Hyperammonemia
Hyperammonemia Causes
Hyperammonemia has multiple causes, generally as a result of enzyme deficiencies in the urea cycle. Primary hyperammonemia results from several inborn abnormalities of the metabolism caused by low activities of enzymes in the urea cycle. Secondary hyperammonemia, on the other hand, results in inborn metabolic errors caused by abnormally low activities of enzymes outside the urea cycle. Examples of this are Propionic acidemia and Methylmalonic acidemia. Secondary hyperammonemia is often caused by the metabolic cell dysfunctions.
Hyperammonemia Definition
Hyperammonemia, also known as hyperammonaemia, is a type of metabolic defect marked by high levels of ammonia in the blood. Hyperammonemia can be a fatal condition which can easily lead to encephalopathy and eventual death.
Hyperammonemia Diagnosis
Lab tests to determine plasma ammonia levels are often done when symptoms indicate hyperammonemia. Plasma amino acid level quantitation is also done if genetic causes are suspected. A urinary organic acid profile is used to determine metabolic deficiencies where hyperammonemia is a secondary result. This study can help determine levels in propionic acid, methylmalonic acid, isovaleric acid, or other organic acids. In addition, screening tests to determine urine amino acid levels, blood lactate levels, blood gas levels, BUN levels, and N-carbamoyl-L-glutamic acid in infants are also particularly helpful in diagnosis.
Hyperammonemia Symptoms and Signs
In general, hyperammonemia patients show poor physical growth and hypothermia. Head, ears, eyes, nose, and throat infections may be present in cases where cerebral edema and high intracranial pressure have occurred. Hyperammonemia may also result in several pulmonary problems; including tachypnea or hyperpnea, as well as apnea and respiratory failure in late stages. In additional, abdominal disorders may also occur. Particularly evident are neurologic symptoms ? including poor limb coordination, dysdiadochokinesia, hypertonia, ataxia, intermittent tremors and seizures, lethargy, as well as decorticate or decerebrate posturing.
Hyperammonemia Treatment
Initial treatment for hyperammonemia includes the immediate restriction of protein and certain specific amino acids. Stopping protein intake is imperative in early management. To compensate for the protein loss, several nonprotein calories can be administered via intravenous or oral means, or both. More specific treatments will depend on the specific cause of the disorder. In some cases, there is a need for Hemodialysis, intravenous sodium phenylacetate/benzoate (Ammonul), or both.