Ammonia

Synonym/Acronym:
NH3.

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

Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings
Method: Enzymatic.

AgeConventional UnitsSI Units (Conventional Units × 0.587)
Newborn170–340 mcg/dL100–200 micromol/L
10 d–24 mo70–135 mcg/dL41–79 micromol/L
25 mo–adult15–60 mcg/dL9–35 micromol/L

Critical Findings and Potential Interventions
N/A

Overview

(Study type: Blood collected in completely filled lavender- [EDTA] or green-top [Na or Li heparin] tube; related body system: Digestive system.) Specimen should be transported tightly capped and in an ice slurry. 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.

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.

Interfering Factors

Factors that may alter the results of the study

  • Drugs and other substances that may increase ammonia levels include asparaginase, chlorothiazide, chlorthalidone, fibrin hydrolysate, furosemide, isoniazid, levoglutamide, mercurial diuretics, oral resins, thiazides, and valproic acid.
  • Drugs/organisms and other substances that may decrease ammonia levels include diphenhydramine, kanamycin, monoamine oxidase inhibitors, neomycin, tetracycline, and Lactobacillus acidophilus.
  • Cigarette smoking increases ammonia levels.
  • 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.

Potential Medical Diagnosis: Clinical Significance of Results

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 syndrome (related to insufficient functioning liver cells to metabolize ammonia)
  • Total parenteral nutrition (related to ammonia generated from protein metabolism)

Decreased In:
N/A

Nursing Implications

Potential Nursing Problems Assessment and Nursing Diagnosis

ProblemsSigns and Symptoms
Bleeding (related to altered levels of 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
Confusion (related to an alteration in fluid and electrolytes, hepatic disease and encephalopathy, acute alcohol consumption, hepatic metabolic insufficiency)Disorganized thinking; restlessness; irritability; altered concentration and attention span; changeable mental function over the day; hallucinations; inability to follow directions; disoriented to person, place, time, and purpose; inappropriate affect
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 gray-colored, skin that is flaky with loss of elasticity
Skin (related to jaundice and elevated bilirubin levels, excessive scratching)Jaundiced skin and sclera, dry skin, itching skin, damage to skin associated with scratching

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

  • 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 syndrome in infants.
  • Explain that a blood sample is needed for the test.

After the Study: Potential Nursing Actions

Avoiding Complications

  • Skin: Apply lotion to keep the skin moisturized, avoid alkaline soaps, discourage scratching, apply mittens if patient is unable to follow direction to avoid scratching, administer antihistamines as ordered.

Treatment Considerations

  • Bleeding: 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.
  • 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.

Safety Considerations

  • Confusion: Treat the medical condition; correlate confusion with the need to reverse altered electrolytes; evaluate medications; prevent falls and injury through 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 lactulose as prescribed.

Nutritional Considerations

  • 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. Teach the patient that small, frequent meals throughout the day can increase overall caloric intake and improve nutritional status.
  • Increased ammonia levels may be associated with liver disease. In general, patients should be encouraged to eat a well-balanced diet that includes foods high in fiber. Dietary recommendations will vary depending on the condition and its severity. For example, recommend a diet of soft foods if esophageal varices develop or limitations on salt intake if ascites develop.

Followup Evaluation and Desired Outcomes

  • Accepts the necessity of accurate self-administration of lactulose to reduce absorption of ammonia; decreased blood ammonia level will help prevent hepatic encephalopathy.
  • Acknowledges the importance of making food selections that are appropriate for the degree of liver disease (high protein and high carbohydrate can support nutrition until liver disease prohibits these food selections).
  • Understands that scratching can damage the skin and precipitate an infection.

Ammonia is a sample topic from the Davis's Lab & Diagnostic Tests.

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