Introduction
Hyperammonemia is a term used to describe the high levels of ammonia in the body. Ammonia, also known as NH3, is a waste product that is produced by the intestines when the body digests protein. After this, the liver processes ammonia, which is then excreted through urine. The normal level of ammonia depends on the age of an individual. Although the normal level of ammonia in a healthy infant may vary in different laboratories, 50 to 150 μg/dl (micrograms per deciliter), but values above 75 μg/dl in newborns and levels above 150 μg/dl are considered abnormal. One such condition when the level of ammonia elevates in preterm newborns is known as transient hyperammonemia of the newborn.
What Is Transient Hyperammonemia of The Newborn?
Transient hyperammonemia of newborns is a life-threatening condition occurring in newborns in which the ammonia level is more than normal. This condition may occur due to factors like an inherited metabolic disease. In addition, high ammonia levels may affect the normal urea cycle in newborns.
What Causes Transient Hyperammonemia of The Newborn?
A genetic disorder is thought to be the primary cause of transient hyperammonemia in newborns. Still, it has yet to be narrowed down to one gene, so the exact reason remains unclear. Some of the additional causes of hyperammonemia in newborns include:
Liver Failure - It is a condition in which the liver does not function properly, such as producing bile, digesting food, and clearing toxins like ammonia from the body. In newborns, the ammonia level increases in the body when the liver is impaired. Liver failure can be of two types, acute and chronic. Acute liver failure is the loss of liver function over the days or weeks after a child is born. Acute liver failure can occur for several reasons, such as viral infections and drug-induced liver injury.
Urea Cycle Disorder (UCD) - It is an inborn error of metabolism that can lead to a high ammonia level in newborns. UCD is seen to affect around 23 percent of hyperammonemia cases in newborns. Several types of UCD are identified by the lack of certain enzymes and proteins, and one such affecting newborns are ornithine transcarbamylase deficiency (OTC). OTC is an X-linked disorder and is usually more severe for male newborns.
What Are the Symptoms of Transient Hyperammonemia of The Newborn?
The symptoms of transient hyperammonemia in the newborn can be observed within the first two to three days after the child is born. Some of the symptoms include:
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Lethargy - It is a term for little or no energy seen in infants. The infant may sleep for more hours than usual and be drowsy.
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Poor Feeding - The newborn may show signs like a lack of interest in feeding due to metabolic or neurological disorders.
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Reye’s Syndrome - It is a rare disorder that causes swelling in the brain and liver. In infants with liver failure, this is one of the major symptoms. Emergency care is required for symptoms like confusion, seizures, and loss of consciousness. Reye's syndrome can be diagnosed and treated early enough to save a child's life.
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Respiratory Distress Syndrome - It occurs when fluids accumulate in the lungs' air sacs. It may cause shortness of breath and low blood pressure. This is diagnosed by taking chest X-rays and blood tests.
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Seizures - It is a sudden uncontrolled disturbance in the brain. It is one of the most common symptoms of transient hyperammonemia in newborns.
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Metabolic Acidosis - It is a build-up of acid in the body. It may cause nausea, vomiting, and abdominal pain.
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Cyanosis - It is the change in body tissue to bluish-purple due to low oxygen levels in the blood.
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Hypothermia - It is a term given for lower body temperature than normal. It may show symptoms like shivering, weak pulse, and drowsiness.
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Hypotonia - It is a medical term used for decreased muscle tone. The infant will have a floppy or saggy muscle when held. This is one of the reasons infants have trouble feeding.
How Is Transient Hyperammonemia of The Newborn Diagnosed?
Depending upon the symptoms, a number of tests can be advised.
Newborn screening blood test, plasma lactic acid test (in case of metabolic acidosis), liver function test, and amino acid blood test are some of the blood tests to check the level of each mentioned in the blood.
Most of these blood tests take the blood sample from the infant’s foot heel. First, a healthcare expert will use a fine needle to prick the infant's heel. Next, a little pressure is given on the heel to draw out the blood, which is collected in a sterile container. The infant may feel slight pain and discomfort. The sample is then sent to a laboratory for further testing.
In case of respiratory distress syndrome, a chest X-ray is advised. In neonates, the chest X-ray is taken in the supine position. This helps in diagnosing any other related lung disorder. In addition, the examination can be done while the child sleeps and with or without sedation.
How Is Transient Hyperammonemia of The Newborn Managed?
Immediate treatment for this condition is essential to prevent any neurological damage.
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Protein restriction will help in reducing the symptoms.
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Avoid adding amino acids in total parenteral nutrition (TPN), which is feeding nutrition to lower the amino acid level in the body.
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There are two ways through which ammonia detoxification can be done. First is hemodialysis (a dialysis machine that helps in filtering out the blood). It is one of the most effective ways to dispose of excess ammonia. Secondly, medication such as IV Ammonul (sodium benzoate and sodium phenylacetate) helps in balancing the ammonia levels.
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The ammonia level should be monitored continuously, such as neurologic status for signs of central nervous system (CNS) toxicity.
Conclusion
Transient hyperammonemia of the newborn is an idiopathic disorder affecting newborns. The ammonia level is elevated, possibly due to liver failure or any other metabolic disorder. Though this condition is severe, if diagnosed and treated immediately, it may help in a very quick recovery of the newborn.
