Bioelectrical impedance analysis in assessment of dry weight in patients on hemodialysis

Background and purpose: Determination of dry weight (DW) in patients undergoing hemodialysis (HD) by means of conventional clinical parameters is unreliable. Bioelectrical impedance analysis (BIA) is a noninvasive method for assessment of body fluid volume. In our study we evaluated the impact of HD on the body fluid changes and the BIA parameters by a direct vector calculation and their correlation with the hemodinamic stability. Subjects and methods: We studied 90 patients (46 women) treated on HD. The BIA and anthropometric measurement were performed at the beginning and at the end of two consecutive HD. A tetrapolar, monofrequency BIA with 50 kHz (BIA-101 Akern/RJL Systems) was performed. The resistance and reactance values were standardized according to the patients' height and were entered into the bivariate vector system and com pared with value for the healthy population. Results and conclusions: Vector displacement in the coordinate system was correlated with the weight changes: the vector was longer and steeper at the end of the HD. Hemodinamically unstable patients (30% of all pis) were in hypervolemia in significantly higher percentage than stable patients before HD (62.9% v 28.6%) and in higher percentage in hypovolemia after HD (48% v 33.2%). We think that a great number of hemodynamically unstable patients is conditioned by an inappropriate clinical assessment of dry weight. BIA enables a precise insight into the hydration state and a realible determination of the DW in patients on HD.