A new technique for establishing dry weight in hemodialysis patients via whole body bioimpedance

Background. Quantitative techniques are necessary to achieve dry weight (DW) in patients with kidney failure. Bioimpedance spectroscopy (BIS) is a non-invasive method that determines the volume of body fluid compartments. The current work evaluates the use of BIS data in hemodialysis patients for the prediction of DW. Methods. A new technique has been devised for the estimation of DW that involves the intersection of two slopes, slope normovolemia (S-NV ) and slope hypervolemia (S-HV ). These slopes characterize the variation in extracellular water (ECW) with body weight (BW) in the states of normovolemia and hypervolemia, respectively. S-NV was established via measurements of ECW and BW in 30 healthy subjects. In a longitudinal study in new hemodialysis patients, successive reduction of post-dialysis weight (PDW) was attempted until clinical signs of normovolemia were presented. Measurements of ECW and BW that were acquired at the beginning of each treatment were used to determine S-HV . Results. S-NV was found to be 0.239 L/kg and 0.214 L/kg for male and female healthy subjects, respectively. A significant DeltaPDW predicted by the new method (-4.98 kg) was highly correlated to the DeltaPDW achieved in the study (-5.85 kg, R = 0.839). Blood pressure was reduced (P < 0.001) and an 86% decrease in antihypertensive agents was achieved. Conclusion. The method of intersecting slopes (S-HV with S-NV ) via BIS is a new method for the prediction DW. This approach will offer considerable improvement for the routine management of DW in the dialysis setting.