Davis's Lab & Diagnostic Tests
B-Type Natriuretic Peptide and Pro-B-Type Natriuretic Peptide
General
Synonym/Acronym:
BNP and proBNP.
Rationale
To assist in diagnosing and managing heart failure (HF).
Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.
Normal Findings
Method: Chemiluminescent immunoassay for BNP; electrochemiluminescent immunoassay for proBNP; enzyme-linked immunosorbent assay for galectin-3 and soluble ST–2.
| BNP | Conventional Units | SI Units (Conventional Units × 1) | |||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Male and Female | Less than 100 pg/mL | Less than 100 ng/L | |||||||||||||||||||||||||||||||||||||||
| proBNP (N-terminal) | |||||||||||||||||||||||||||||||||||||||||
| 0–74 yr | Less than 125 pg/mL | Less than 125 ng/L | |||||||||||||||||||||||||||||||||||||||
| Greater than 75 yr | Less than 449 pg/mL | Less than 449 ng/L | |||||||||||||||||||||||||||||||||||||||
| BNP levels are increased in older adults. | |||||||||||||||||||||||||||||||||||||||||
| Galectin-3 | Less than or equal to 22.1 ng/mL |
| Risk Category | |
| Low | Less than or equal to 17.8 ng/mL |
| Intermediate | 17.9–25.9 ng/mL |
| Elevated | Greater than 25.9 mg/mL |
| Soluble ST–2 | |
| Adult | |
| Male | Less than 52 ng/mL |
| Female | Less than 38.7 ng/mL |
Critical Findings and Potential Interventions
N/A
Overview
(Study type: Blood collected in a lavender-top [EDTA] tube for B-type natriuretic peptide [BNP], plain red-top tube for galectin-3 and soluble ST-2; related body system: Circulatory system.)
The peptides BNP and atrial natriuretic peptide (ANP) are antagonists of the renin-angiotensin-aldosterone system; they assist in the regulation of electrolytes (e.g., BNP inhibits reabsorption of sodium by the kidneys), fluid balance (e.g., increases glomerular filtration rate, thereby increasing urinary excretion), and blood pressure. BNP, proBNP, and ANP are useful markers in the diagnosis of heart failure (HF). BNP, first isolated in the brain of pigs, is a neurohormone synthesized primarily in the ventricles of the human heart in response to increases in ventricular pressure and volume. Circulating levels of BNP and proBNP increase in proportion to the severity of HF. A rapid BNP point-of-care immunoassay may be performed in which a venous blood sample is collected, placed on a strip, and inserted into a device that measures BNP. Results are completed in 10 to 15 min.
Galectin-3 protein levels are considered a prognostic tool in the assessment of diagnosed HF. Elevations in blood specimens greater than 17.8 ng/mL (as measured by enzyme immunoassay) are predictive of increased risk for progression of the disease.
Soluble ST-2 is another prognostic biomarker measured in blood samples, used to predict increased risk for progression of HF—elevations in patients identified with chronic HF predict elevated risk of disease progression. ST-2 is an interleukin family receptor secreted by cardiac muscle in response to mechanical stress. Elevations in blood specimens greater than 35 ng/mL (as measured by enzyme immunoassay) are considered clinically significant.
Coronary artery disease (CAD) and myocardial infarction (MI) are the most common causes of heart disease and most common causes of HF. Hypertension is another significant contributing factor in the development of HF. Other conditions that can contribute to the development or acceleration of HF include anemia, congenital heart defect, diabetes, kidney disease, and thyroid disease. Emphasis on preventive care, including the administration of aspirin, statins, beta blockers, angiotensin-converting enzyme (ACE) inhibitors, and the diuretic aldactone, becomes more important after CAD or MI have been diagnosed to offer protection to the damaged heart muscle.
Patients with advanced HF have few alternatives to extend their lives if a heart transplant is not a timely option. The left ventricular assist device (LVAD), approved by the U.S. Food and Drug Administration, is a system composed of an implanted pump and an external battery-powered pump controller designed to work in unison with the patient’s weakened left ventricle to provide additional blood flow. Implantation of the LVAD is accomplished by open heart surgery.
Indications
- Assist in determining the prognosis and therapy of patients with HF.
- Assist in the diagnosis of HF.
- Assist in differentiating HF from pulmonary disease.
- Cost-effective screen for left ventricular dysfunction; positive findings would point to the need for echocardiography and further assessment.
Interfering Factors
- Age: BNP levels are increased in older adults.
Potential Medical Diagnosis: Clinical Significance of Results
Increased in
BNP is secreted in response to increased hemodynamic load caused by physiological stimuli, as with ventricular stretch or endocrine stimuli from the aldosterone/renin system. Increasing BNP levels would indicate a worsening condition.
- Acute kidney injury
- Cardiac inflammation (myocarditis, cardiac allograft rejection)
- Chronic kidney disease
- Cirrhosis
- Cushing syndrome
- Heart failure
- Kawasaki disease
- Left ventricular hypertrophy
- Myocardial infarction
- Primary hyperaldosteronism
- Primary pulmonary hypertension
- Ventricular dysfunction
Decreased in
Decreasing BNP levels would indicate improvement.
