Indications:
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.
Principle:
The ammonia must be normally converted to urea in the liver.
In severe hepatic impairment, this role more and therefore we find there hyperammonemia.
Technique:
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.
Results:
Normal values:
In blood, the usual normal value is from 15 to 50 micromol / L, or 0.3 to 0.8 mg / L.
Pathological changes:
– 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).
Cost:
B50.
Practical advice:
There is no obvious correlation between the rate of ammonia levels and the importance of hepatic encephalopathy.
