Assessment of post-dialysis dry weight: an application of the conductivity measurement method.

Abstract

In the clinical practice of hemodialysis, estimation of is a major problem. Dry is defined as that weight at the end of a dialysis treatment below which the patient, more often than not, will develop symptoms of hypotension [1]. Overestimation of dry weight will expose the patient to the potential hazards of overhydration, such as hypertension and pulmonary edema. On the other hand, underestimation of dry weight will make the patient more prone to suffer from hypotensive episodes during dialysis. In the absence of overt clinical signs of dehydration or overhydration, blood pressure is often used as an index of correct hydration. However, it is well known that such a clinical parameter is insensitive in detecting abnormalities of the fluid balance in dialysis patients [2]. Therefore, new techniques to assess dry weight are warranted [3–5]. In previous reports we have shown that changes in regional tissue hydration can be detected by non-invasive conductivity measurements [6, 7]. The technique separately detects intra (IFV)- and extracellular fluid volume (EFV). In a steady state condition IFV and EFV calculated according to this method showed an excellent correlation with IFV and EFV determined by conventional isotopic dilution techniques [8]. In the present study pre- and post-dialysis values of IFV and EFV were compared to normal values obtained from measurements in healthy volunteers in order to identify post-dialysis over- and underhydration. Secondly, the effect of fluid withdrawal on blood volume (BV), EFV, IFV and hemodynamics in over- and underhydrated patients was investigated.