Advances in volume monitoring in dialysis patients

Estimating volume status in patients on chronic dialysis is of great clinical value. Both hypervolemia and hypovolemia are associated with serious short term and long term complications, and volume status is often difficult to assess due to multiple factors affecting intravascular and extravascular volume compartments, as well as variability between patients in baseline blood pressures and physical exams. Traditional methods such as estimated dry weight (EDW) and physical exams are often not accurate because of the subjective nature of these indicators and variability between patients' baselines. This can lead to inaccurate volume status estimation and the associated complications. Furthermore, the concept of estimated dry weight is often defined based on measurements of blood pressure which may not accurately reflect volume status. In this review we describe several methods of measuring volume status in dialysis patients that may be more accurate than traditional measurements of blood pressure and dry weight estimation. These methods include dilutional techniques, imaging of vascular structures, use of biomarkers, bioimpedance analysis and online monitoring of biochemical variables during dialysis itself. We also discuss the clinical applicability and comparisons between these methods including the benefits and drawbacks of these methods and areas for future research.