Brain natriuretic peptide and N-terminal proBNP in chronic haemodialysis patients

Brain natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) are released into circulation as a result of congestive heart failure (HF). As HF and water overload are frequent complications in haemodialysis (HD) patients, we decided to study the levels of BNP and NT-proBNP and their changes during HD.

BNP and NT-proBNP levels were determined in 94 HD patients before and after a regular 4-h HD. We followed changes in these peptides during HD depending on age, sex, HF (NYHA classification and left ventricular ejection fraction [LVEF]), duration on HD, presence of hypertension, coronary artery disease, type of membrane used for HD [low-flux (LFx) or high-flux (HFx)] and body mass change during HD. Furthermore, patients basic medication and creatinine levels and presence of diabetes mellitus were monitored.

Respectively,94% and 100% of the patients had pre-dialysis concentrations of BNP and NT-proBNP above the cut-off values for HF. The marker levels correlated significantly both before and after HD (r = 0.903 and 0.888, respectively, p < 0.001). BNP levels significantly decreased (p < 0.0001), whereas NT-proBNP significantly increased (p < 0.0001) during HD on LFx membranes. HD on HFx membranes caused greater decrease of BNP (compared to LFx membranes, p < 0.001), but also a decrease of NT-proBNP (p < 0.001).We did not find any significant differences in marker levels for HF and non-HF patients (NYHA classification). However, both peptides reached higher levels in the group with LVEF < or = 50% (p < 0.001 for both peptides). Body mass change during HD negatively correlated only with the change of NT-proBNP (r = -0.27, p < 0.05). In the multiple regression model, the change of both peptides during HD was significantly influenced by membrane type (p = 0.003 for BNP and p = 0.001 for NT-proBNP). NT-proBNP change during HD was further significantly influenced by LVEF (p = 0.012), sex (p = 0.002) and duration on HD (p = 0.006).

Both BNP and NT-proBNP levels were significantly increased in HD patients prior to dialysis. The change in concentrations of both peptides during HD is influenced by membrane type. HD probably triggers increased production of both peptides and this increase is emphasized by impaired LVEF. This fact can be clinically observed only on NT-proBNP levels, because BNP levels are biased by significant removal of this protein during HD.