title: Association between brain natriuretic peptide and extracellular water in hemodialysis patients.
abstract: BACKGROUND
  Brain natriuretic peptide (BNP) is a hormone released by the left ventricle (LV) as a consequence of pressure or volume load. BNP increases in left ventricle hypertrophy (LVH), LV dysfunction, and it can also predict cardiovascular mortality in the general population as well as those undergoing hemodialysis (HD). We investigated the association between BNP and volume load in HD patients.
  
  
  METHODS
  We studied 32 HD patients (60 +/- 17.1 years) treated thrice-weekly for at least 6 months. Exclusion criteria were: LV dysfunction, atrial fibrillation, malnutrition. Blood chemistries and BNP were determined on mid-week HD day. Blood pressure (BP) and cardiac diameters were determined on mid-week inter-HD day by using 24-hour ambulatory blood pressure monitoring and echocardiography. Bioimpedance was performed after HD and extracellular water (ECW%), calculated as a percentage of total body water, was considered as the index of volume load.
  
  
  RESULTS
  Patients were divided into quartiles of 8 patients depending on the BNP value: 1st qtl BNP < or =45.5 pg/ml (28.4 +/- 10.9 pg/ml), 2nd qtl BNP > 45.5 pg/ml and < or =99.1 pg/ml (60.9 +/- 15.8 pg/ml), 3rd qtl BNP > 99.1 pg/ml and < or =231.8 pg/ml (160.5 +/- 51.8 pg/ml), 4th qtl BNP > 231.8 pg/ml (664.8 +/- 576.6 pg/ml). No inter-quartile differences were reported in age, HD age, body mass index spKt/V, or blood chemistries. As expected patients in the 4th BNP quartile showed the highest values of 24-hour pulse pressure (PP) and LV mass index (LVMi). The study of body composition revealed significant differences in ECW%, which was higher in the 4th quartile when compared to the others (4th q: 50 +/- 9.6%, vs 1st q. 40.1 +/- 2.4%, 2nd q. 41.9 +/- 5%, 3rd q. 42.8 +/- 6.9%). Using multiple stepwise linear regression where BNP was the dependent variable, and PP and ECW% the independent variables, only ECW% maintained statistical significance as a predictor of BNP levels (PP: Beta = 0.86, p = 0.58; ECW%: Beta = 0.64, p < 0.001 p < 0.001).
  
  
  CONCLUSIONS
  Few studies have investigated the relationship between plasma BNP and volume load, and direct evidence is lacking. We used bioimpedance and the determination of ECW% to assess volume state in HD patients finding an association between BNP and ECW. The increased synthesis and release of BNP from the LV in HD patients appear to be mainly related to volume stress rather than to pressure load.
authors: Nephrology-Dialysis Department, Ospedale Silvestrini, Azienda Ospedaliera di Perugia, Perugia, Italy. rmfag@tin.it
authors: Riccardo Maria
authors: RM
authors: Fagugli
authors: Barbara
authors: B
authors: Palumbo
authors: Daniela
authors: D
authors: Ricciardi
authors: Paolo
authors: P
authors: Pasini
authors: Paola
authors: P
authors: Santirosi
authors: Luigi
authors: L
authors: Vecchi
authors: Franca
authors: F
authors: Pasticci
authors: Renato
authors: R
authors: Palumbo
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure / Q000502:physiology; D001834:Body Water; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D045604:Extracellular Fluid; D005260:Female; D006801:Humans; D017379:Hypertrophy, Left Ventricular / Q000473:pathology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000097:blood*; D006435:Renal Dialysis
chemical_list: D015415:Biomarkers; D020097:Natriuretic Peptide, Brain