Using Bioelectrical Impedance Vector Analysis Method Estimate the Hydration State during Hemodialysis

Objective: This investigation employed bioelectrical impedance vector analysis (BIVA) method to observed the hydration of patients undergoing hemodialysis process and to understand the quality of water control inter-dialysis. Method: Sixty chronic hemodialysis patients were randomly selected (20 males, aged 62±12.5, and 40 females, aged 65±9.5). This study used a multifrequency bioelectrical impedance analyzer to detect the resistance and reactance of a patient at start and end on dialysis process and to obtain Z-graph drawn on two axes resistance and reactance normalized by each subject's height individually. Then, according to patients' conditions, such as gender, weight, and whether they had diabetes or not, vectors relative to these conditions were compared on the Z-graph to know hydration state. Results: Distributions of vectors obtained forms pre-/post-dialysis on the Z-graph could be observed, which all located along the major axis from the lower-left to upper-right of the plane under all conditions like gender, weight, and whether they had diabetes or not. On different genders, vectors located along the minor axis from the lower-right to upper-left of the plane relative to the condition from lean to obese. Conclusion: From the direction and location of vectors on the Z-graph, we could learn that the hydration state of different gender and weight of patients during intra-dialysis. The length of vector displacement on the Z-graph could show the patient's control of water inter-dialysis, from this, which could be proposed to clinic workers to promote the self-management of the patient. We can help patients to manage their hydrations and diet at home with the graphic method of bioimpedance vector analysis.