Ammonia (NH3), Hyperammonia, Ammonia level
Sample
- Whole blood is needed for the estimation of Ammonia.
- Plasma is prepared in EDTA or heparin other than ammonium heparinate.
- Fasting AM samples are preferred.
- There should be no smoking after 12 midnight.
- Avoid smoking in the vicinity of the test sample place.
- There should be no clinching of the hand.
- Ammonia is a volatile gas, so it should be transported in ice or test immediately.
- The specimen may be centrifuged at 4 °C.
- Perform the test within 20 minutes or freeze the plasma immediately.
- A urine 24 hours sample is preferred.
Precautions
- Analyze the sample as soon as possible.
- Avoid hemolyzed samples increases the ammonia level because the RBCs contain more than three times than plasma.
- Avoid clenching the fist.
- Avoid exercise before taking the blood sample because it increases the level.
- Don’t smoke at least 8 hours before this test.
- One cigarette smoked one hour before the sample can raise the blood ammonia concentration to 100 to 200 µg/L.
- Smokers need a shower and new clothing.
- The technician should also be a non-smoker.
- Use of the tourniquet may increase the ammonia level.
- Avoid contamination of urine by bacteria or ammonia.
- Glassware should be clean and wash with a hypochlorite solution.
- EDTA and heparin are acceptable anticoagulants.
- The arterial blood sample is more reliable than venous but difficult to obtain, so venous blood is taken.
- Drugs that increase the level are:
- Acetazolamide.
- Alcohol.
- Barbiturates.
- Ammonium chloride.
- Narcotics.
- Parenteral nutrition.
- Diuretics.
- Drugs that decrease the level are:
- Broad-spectrum antibiotics (neomycin).
- Levodopa.
- Potassium salt.
- Lactobacillus.
Purpose of the test (Indications)
- To find the progression of liver disease and its response to treatment (Fulminant hepatitis or cirrhosis).
- To diagnose Reye’s syndrome.
- To follow the hepatic encephalopathy.
- In the case of a patient with hyperalimentation, taking high-calorie I/V nutrition.
- The newborn’s advice when the infant has irritability, vomiting, lethargy, and develops seizures in the early days of birth.
Pathophysiology
- The main source of ammonia is skeletal muscles (urea cycle) and the gut, where the ammonia is derived from the intestinal bacteria that breakdown proteins.
- Ammonia is an inorganic compound of hydrogen and nitrogen with the formula of NH 3. It is colorless alkaline gas with a pungent smell.
- Ammonia is irritating gas to the skin, eyes, throat, nose, and lungs.
- Ammonia is the most abundant nitrogen-containing compound in the atmosphere.
- Ammonia is produced in the liver, intestine, and kidneys as the end product of protein metabolism.
- Ammonia is a by-product of protein catabolism.
- The major source of NH3 is the gastrointestinal tract.
- In the hepatic portal vein, NH3 concentration is 5 to 10 times higher than the systemic circulation.
- Most of the ammonia is made by bacteria acting on protein present in the intestine.
- This intestinal ammonia enters the blood and reaches the liver; by way of the portal vein.
- In portal hypertension, ammonia cannot reach the liver to be catabolized.
- The liver converts ammonia into urea, which is then excreted by the kidneys.
- If the liver is damaged, then its level increases in the blood.
- It’s raised level diagnose hepatic encephalopathy, and serial estimation may be done to follow the disease.
- Accumulation of ammonia is toxic to the central nervous system.
- The entry of NH3 into nervous tissue depends upon the pH. As the pH increases, the rate of entry of the NH3 into the nervous tissue increases.
- Ammonia (NH 3) crosses the blood-brain barrier more easily than ammonium (NH 4) ions.
Signs and Symptoms of hyperammonemia:
- Hyperammonemia exerts toxic effects on the central nervous system.
- Causes may be:
- Inherited. The urea cycle enzyme is deficient, common in infants.
- Acquired. The causes are liver diseases and renal failure.
- There is fatigue.
- There is a loss of appetite.
- There are nausea and vomiting.
- There is a loss of strength.
- Ultimately patient will have confusion.
- The patient may have pain abdomen or back.
- Precipitating causes of encephalopathy are:
- Dietary protein.
- Constipation.
- Drugs.
- Infection.
- Electrolytes and acid-base imbalance.
Normal level
Source 2
- Adult = 10 to 80 µg /dL
- Child = 40 to 80 µg /dL
- Newborn = 90 to 150 µg /dL
Other reference
- Normal range = 19 to 60 µg /dL
- Urine = 140 to 1500 µg /dL
Another source
- 19 to 60 µg NH3 /dL (by Du Pont automated clinical analyzer)
- By Ektachem:
- 0 to 10 days = 170 to 341 µg NH3 /dL
- 10 days to 2 years = 68 to 136 µg NH3 /dL
- > 2 years = 19 to 60 µg NH3 /dL
Another source
- Adult = 15 to 56 µg /dL
- Birth to 10 days =109 to 182 µg /dL
- 10 days to 2 years = 95 to 157 µg /dL
- Children = 36 to 85 µg /dL
Raised level is seen in (Hyperammonemia):
- Raised level of ammonia has toxic effects on the nervous system.
- In infants, hyperammonemia may be due to the lack of the urea cycle enzyme.
- Genetic metabolic disorder of the urea cycle.
- The acquired causes of hyperammonemia are:
- Hepatic coma.
- Reye’s syndrome.
- Hemorrhage like GIT (Gastrointestinal) bleeding.
- Gastrointestinal obstruction with mild liver disease.
- Severe congestive heart failure.
- With congestive hepatomegaly.
- Hemolytic diseases of the newborn (HDN).
- Erythroblastosis fetalis.
- Renal diseases.
- Asparagine toxication.
- Portal hypertension.
- Diuretics and antibiotics may increase the ammonia level.
- Alcohol abuse.
- High temperature (Hyperthermia).
- In the case of hypokalemia (low potassium level).
- Metabolic alkalosis.
- Congenital metabolic disorder of the urea cycle.
- Drugs that increase the level are:
- Alcohol.
- Barbiturates.
- Ammonium chloride.
- Acetazolamide.
The decreased level is seen in:
- Essential or malignant hypertension.
- Drugs that decrease the level are:
- Levodopa.
- Broad-spectrum antibiotic (neomycin).
- Potassium salt.
- Lactobacillus.
- Hyperornithinemia.