Relative blood volume changes during haemodialysis estimated from haemoconcentration markers

L Pstras,W Zaluska,A Wojcik-Zaluska,J Waniewski

doi:10.1038/s41598-020-71830-0

Abstract

Relative blood volume (RBV) monitoring is frequently used in haemodialysis patients to help guide fluid management and improve cardiovascular stability. RBV changes are typically estimated based on online measurements of certain haemoconcentration markers, such as haematocrit (HCT), haemoglobin (HGB) or total blood protein concentration (TBP). The beginning of a haemodialysis procedure, i.e. filling the extracorporeal circuit with the patient’s blood (with the priming saline being infused to the patient or discarded) may be associated with relatively dynamic changes in the circulation, and hence the observed RBV changes may depend on the exact moment of starting the measurements. The aim of this study was to use a mathematical model to assess this issue quantitatively. The model-based simulations indicate that when the priming saline is not discarded but infused to the patient, a few-minute difference in the moment of starting RBV tracking through measurements of HCT, HGB or TBP may substantially affect the RBV changes observed throughout the dialysis session, especially with large priming volumes. A possible overestimation of the actual RBV changes is the highest when the measurements are started within a couple of minutes after the infusion of priming saline is completed.

Highlights

Relative blood volume (RBV) monitoring is frequently used in haemodialysis patients to help guide fluid management and improve cardiovascular stability
Given that it is not feasible to continuously or frequently measure the actual total blood volume during HD, in clinical settings the relative blood volume (RBV) changes are assessed based on changes in certain blood parameters, such as haematocrit (HCT), haemoglobin (HGB) or total blood protein concentration (TBP), which can be estimated from non-invasive measurements of optical, acoustic or other properties of blood flowing through the dialysis c ircuit[10,11]
The RBV changes during the HD procedure simulated by the model and estimated from different blood parameters—HCT, HGB or TBP—measured in the virtual arterial blood line compartment are shown in Fig. 3 with four different starting points of measurements: (a) at the beginning of the whole HD procedure, i.e. at the start of filling the extracorporeal circuit with the patient’s blood; (b) at the end of filling the extracorporeal circuit with the patient’s blood; (c) at the start of the actual HD; (d) 5 min into haemodialysis session

Summary

Introduction

Relative blood volume (RBV) monitoring is frequently used in haemodialysis patients to help guide fluid management and improve cardiovascular stability. The model-based simulations indicate that when the priming saline is not discarded but infused to the patient, a few-minute difference in the moment of starting RBV tracking through measurements of HCT, HGB or TBP may substantially affect the RBV changes observed throughout the dialysis session, especially with large priming volumes. Given that it is not feasible to continuously or frequently measure the actual total blood volume during HD, in clinical settings the relative blood volume (RBV) changes are assessed based on changes in certain blood parameters, such as haematocrit (HCT), haemoglobin (HGB) or total blood protein concentration (TBP), which can be estimated from non-invasive measurements of optical, acoustic or other properties of blood flowing through the dialysis c ircuit[10,11]. Where at any time point t, the current level of haematocrit (HCTt) is compared to the initial reference haematocrit (HCT0)

Objectives

Methods

Results

Conclusion