Monitoring fluid shifts during haemodialysis using local tissue bioimpedance measurement

Abstract

About 25% of patients experience haemodynamic instability during the treatment sessions. These instabilities are related to the excess shift of fluids between the extracellular- ECW- and intracellular- ICW- as shown in several publications during the past 10 years. In this work we developed a multi-frequency 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 heamatocrit 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 during HD in all patients. The ratios ICW/TTV and ICW/TTW showed an increase between the pre and post-HD states which indicates that water is removed more from the extracellular space during ultrafiltration. The validation of our results was made by calculating the correlations between our developed fluid estimators and independent sources of information of fluid changes during heamodialysis. © 2009 Springer Berlin Heidelberg.