A blood protein monitor for the continuous measurement of blood volume changes during hemodialysis

Abstract

Hemodialysis treatment comprises the removal of at times considerable amounts of fluid from the circulating blood volume of over-hydrated patients. Subsequently, there is movement of fluid from the interstitial tissue and the intracellular compartment into the vascular bed. While the net fluid removal from the patient is accurately assessed by most dialysis machines, the extent and rate of blood volume reduction cannot be monitored yet. Within the last years, blood volume monitoring has gained increased interest since hypotension, one of the major and most frequent complications of hemodialysis, is believed to be related to the variable tolerance of patients to blood volume reduction. There have been several suggestions for monitoring blood volume changes during hemodialysis. All methods operate on the continuous measurement of an intrinsic property of blood, such as mass density [1, 2], optical density [3], viscosity [4], electrical conductivity [5] or hemoglobin concentration [6]. However, some of these methods proved to have major drawbacks when it comes to the application in clinical practice. Recently, we have developed a sound speed sensor which allows continuous measurement of protein concentration of whole blood [7]. The purpose of our report is the introduction of a new type of sensor which is designed for the routine application of monitoring blood volume changes during hemodialysis treatment.