NH3

ammonia

Biochemistry
An irritating, water-soluble, strongly basic, colourless gas, which is lighter than air.

Industry
Ammonia (NH3) is used in explosives, fertilisers, refrigerants and household cleaning solutions.

Physiology
NH3 is produced in the liver, intestine and kidneys as an end-product of protein metabolism; the liver converts ammonia into urea, which is then excreted by the kidneys; in liver disease this conversion is decreased, resulting in increased serum ammonia. Serial measurement of ammonia is used to follow progression of hepatic encephalopathy in Reye syndrome and other conditions.

Ref range
15–49 µg/dL.

Abnormal values
Increased hepatic coma, Reye syndrome, severe CHF, GI haemorrhage, erythroblastosis fetalis, drugs (e.g., diuretics and antibiotics).

NH₃

Abbreviation for ammonia.

Ammonia

Synonym/acronym: NH₃.

Common use

To assist in diagnosing liver disease such as hepatitis and cirrhosis and evaluating the effectiveness of treatment modalities. Specifically used to assist in diagnosing infant Reye’s syndrome.

Specimen

Plasma (1 mL) collected in completely filled lavender- (EDTA) or green-top (Na or Li heparin) tube. Specimen should be transported tightly capped and in an ice slurry.

Normal findings

(Method: Enzymatic)

Age	Conventional Units	SI Units (Conventional Units × 0.587)
Newborn	170–340 mcg/dL	100–200 micromol/L
10 d–24 mo	68–136 mcg/dL	40–80 micromol/L
25 mo–Adult	19–60 mcg/dL	11–35 micromol/L

Description

Blood ammonia (NH₃) comes from two sources: deamination of amino acids during protein metabolism and degradation of proteins by colon bacteria. The liver converts ammonia in the portal blood to urea, which is excreted by the 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. Congenital enzyme defects that prevent the breakdown of ammonia or conditions that affect the ability of the kidneys to excrete ammonia can also result in increased blood levels. Ammonia is potentially toxic to the central nervous system and may result in encephalopathy or coma if toxic levels are reached.

This procedure is contraindicated for

N/A

Indications

Evaluate advanced liver disease or other disorders associated with altered serum ammonia levels
Identify impending hepatic encephalopathy with known liver disease
Monitor the effectiveness of treatment for hepatic encephalopathy, indicated by declining levels
Monitor patients receiving hyperalimentation therapy

Potential diagnosis

Increased in

Gastrointestinal hemorrhage (related to decreased blood volume, which prevents ammonia from reaching the liver to be metabolized)
Genitourinary tract infection with distention and stasis (related to decreased renal excretion; levels accumulate in the blood)
Hepatic coma (related to insufficient functioning liver cells to metabolize ammonia; levels accumulate in the blood)
Inborn enzyme deficiency (evidenced by inability to metabolize ammonia)
Liver failure, late cirrhosis (related to insufficient functioning liver cells to metabolize ammonia)
Reye’s syndrome (related to insufficient functioning liver cells to metabolize ammonia)
Total parenteral nutrition (related to ammonia generated from protein metabolism)

Decreased in

N/A

Critical findings

N/A

Interfering factors

Drugs that may increase ammonia levels include asparaginase, chlorthiazide, chlorthalidone, fibrin hydrolysate, furosemide, hydroflumethiazide, isoniazid, levoglutamide, mercurial diuretics, oral resins, thiazides, and valproic acid.
Drugs/organisms that may decrease ammonia levels include diphenhydramine, kanamycin, monoamine oxidase inhibitors, neomycin, tetracycline, and Lactobacillus acidophilus.
Hemolysis falsely increases ammonia levels because intracellular ammonia levels are three times higher than plasma.
Prompt and proper specimen processing, storage, and analysis are important to achieve accurate results. The specimen should be collected on ice; the collection tube should be filled completely and then kept tightly stoppered. Ammonia increases rapidly in the collected specimen, so analysis should be performed within 20 min of collection.

