Ammonia
Synonyms - Specimen - Reference Value - Method - Description - Indications - Interpretation
Synonyms : NH3
Specimen : Plasma collected in completely filled ( heparin ) tube .Specimen should be transported tightly capped and in an ice slurry .
Reference Value : Adults 19 - 60 micron g/dL
Method : spectrophotometry
Description
Blood ammonia ( NH3 ) comes from two sources
a - Deamination of amino acids during protein metabolism.
b - Degradation of proteins by colon bacteria .
The liver converts ammonia in the portal blood to urea , which is excreted by kidneys . When liver function is severely compromised , especially in situations in which decreased hepatocellular function is combined with impaired portal blood flow , ammonia levels rise .
Ammonia is potentially toxic to the central nervous system
Indications
- Evaluated advanced liver disease
- Identify impending hepatic encephalopathy with known liver disease
Interpretation
Increased in
1 - Gastrointestinal hemorrhage
2- Genitourinary tract infection with distention and stasis ( urea-splitting urinary tract infection )
3 - Urea cycle metabolism defects
4 - Hepatic coma
5 - Liver failure , late cirrhosis
6 - Total parenteral nutrition
7 - Portacaval shunting