Determination of Extra- and Intraperitoneal Fluid During Peritoneal Dialysis Using Bioimpedance

In peritoneal dialysis (PD), ultrafiltration (UF) failure is commonly attributed to dysfunction of the peritoneal membrane, resulting in decreased ultrafiltration volume (UFV). Our objective was to evaluate whether fluid absorption and UF can be assessed by monitoring intraperitoneal fluid using segmental bioimpedance analysis (sBIA).

Twenty PD patients were studied during either a peritoneal equilibration test (PET; n = 7) or automated PD (APD; n = 13). Eight electrodes were positioned on the lower abdomen and connected to a bioimpedance device (Hydra 4200). A physical model of abdominal extracellular volume (V_ABD) was introduced, consisting of the fluid in extraperitoneal (V_EPF) and the intraperitoneal cavity (V_IPF). The change in the fluid surrounding the peritoneal cavity (ΔV_EPF) was determined by assessing the difference in V_EPF before and after PD. ΔV_Dwell was calculated as the difference between V_ABD at the end and the start of the dialysate dwell. The rate of ΔV_Dwell change due to UF or absorption can be estimated from V_ABD profiles. Total fluid (V_{IPF, D}) in the peritoneal cavity was calculated which was used to compare actual drain volume (V_Drain).

V_Drain and V_{IPF, D} exhibited a strong correlation (PET: R²=0.98, p<0.0001; APD: R²=0.94, p<0.0001). Stable ΔV_EPF (ΔV_EPF=0) was linked to rapid glucose transport, as measured by standard PET.

This study presents a new model utilizing a bioimpedance method to monitor fluid volume across the peritoneal membrane. While the limitation of peritoneal residual volume remains unknown, this approach holds promise for providing a direct measurement of fluid transport during PD.