Nursing Implications and Procedure

Potential nursing problems

Problem	Signs & Symptoms	Interventions
Confusion (Related to an alteration in fluid and electrolytes, hepatic disease and encephalopathy; acute alcohol consumption; hepatic metabolic insufficiency)	Disorganized thinking, restless, irritable, altered concentration and attention span, changeable mental function over the day, hallucinations; altered attention span; unable to follow directions; disoriented to person, place, time, and purpose; inappropriate affect	Treat the medical condition; correlate confusion with the need to reverse altered electrolytes; evaluate medications; prevent falls and injury through appropriate use of postural support, bed alarm, or the appropriate use of restraints; consider pharmacological interventions; track accurate intake and output to assess fluid status; monitor blood ammonia level; determine last alcohol use; assess for symptoms of hepatic encephalopathy such as confusion, sleep disturbances, incoherence; protect the patient from physical harm; administer lactose as prescribed
Nutrition (Related to excess alcohol intake; insufficient eating habits; altered liver function)	Known inadequate caloric intake; weight loss; muscle wasting in arms and legs; stool that is pale or grey colored; skin that is flaky with loss of elasticity	Document food intake with possible calorie count; assess barriers to eating; consider using a food diary; monitor continued alcohol use as it is a barrier to adequate protein nutrition; monitor glucose levels; monitor daily weight; perform dietary consult with assessment of cultural food selections
Skin (Related to jaundice and elevated bilirubin levels; excessive scratching)	Jaundiced skin and sclera; dry skin; itching skin; damage to skin associated with scratching	Application of lotion to keep the skin moisturized; avoid alkaline soaps; discourage scratching; apply mittens if patient is not able to follow direction to avid scratching; administer antihistamines as ordered
Bleeding (Related to alerted clotting factors; portal hypertension; esophageal bleeding)	Altered level of consciousness; hypotension; increased heart rate; decreased HGB and HCT; capillary refill greater than 3 sec; cool extremities	Increase frequency of vital sign assessment with variances in results; monitor for vital sign trends; administer blood or blood products as ordered; administer stool softeners as needed; encourage intake of foods rich in vitamin K; avoid foods that may irritate esophagus

Pretest

Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
Patient Teaching: Inform the patient this test can assist with the evaluation of liver function related to processing protein waste. May be used to assist in diagnosis of Reye’s syndrome in infants.
Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
Obtain a history of the patient’s gastrointestinal, genitourinary, and hepatobiliary systems; symptoms; and results of previously performed laboratory tests and diagnostic and surgical procedures.
Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
Note that there are no food, fluid, or medication restrictions unless by medical direction.

Intratest

Potential complications: N/A
Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess the venipuncture site for bleeding or hematoma formation and secure the gauze with adhesive bandage.
Promptly transport the specimen to the laboratory for processing and analysis. The tightly capped sample should be placed in an ice slurry immediately after collection. Information on the specimen label should be protected from water in the ice slurry by first placing the specimen in a protective plastic bag.

Post-Test

Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure. Recognize anxiety related to test results, and carefully observe the cirrhotic patient for the development of ascites, in which case fluid and electrolyte balance require strict attention. Dietary and fluid restrictions may be required; diuretics may be ordered. The patient should be frequently monitored for weight gain, intake and output, and abdominal girth. The alcoholic patient should be encouraged to avoid alcohol and also to seek appropriate counseling for substance abuse.
Nutritional Considerations: Increased ammonia levels may be associated with liver disease. Dietary recommendations may be indicated, depending on the severity of the condition. A low-protein diet may be in order if the patient’s liver has lost the ability to process the end products of protein metabolism. A diet of soft foods may be required if esophageal varices have developed. Ammonia levels may be used to determine whether protein should be added to or reduced from the diet. Patients should be encouraged to eat simple carbohydrates and emulsified fats (as in homogenized milk or eggs) rather than complex carbohydrates (e.g., starch, fiber, and glycogen [animal carbohydrates]) and complex fats, which would require additional bile to emulsify them so that they could be used.
Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.
Patient Education
- Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP.
- Answer any questions or address any concerns voiced by the patient or family.
- Teach the patient that small frequent meals throughout the day can increase overall caloric intake and improve nutritional status.
- Teach the patient that scratching can damage the skin and precipitate an infection.
Expected Patient Outcomes
- Knowledge
- Discusses that adherence to eating several small meals can improve caloric intake
- Associates compliance with taking lactalose with decreased blood ammonia level to help prevent hepatic encephalopathy
- Skills
- Modifies the diet and selects foods that are appropriate for the degree of liver disease (high protein and high carbohydrate can support nutrition until liver disease prohibits these food selections)
- Accurately self-administers lactalose as prescribed to reduce absorption of ammonia
- Attitude
- Resolves to participate in counseling for alcohol abuse
- Follows the recommendations of the physician and family members in supporting positive health decisions

Related Monographs

Related tests include ALT, albumin, analgesic, anti-inflammatory, and antipyretic drugs (acetaminophen and acetylsalicylic acid), anion gap, AST, bilirubin, biopsy liver, blood gases, BUN, blood calcium, CT biliary tract and liver, CT pelvis, cystometry, cystoscopy, EGD, electrolytes, GI blood loss scan, glucose, IVP, MRI pelvis, ketones, lactic acid, Meckle’s scan, osmolality, protein, PT/INR, uric acid, and US pelvis.
See the Gastrointestinal, Genitourinary, and Hepatobiliary systems tables at the end of the book for related tests by body system.

NH3