B-Type Natriuretic Peptide and Pro-B-Type Natriuretic Peptide

Synonym/Acronym:
BNP and proBNP.

Rationale
To assist in diagnosing 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.

BNPConventional UnitsSI Units (Conventional Units × 1)
Male and FemaleLess than 100 pg/mLLess than 100 ng/L
proBNP (N-terminal)
0–74 yrLess than 125 pg/mLLess than 125 ng/L
Greater than 75 yrLess than 449 pg/mLLess than 449 ng/L
BNP levels are increased in older adults.

Critical Findings and Potential Interventions
N/A

Overview

(Study type: Blood collected in a lavender-top [EDTA] tube; related body system: Circulatory system.) The peptides B-type natriuretic peptide (BNP) and atrial natriuretic peptide (ANP) are antagonists of the renin-angiotensin-aldosterone system; they assist in the regulation of electrolytes, fluid balance, 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 heart failure. 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. Conditions that can contribute to the development or acceleration of HF include anemia, congenital heart defect, diabetes, hypertension, kidney disease, and thyroid disease.

Indications

  • Assist in determining the prognosis and therapy of patients with heart failure.
  • Assist in the diagnosis of heart failure.
  • Assist in differentiating heart failure from pulmonary disease.
  • Cost-effective screen for left ventricular dysfunction; positive findings would point to the need for echocardiography and further assessment.

Interfering Factors

Contraindications

Patients receiving nesiritide. Nesiritide (Natrecor) is a recombinant form of BNP that may be given therapeutically by IV to patients in acutely decompensated heart failure; with some assays, BNP levels may be transiently and significantly elevated at the time of administration and must be interpreted with caution. The testing laboratory should be consulted to verify whether test measurements are affected by nesiritide.

Factors that may alter the results of the study

  • 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

Potential Nursing Problems Assessment and Nursing Diagnosis

ProblemsSigns and Symptoms
Cardiac output (related to increased preload, increased afterload, impaired cardiac contractility, cardiac muscle disease, altered cardiac conduction)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; fatigue; hypoxia
Excess fluid volume (related to altered cardiac output)Edema; shortness of breath; increased weight; ascites, rales, and rhonchi; diluted laboratory values; increased blood pressure; positive jugular venous distention (JVD); orthopnea; cough; restlessness; tachycardia; pulmonary congestion with x-ray
Gas exchange (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
Tissue perfusion (related to compromised cardiac contractility, interrupted blood flow)Hypotension, dizziness, cool extremities, capillary refill greater than 3 sec, weak pedal pulses, altered level of consciousness

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

  • Inform the patient this test can assist in diagnosing heart failure.
  • Explain that a blood sample is needed for the test.

After the Study: Potential Nursing Actions

Treatment Considerations

  • Cardiac Output: Assess peripheral pulses and capillary refill. Monitor blood pressure and check for orthostatic changes (dizziness) related to fluid loss. Assess respiratory rate, breath sounds, orthopnea, skin color and temperature, and level of consciousness. Monitor urinary output, sodium and potassium levels, and BNP levels. Administer ordered oxygen and use pulse oximetry to monitor oxygenation. Administer ordered medications aldosterone antagonists, angiotensin-converting enzyme (ACE) inhibitors, beta blockers, diuretics, inotropic drugs, and vasodilators. Explain the importance of taking prescribed medications to support cardiac health.
  • Excess Fluid Volume: Daily weight with monitoring of trends. Limit fluid as appropriate. Assess for peripheral edema, JVD, adventitious lung sounds such as crackles. Monitor blood pressure, heart rate, and intake versus output. Administer prescribed diuretics, restrict sodium intake, and order a low-sodium diet. Monitor laboratory values that reflect alterations in fluid status and manage underlying cause of fluid alteration.
  • Gas Exchange: Auscultate and trend breath sounds. Assess respiratory rate and administer ordered oxygen with pulse oximetry to monitor oxygenation. Collaborate with the health-care provider (HCP) to consider intubation and/or mechanical ventilation as appropriate. Place the head of the bed in high Fowler position. Administer ordered diuretics and vasodilators. Monitor potassium levels.
  • Tissue Perfusion: Monitor blood pressure. Assess for dizziness, pedal pulses, capillary refill, and skin temperature for warmth.

Nutritional Considerations

  • Instruct patients to consume a variety of foods within the basic food groups, eat foods high in potassium when taking diuretics, eat a diet high in fiber (25–35 g/day), maintain a healthy weight, be physically active, limit salt intake to 2,000 mg/day, limit alcohol intake, and be a nonsmoker.
  • Recommend consultation with a registered dietitian. High-potassium foods (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) can offset the loss of potassium from taking diuretics. Emphasize limiting dietary salt to recommended daily amount.

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.
  • Safely self-administers ordered oxygen.
  • 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.

B-Type Natriuretic Peptide and Pro-B-Type Natriuretic Peptide is a sample topic from the Davis's Lab & Diagnostic Tests.

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