Ammonia (NH3): Test Overview, Values, Procedure, Implications, by Nurses Note

  Ammonia (NH3)

Ammonia, an end product of protein metabolism, is formed by bacteria acting on intestinal proteins together with glutamine hydrolysis in the kidneys. The liver normally removes most of this ammonia through the portal vein circulation and converts the ammonia to urea. Because any appreciable level of ammonia in the blood affects the body’s acid-base balance and brain function, its removal from the body is essential. Liver accomplishes this by synthesizing urea so that it can be excreted by the kidneys. 

 Blood ammonia levels are used to diagnose Reye’s syndrome, evaluate metabolism, and determine the progress of severe liver disease and its response to treatment. Blood ammonia measurements are useful in monitoring patients on hyperalimentation therapy. 

Reference Values of  Ammonia (NH 3 )

Normal Values of  Ammonia (NH 3 )

 When measured as NH 3 

 Adults: 15–60 μg/dL or 11–35  μmol/L 

 10 days–2 years: 70–135  μg/dL or 41–80  μmol/L 

 Birth to 10 days: 170–340 μg/dL or 100–200 μmol/L

When measured as N 

 Adults: 15–45 μg/dL or 11–32 μmol/L 

1 month of age: 30–70 μg/dL or 21–50 μmol/L

Birth–14 days: 80–130 μg/dL or 57–93 μmol/L 

＞ 1 month of age: 30–70 g/dL or 21–50 mol/L Birth–14 days: 80–130 g/dL or 57–93 mol/L Values test somewhat higher in capillary blood samples. Values can vary with testing method used. 

Values test somewhat higher in capillary blood samples. Values can vary with the testing method used. 

The procedure of  Ammonia (NH 3 )

 1. Obtain a 5-mL venous plasma sample from a fasting patient. A green-topped (heparin) or purple-topped (EDTA) tube may be used. Observe standard precautions. 

 2. Place the sample in an iced container. The specimen must be centrifuged at 4°C. Promptly remove plasma from cells. Perform the test within 20 minutes or freeze plasma immediately. 

 3. Note all antibiotics the patient is receiving; these drugs lower ammonia levels. 

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Clinical Implications of  Ammonia (NH 3 )

 Increased ammonia levels occur in the following conditions: 

 1. Reye’s syndrome (a potentially fatal disease associated with aspirin use secondary to viral infections primarily in children) 

 2. Liver disease, cirrhosis 

 3. Hepatic coma (does not reflect degree of coma) 

 4. GI haemorrhage 

 5. Renal disease 

 6. HHH syndrome: hyperornithinemia, hyperammonemia, homocitrullinuria 

 7. Transient hyperammonemia of newborn 

 8. Certain inborn errors of metabolism of urea except for argininosuccinic aciduria 

 9. GI tract infection with distention and stasis 

 10. Total parenteral nutrition 

 11. Ureterosigmoidostomy 

Interfering Factors of  Ammonia (NH 3 )

 1. Ammonia levels vary with protein intake and many drugs. 

 2. Exercise may cause an increase in ammonia levels. 

 3. Ammonia levels may be increased by use of a tight tourniquet or by tightly clenching the fist while samples are drawn. 

 4. Ammonia levels can rise rapidly in the blood tubes. 

 5. Hemolyzed blood gives falsely elevated levels. 

Interventions of  Ammonia (NH 3 )

 Pre-test Patient Care 

 1. Explain the test purpose and procedure. Instruct the patient to fast (if possible) for 8 hours before the blood test. Water is permitted. 

 2. Do not allow the patient to smoke for several hours before the test (raises levels). 

 3. Follow guidelines in Chapter 1 regarding safe, effective, informed pretest care. 

Post-test Patient Care 

 1. Interpret test outcomes, monitor appropriately, and begin treatment. 

 2. Remember that in patients with impaired liver function demonstrated by elevated ammonia levels, the blood ammonia level can be lowered by reduced protein intake and by the use of antibiotics to reduce intestinal bacteria counts. 

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