Assessment of dry weight in hemodialysis: an overview.

Fluid balance is an integral component of hemodialysis treatments to prevent under- or overhydration, both of which have been demonstrated to have significant effects on intradialytic morbidity and long-term cardiovascular complications. Fluid removal is usually achieved by ultrafiltration to achieve a clinically derived value for "dry weight." Unfortunately, there is no standard measure of dry weight and as a consequence it is difficult to ascertain adequacy of fluid removal for an individual patient. Additionally, there is a lack of information on the effect of ultrafiltration on fluid shifts in the extracellular and intracellular fluid spaces. It is evident that a better understanding of both interdialytic fluid status and fluid changes during hemodialysis is required to develop a precise measure of fluid balance. This article describes the current status of dry weight estimation and reviews emerging techniques for evaluation of fluid shifts. Additionally, it explores the need for a marker of adequacy for fluid removal.