From the Guidelines
Yes, B-type Natriuretic Peptide (BNP) can be used to assess for fluid retention, particularly in the context of heart failure. BNP is a hormone released by the heart ventricles in response to stretching of heart muscle cells due to increased volume or pressure. When fluid accumulates in the body, it increases blood volume and pressure in the heart chambers, triggering BNP release. According to the most recent and highest quality study 1, BNP levels can help clinicians distinguish between cardiac and non-cardiac causes of dyspnea, monitor treatment effectiveness for heart failure, and guide diuretic therapy.
Key Points to Consider
- Normal BNP levels are typically below 100 pg/mL, with levels above 400 pg/mL strongly suggesting heart failure with fluid overload.
- Values between 100-400 pg/mL represent a gray zone requiring clinical correlation.
- The related NT-proBNP test works similarly but has different reference ranges (normal <300 pg/mL for those under 75 years).
- BNP levels should be used as part of a comprehensive clinical assessment rather than in isolation when evaluating fluid status.
- Interpretation requires consideration of other factors that can affect levels, including age, kidney function, obesity (which can lower values), and certain medications.
Clinical Application
BNP levels can be useful in establishing the prognosis or disease severity in outpatients with chronic heart failure, as well as in hospitalized patients with acutely decompensated heart failure 1. However, the usefulness of serial measurement of BNP or NT-proBNP to reduce hospitalizations or mortality in patients with heart failure has not been established.
Limitations and Future Directions
While BNP is a valuable tool in assessing fluid retention, its interpretation requires careful consideration of various factors that can influence its levels. Further research is needed to fully understand the role of BNP in guiding therapy and improving outcomes in patients with heart failure.
From the Research
BNP and Fluid Retention Assessment
- B-type Natriuretic Peptide (BNP) is a biomarker that can be used to assess fluid retention, as it is secreted by cardiomyocytes in response to increased mechanical load and wall stretch 2.
- High BNP levels are associated with fluid overload and decreased patient survival in heart failure patients and hemodialysis patients 3.
- BNP levels can be used to evaluate hydration status correction after hemodialysis onset, and the decrease in BNP levels in the first months of hemodialysis therapy is related to fluid excess correction 3.
- The plasma concentration of BNP is raised in various pathological states, especially heart failure, and can be used to exclude a diagnosis of heart failure in patients with dyspnea or fluid retention 4.
Relationship between BNP and Fluid Status
- There is a strong link between the appearance of clinical signs of fluid retention and an increased BNP level in patients with chronic heart failure 5.
- BNP levels reliably reflect both decompensation and improvement in the patient's condition, despite wide intraindividual fluctuations in BNP over time 5.
- BNP levels are highly correlated with clinical parameters such as New York Heart Association functional class, left ventricular ejection fraction, and peak oxygen consumption 6.
Clinical Utility of BNP
- BNP can be used as a sensitive biomarker of cardiac dysfunction and heart failure, and can help guide therapy and predict prognosis 2, 4.
- Rapid measurement of BNP levels is comparable to conventional BNP measurement and can be used to stratify patients with chronic heart failure 6.
- BNP levels can be used to identify patients with left ventricular systolic dysfunction, with a high sensitivity and specificity 6.