Nursing Implications, Nursing Process, Clinical Judgement
Potential Problems: Assessment & Nursing Diagnosis/Analysis
| Problems | Signs and Symptoms |
|---|---|
| Cardiac output (decreased—related to altered preload [increased/decreased], increased afterload, impaired cardiac contractility, cardiac muscle disease, altered cardiac conduction, side effects of medication) | Decreased peripheral pulses; decreased urinary output; cool, clammy skin; tachypnea; dyspnea; edema; altered level of consciousness; abnormal heart sounds; crackles in lungs; decreased activity tolerance; weight gain; edema; fatigue; hypoxia; hypotension |
| Gas exchange (inadequate—related to altered alveolar and capillary exchange secondary to fluid in the alveoli) | Decreased activity tolerance, increased shortness of breath with activity, weakness, orthopnea, cyanosis, cough, increased heart rate, weight gain, edema in the lower extremities, increased respiratory rate, use of respiratory accessory muscles |
Before the Study: Planning and Implementation
Teaching the Patient What to Expect
- Discuss how this test can assist in diagnosing HF.
- Explain that a blood sample is needed for the test.
After the Study: Implementation & Evaluation Potential Nursing Actions
Treatment Considerations
- Inadequate tissue perfusion can be a concern. Symptoms of inadequate tissue perfusion include hypotension, dizziness, cool extremities, capillary refill greater than 3 sec, weak pedal pulses, and altered level of consciousness.
- Interventions/actions related to inadequate tissue perfusion include the following: Assess dizziness, pedal pulses, delayed capillary refill, and skin for pallor and warmth. Monitor blood pressure for hypotension and heart for increased rate and skipped beats. Monitor for sensorium changes, confusion, stupor, lethargy, coma, as well as restlessness and anxiety.
- Fluid volume excess can be a concern. Symptoms of fluid volume excess include edema, shortness of breath, increased weight, ascites, rales, rhonchi, diluted laboratory values, increased blood pressure, positive jugular venous distention (JVD), orthopnea, cough, restlessness, tachycardia, pulmonary congestion with x-ray, ascites, hypertension, and decreased urinary output.
- Interventions/actions related to fluid volume excess include the following: Assess for peripheral edema (legs, feet, ankles, sacrum) and JVD. Assess for shortness of breath and adventitious lung sounds, such as crackles. Measure daily weight with notation of trends. Monitor blood pressure, heart rate, and intake versus output. Monitor laboratory values that reflect alterations in fluid status and manage underlying cause of fluid alteration. Administer prescribed diuretics, restrict sodium intake, and order a low-sodium diet. Limit fluid intake as appropriate.
Cardiac Output
- Facilitate management of decreased cardiac output.
- Interventions/actions related to decreased cardiac output include the following: Assess peripheral pulses and capillary refill. Assess respiratory rate, breath sounds, orthopnea, skin color, temperature, moisture, and level of consciousness. Assess heart sounds for abnormal beats. Assess for shortness of breath with activity. Monitor blood pressure and check for orthostatic changes (dizziness) related to fluid loss. Monitor urinary output, sodium and potassium levels, BNP levels, and other prognostic test results. Administer ordered oxygen and use pulse oximetry to monitor oxygen saturation. Administer ordered medications: aldosterone antagonists, ACE inhibitors, beta blockers, diuretics, inotropic drugs, and vasodilators. Adjust fluids for decreased cardiac preload or increased cardiac preload as ordered.
Gas Exchange
- Facilitate management of inadequate gas exchange.
- Interventions/actions related to inadequate gas exchange include the following: Assess respiratory rate. Auscultate and trend breath sounds. Administer ordered oxygen, monitor saturation with pulse oximetry. Collaborate with the health-care provider (HCP) to consider intubation and/or mechanical ventilation. Monitor potassium levels. Place the head of the bed in high Fowler position to facilitate breathing. Administer ordered diuretics and vasodilators.
Nutritional Considerations
- Recommend consultation with a registered dietitian. Consider cultural implications of diet recommendations. Discuss the value of variety in food choices within the basic food groups. Limit salt intake to 2,000 mg/day. Limit or abstain from alcohol intake.
- Consume foods high in potassium when taking diuretics to offset loss of potassium: bananas, strawberries, oranges; cantaloupes; green leafy vegetables, such as spinach and broccoli; dried fruits such as dates, prunes, and raisins; legumes such as peas and pinto beans; nuts and whole grains.
- Consume foods high in fiber (25–35 g/day).
- Maintain a healthy weight. Be physically active. Consider abstaining from smoking.
Clinical Judgement
- Consider how to facilitate adherence to dietary changes as a valuable therapeutic tool.
Followup Evaluation and Desired Outcomes
- Details the purpose of taking prescribed medications: diuretic, ACE inhibitor, and/or beta blocker.
- Acknowledges the importance of limiting fluids to decrease cardiac stress, including strategies to limit fluid intake and notify the HCP of excessive weight gain.
- Safely self-administers ordered oxygen and can state symptoms of hypoxia reportable to the HCP.
- Demonstrates how to keep an accurate intake and output and acknowledges the importance of a daily weight to monitor fluid fluctuations.
- Understands the importance of reporting life-threatening changes, such as cool extremities, pallor, and diaphoresis, to HCP immediately.
