Abstract: Objective To assess the ideal dry body weight of maintenance hemodialysis (MHD) patients using multi-frequency bioelectrical impedance analysis (MBIA), and to evaluate the diagnostic value of serum N-terminal pro brain natrinuretic peptide (NT-proBNP) for the volume overload of MHD patients. Methods A total of 105 MHD patients with ideal dry body weight from our blood purification center were enrolled in this study. MBIA was used to obtain the body fluid composition, the ratio of extracellular water (ECW%), and the total body water (TBW), from which the fluid status of the patient was determined. Serum NT-proBNP before
dialysis was also measured. We then analyzed the influence factors for ECW% and the value of serum NT-proBNP for the diagnosis of fluid overload by ROC curve. Results The average ECW% was 0.39±0.01 by MBIA. Using the formula to correct the ECW%, fluid overload was found in 51.4% (54/105) of the patients.
ECW% was positively correlated with age (r= 0.578, P =0.000). ECW% was negatively correlated with gender (r=- 0.251, P=0.010), dehydration volume (r =- 0.226, P=0.020), and diastolic pressure at each time point (r=-0.336, -0.374, -0.281 respectively, and P=0.000, 0.000, 0.004 respectively). Multivariate linear regression showed that age was the independent risk factor for ECW% (β=0.451, t=4.892, P=0.000). Serum NT-proBNP was positively correlated with ECW% (r= 0.340, P =0.000). The median value of serum NT-proBNP was 3,321pg/ml in the patients with ideal dry body weight, and was 5,407pg/ml in the patients without ideal dry body weight (z=-3.802, P =0.000). The ROC curve showed that the area under the curve of serum NTproBNP for the diagnosis of fluid overload was 0.715 (P =0.000); when serum NT-proBNP was set at 3,937pg/ml as the cut-off value for the diagnosis of ideal dry body weight, the sensitivity was 0.704 and the specificity was 0.627. Conclusion Age and serum NT-proBNP level were closely correlated with ECW% in MHD patients. NT- proBNP was a useful marker for evaluating volume status in MHD patient, and NT- proBNP 3, 937pg/ml was the optimal cut-off value for the evaluation of ideal dry body weight.

Key words: Maintenance hemodialysis, Multi- frequency bioelectrical impedance analysis, Ideal dry weight, N-terminal pro brain natrinuretic peptide