Local tissue bioimpedance measurement for fluid shifts during haemodialysis

Abstract

Haemodialysis has been considered an effective therapy for patients with end-state renal disease; however patients can suffer from adverse side effects during haemodialysis, which are related to the excess shift of fluids between the extracellular and intracellular spaces, as shown in several publications. In this work we used a multifrequency bioimpedance sensor that allows us to determine the fluid volumes and their variations during haemodialysis. Clinical measurements were done with 10 patients (7F, 3M) during 60 HD sessions. Impedance data were recorded on local tissues and for each patient; three impedance sensors were attached to the arm, abdomen, and leg. Bioimpedance data, arterial blood pressure, blood volume and blood haematocrit variations were recorded continuously during the HD sessions. Estimators for the ECW, ICW and TTW volumes and ratios were developed and monitored during the HD sessions. ECW and TTW volumes and the ratios ECW/TTV ECW/TTW showed a clear decrease in response to ultrafiltration. However the behaviour of ICW volume variation was not the same in all patients. The ratios ICW/TTV and ICW/TTW showed an increase between the pre and post-HD states, which indicate that water is removed more from the extracellular space. The validation of our results and the local tissue measurement method was made by calculating the correlations between our fluid estimators and independent sources of information of fluid changes during haemodialysis. © Springer-Verlag 2007.