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There are two distinct facets of adequate fluid balance control in haemodialysis patients--estimation of dry weight (DW) as the target and adequate ultrafiltration (UF) strategy, i.e. the way to reach the target in a possibly symptom-free way. The article reviews the continuous blood volume monitoring (CBVM) based procedures to deal with the former facet-DW determination. The existing approaches are divided in three groups--methods defining certain alert value of relative blood volume (RBV) reduction, methods working with RBV response to constant UF rate, and methods evaluating dynamics of RBV response to UF pulse or chain of UF pulses. While the first and the third approaches are relatively easy to automate, the second group of methods are suitable mainly for observational evaluations only. All the discussed methods, without exception, need large-scale verification, as they all were evaluated in the majority by their authors only and on small patient cohorts.

This article reviews vascular access (VA) assessment methods and procedures. It gives an overview of the existing methods for bed-side VA assessment by means of pressures, recirculation and access flow measurement. Pros and cons of the methods are discussed and additional benefits of a combined recirculation and access flow measurement are explained. Present vascular access care guidelines are discussed, namely the K/DOQI and EVAS documents. Practical setup of a vascular access monitoring and surveillance system is illustrated with data from the authors' own unit where such a system has been in use since 1999. The issue of adequate target setting is analysed in view of published works on clinical impact of access surveillance system introduction (timely detection of access stenosis and access patency). Critical re-evaluation is needed especially in current QVA threshold and intervention timing.

The article discusses the issue of suitable parameters (pressures, recirculation and access flow) to assess hemodialysis vascular access quality (VAQ), available methods to measure those parameters and the setup of the entire VAQ surveillance system (VAQS) in a dialysis facility. Special attention is paid to factors which need some standardization to enable evaluation of VAQ trends in an individual as well as comparison of data from different patients and different dialysis facilities. The discussed procedures are documented with the authors' own measurement results and the results of the VAQS implemented in their unit. Both dynamic and static pressures exhibit insufficient sensitivity in detecting stenoses in native arteriovenous fistulas. Access recirculation is a late finding because with its non-zero value dialysis quality is already compromised. Timely and reliable detection of a deteriorating access condition is enabled by access flow (QVA) only. No standardization is needed in extracorporeal blood flow used in QVA evaluation by ultrasonic dilution. Multiple measurements may increase the reliability of thermodilutional measurements and are a must in optodilutional ones. Timing of the measurement during dialysis should be standardized. Measurement frequency should take into account access type, QVA value and access history. Shortened intervals are needed in the immediate post-intervention period with regard to risk of re-stenosis incidence and strongly nonlinear QVA decreases in such cases. A significant shift-over from surgical interventions to balloon angioplasties is to be expected with the introduction of a VAQS, and appropriate measures must be taken to ensure their quick availability., (Copyright 2005 S. Karger AG, Basel.)

In order to deliver a specific dialysis dose (Kt/V) to all patients, their product Kt (urea clearance K multiplied by dialysis time t) should be individually adjusted according to total body water (V) of each patient. With dialysis time being fixed in most centres for organisational reasons, such individualization can be accomplished by individually set blood flow (QB). For a given t, the value of QB also defines the magnitude of the cumulative blood volume (VB = QB*t), i.e. the volume of blood perfused through the dialyser during the whole dialysis time. VB is displayed by every contemporary dialysis machine but not used. The aim of this work was to derive an easy to use approach to QB individualization based on patient's body weight and dialysis time to obtain a desired Kt/V value which would also be easy to check after dialysis by looking at the obtained VB value. Statistically significant correlation was found between the QB-based Kt/V estimation and Kt/V determined by the other two methods demonstrating practical feasibility of the novel approach. Kt/V values obtained with the QB prescribed according to patient's body weight tended to be better in females and patients with higher body mass index.

Access dysfunction presents a risk for haemodialysis patients and is costly for health care providers. Regular vascular access quality (VAQ) monitoring enables the detection of adverse access conditions early allowing timely interventions, which will presumably be less invasive, more successful and cheaper. This paper reviews all currently used assessment parameters: dynamic and static pressures, recirculation and blood flow through the access--and analyses pros and cons of each of them. Based on this overview it is concluded that access flow monitoring should be the method of choice, possibly combined with monitoring of another parameter to further enlarge diagnostic possibilities of the monitoring. The VAQ monitoring system developed and used currently in the author's dialysis centre is briefly described as an example. The issue of access flow related to haemodynamics is briefly mentioned. With the introduction of any VAQ monitoring system, one has to acknowledge a change in structure of interventions and that the demand for surgical procedures decreases with a concurrent increase in percutaneous interventions.

Our department has been using continuous blood volume monitoring (Critline instrument, In-line Diagnostics, Riverdale, USA) for over two years now. First during research on sodium concentration control in haemodialysis (HD), later in the project on assessment and control of hydration in HD patients.