A fresh look at dry weight

Abstract

The concept of dry weight (DW) is central to dialysis therapy. The most commonly used definition of DW is the weight below which patients become hypotensive on dialysis. However, this definition is dependent on patient symptoms. A more rigorous definition of DW is the body weight at a physiological extracellular volume (ECV) state. Overhydration is an excess in ECV above that found in healthy subjects. In healthy subjects, within extremes of salt intake, ECV may vary between 280 and 340 mL/kg lean body mass. Sodium accumulation is one of the many consequences of renal failure; it results in increased water intake and an increase in ECV, and an accompanying rise in blood pressure with its clinical sequelae, most prominently cardiovascular and cerebrovascular diseases. Recently characterized endogenous digitalis-like factors which are released in response to ECV expansion have extended this traditional picture. Efforts to reduce a positive sodium balance include dietary counseling and avoidance of iatrogenic intradialytic sodium loading, such as dialysate sodium exceeding serum levels, sodium profiling, and intravenous saline. Excess ECV is predominantly located in the interstitial compartment and must be removed during dialysis therapy by ultrafiltration. During this process, interstitial fluid redistributes to the intravascular space via uptake in the capillary bed. In addition to that mechanism, we propose that increased lymphatic flow into the venous system contributes to plasma refilling. Both clinical and technical means are used to assess the presence of DW. Continuous segmental calf bioimpedance is a promising new technology for intradialytic DW diagnosis.

Improving Volume Status by Comprehensive Dietary and Dialytic Sodium Management in Chronic Hemodialysis Patients

“…However, a positive sodium gradient, i.e., the dialysate sodium concentration exceeds the plasma sodium, substantially contributes to a positive sodium balance during treatment by diffusive transport. In addition, inappropriate sodium profiling and excessive saline infusions to treat intradialytic symptoms or as part of dialyzer rinsing and priming procedures may result in sodium loading [18] .…”

Effects of Beta-Blocker Use on Volume Status in Hemodialysis Patients

“…In this study, ECW/BW was chosen as an index of volume status, and can be measured non-invasively using multi-frequency electrical BIA, which is an established method to assess volume status; its utility and validity in dialysis patients have been demonstrated [8,17]. …”

Non Invasive Evaluation of Cardiac Hemodynamics in End Stage Renal Disease (ESRD)

“…Volume overload and target dehydration weight are still largerly estimated empirically [5], even if different methods have been proposed, from biompendance to temperature monitoring and echocardiography evaluations [6]. The latter represent an appealing option, as a relatively cheap, completely harmless method able to describe not only volume status [7][8][9][10] but to picture the spectrum of ESRD cardiomiopathy as well [11][12].…”