Bioimpedance Analysis in Dialysis: State of the Art and What We Can Expect

Abstract

Dialysis must control the body’s fluid content accurately in order to maintain optimal health. The only commonly used, practical and objective measurements we have to guide fluid removal are very inaccurate. Recent study has validated bioimpedance (BIA) as an objective measure of fluid and nutritional status in dialysis patients. There are a number of different methods suitable for routine use available to the clinician. Single-frequency whole-body BIA uses inexpensive equipment capable of almost instantaneous or continuous measurement. The results can be used to give an indication of a patient’s fluid content, nutrition and body composition when compared to appropriate reference values. Multiple-frequency whole-body BIA can be used to calculate excess fluid volume to within 1–2 liters. The equipment is more expensive than for single-frequency BIA, but the output is much easier to interpret. Multiple-frequency segmental BIA is more complicated to perform, but subject to less interference from changes in fluid distribution (e.g. resulting from hemodialysis or changes in posture). It is not suitable for routine use but could be considered as a gold standard for occasional clinical BIA.