Professor Helmut Mann/RWTH Aachen/Germany has earlier done bioimpedance studies in hemodialysis patients. However, I am not aware if he had data regarding intracellular volume changes during hemodialysis. Recenty, Moeller has done bioimpedance studies regarding volume changes during donor plasmaphereses.

"I. Assessment of Fluid Status. This is based primarily on clinical examination, which gives at best a crude estimation. The target body weight or "dry weight" for PD is that weight which gives a well-tolerated normotensive, edema-free state, and, just as in hemodialysis, it is determind by trial and error."

"Bioimpedance analysis...is being used clinically in some (dialysis) centers but without high-grade evidence to justify it (John, 2010)."

Boudville N, Blake PG. Volume Status and Fluid Overload in Peritoneal Dialysis. Ch26 in Daugirdas JT, Blake PG, Ing TS. (Hrsg.) Handbook of Dialysis. Wolters Kluwer 5th ed.; 2015: 483

Thanks for your continued attention. I appreciate your inputs. I am aware of the extensive use of bioimpedance in dialysis treatment and mainly consider our application as a research tool. The ability of monitoring segmental intracellular, interstitial and intravascular volumes and also blood flows and hemodynamic state seems to be useful in looking at volume control during dialysis and a number of other conditions.  For example the we can assess the differential affects of infusion of saline vs Hespan which should be useful in the OR and/or ER. I would like to hear from anyone who has used bioimpedance spectroscopy during dialysis as to the values of Ri during treatment.

again thanks

les montgomery

Please explain the abbreviations OR, ER, and Ri.

OR=operating room. We have used our instrument on the calf during brain surgery and the compartment volumes have tracked the fluid input/output from the patient rather well.

ER=emergency room. we can monitor the changes in intravascular/interstitial fluid during administration of infused fluids (saline goes straight into both vascular and interstitial compartments. Hespan initially only alters intravascular volume then later flows into interstitial).

Ri = resistance from bioimpedance spectroscope that is attributed intracellular tissue. Most commercial spectroscopic units provide Ri (intracellular resistance) and Re (extracellular resistance) only. We then deconvolute the Re to provide measures of interstitial and intravascular volumes and the transfer of fluid between the three compartments.

We temporarily pause the spectroscopic mode at desired intervals and input a 50KHz signal through the segment and record the pulsatile waveforms at 200 Hz. We use these recordings to calculate blood flow and several (34) other parameters regarding pulse transit time, venous tone, arterial tone and contractility.

We have several papers submitted or in preparation regarding these points.

In asking if anyone has data or Ri during dialysis - I am hoping to find anyone with continuous recordings during dialysis to see the extent?? of fluid uptake by the cells. If Ri decreases it is a sign of cell hydration that is independent of our 3 compartment calculations.

I hope this helps.

les montgomery

What are the inputs and expected outputs for bioimpedance measurement?