symptom management. Severe cases may require the use of diuretics to decrease intracranial swelling, IV fluids with dextrose and/or electrolytes, and medications to prevent bleeding.

Ammonia Elevation in Adults

Causes: There are two common causes of ammonia elevation in adults:

Liver Failure: The liver normally converts ammonia into urea, which is then excreted in the urine. If the liver is not functioning properly, this process does not take place and ammonia levels rise. Cirrhosis has been the most common reason I have seen for elevated ammonia levels.
Kidney Failure: When the kidneys are not functioning properly, waste products (such as ammonia and urea) are not excreted into the urine and removed from the body.

Treatment: The most common treatment used to decrease ammonia levels in adults is a laxative called lactulose. This can be given both orally and as an enema. This decreases the absorption of ammonia in the digestive tract and causes the body to excrete an increased level of ammonia.