From the Guidelines
Dialysis patients can indeed have elevated Brain Natriuretic Peptide (BNP) levels, even in the absence of heart failure, due to reduced renal clearance and other factors. The kidneys play a significant role in eliminating BNP from circulation, and in patients with end-stage renal disease (ESRD) on dialysis, this clearance is impaired 1. According to the study published in the European Heart Journal, acute or chronic renal failure is one of the diseases that can increase natriuretic peptides, including BNP 1.
Some key points to consider when interpreting BNP levels in dialysis patients include:
- Reduced renal clearance of BNP, which leads to higher levels in patients with end-stage renal disease (ESRD) on dialysis
- Concurrent cardiac conditions like left ventricular hypertrophy or subclinical heart failure that contribute to increased BNP production
- Fluid overload between dialysis sessions, which can stimulate BNP release
- The need to use higher threshold values for BNP levels in dialysis patients compared to those with normal kidney function, with levels of 200-300 pg/mL or higher potentially being more appropriate cutoffs
It's also important to note that serial measurements tracking changes in BNP over time are often more valuable than absolute values in these patients, as relying on standard BNP reference ranges could lead to overdiagnosis of heart failure 1. The study highlights that N-terminal proB-type natriuretic peptide (NT-proBNP) renal extraction is maintained in the presence of moderate kidney dysfunction, but in cases of severe renal dysfunction, NT-proBNP/BNP ratios increase for unclear reasons 1.
Overall, when evaluating dialysis patients for potential cardiac issues, it's crucial to consider these factors and interpret BNP levels in the context of the patient's overall clinical picture, rather than relying solely on standard reference ranges.
From the Research
Elevated BNP in Dialysis Patients
- Dialysis patients can have elevated Brain Natriuretic Peptide (BNP) levels due to various factors such as fluid overload, left ventricular hypertrophy, and heart failure 2, 3, 4.
- Studies have shown that BNP levels are frequently elevated in dialysis patients, and this elevation is associated with increased mortality risk 3, 4.
- The interpretation of BNP levels in dialysis patients is confounded by impaired renal clearance and preexisting left ventricular abnormalities, which limits their applicability as a surrogate marker of volume status 2.
Factors Influencing BNP Levels
- Fluid overload is a significant factor influencing BNP levels in dialysis patients, and correction of fluid overload can lead to a decrease in BNP levels 3, 5.
- Cardiac history and left ventricular dysfunction also play a crucial role in determining BNP levels in dialysis patients 3, 4.
- The type and frequency of dialysis can also impact BNP levels, with daily dialysis showing a decrease in predialysis BNP levels compared to conventional thrice-weekly dialysis 6.
Clinical Utility of BNP
- BNP can be a useful diagnostic and prognostic tool in dialysis patients, helping to identify those at risk of cardiovascular morbidity and mortality 2, 3, 5.
- Measuring plasma BNP levels can aid in the identification of dialysis patients with left ventricular hypertrophy and dysfunction 4.
- NT-pro BNP, a related biomarker, has also been shown to be a predictive factor for volume overload in hemodialysis patients with or without left ventricular dysfunction 5.