Ammonia is a product of degradation of proteins, it is converted into urea in the liver.
In cases of liver failure, and therefore metabolic transformation, elevation of plasma ammonium observed.
The ammonia must be normally converted to urea in the liver.
In severe hepatic impairment, this role more and therefore we find there hyperammonemia.
Deduction of 1 to 2 mL of venous blood, arterial blood sometimes, on heparinized tube.
Kept on ice, the review must be made within one hour of collection.
The assay is enzymatic.
In blood, the usual normal value is from 15 to 50 micromol / L, or 0.3 to 0.8 mg / L.
– Hyperammonemia is usually due to liver failure, especially if drugs such as barbiturates, opioids or diuretics were taken together;
– But this may also be the result of gastrointestinal bleeding with portal hypertension responsible for increased blood residues;
– It is also a possible complication of caval anastomosis;
– If the hyperammonemia is greater than 200 mmol / L in a newborn, one can fear a enzymopathy the urea cycle, why it is so urgent to establish a proper diet (Rye syndrome).
There is no obvious correlation between the rate of ammonia levels and the importance of hepatic encephalopathy.