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Methods: Records of 10,000 QVA measurement performed in 549 patients over 20 years were used as retrospective and anonymized data source, making ethical commission involvement unnecessary. Two approaches are used to elucidate association of QVA changes with different factors: analyses of smaller cohorts in which both the QVA and the respective factor were measured (e.g. association of QVA with cardiac output (CO)), or-in case of rare phenomena-a form of a well illustrated case reports was used (e.g. association of QVA and Kt/V)., Results: Significant increase in CO after permanent VA creation (3-4-fold of the QVA value) was found. Impact of intradialytic CO changes on QVA is attenuated by relatively stable VA resistance compared to systemic resistance. Blood pressure impact is much stronger and it should therefore be noted at each QVA measurement. As reproducibility of different QVA measurement methods varies, use of the same method should be preferred. Direction of the arterial needle insertion in VA affects the QVA measured, especially in synthetic grafts, too. Also patient's own QVA variability may be quite high. All this makes KDOQI/EBPG recommended acceptable QVA drops too strict, they should be revised. In re-stenoses prone patients, measurement intervals should be shortened, too., Conclusion: QVA values are significantly affected by many factors. Their knowledge appears essential for safe and effective VA surveillance and management.

Measurement of living tissue impedance - bioimpedometry - started to be used in medicine some 50 years ago, first exclusively for estimation of extracellular and intracellular compartment volumes. Its most simple single frequency (50 kHz) version works directly with the measured impedance vector. Technically more sophisticated versions convert the measured impedance in values of volumes of different compartments of body fluids and calculate also principal markers of nutritional status (lean body mass, adipose tissue mass). The latest version specifically developed for application in dialysis patients includes body composition modelling and provides even absolute value of overhydration (excess fluid). Still in experimental phase is the bioimpedance exploitation for more precise estimation of residual glomerular filtration. Not yet standardized is also segmental bioimpedance measurement which should enable separate assessment of hydration status of the trunk segment and ultrafiltration capacity of peritoneum in peritoneal dialysis patients.Key words: assessment - bioimpedance - excess fluid - fluid status - glomerular filtration - haemodialysis - nutritional status - peritoneal dialysis.

Phosphorus removal by hemoelimination procedure is a important mechanism to maintain phosphorus level in acceptable level in patients on dialysis. Phosphorus is removed by both diffusion and convection, but in clinical practice, it is not possible to differentiate the contribution of this two transport modalities. We used Gutzwiller formula to quantify the amount of removed phosphorus and compared it in low-flux hemodialysis (LFHD), high-flux hemodialysis (HFHD), and on-line hemodiafiltration (HDF). There were no significant differences in phosphorus predialysis concentration, duration of procedure, processed blood volume and ultrafiltration, e.g., factors, which could possibly influence phosphorus elimination. All three tested dialysis modes also did not differ in urea dialysis dose (Kt/V) as a parameter of small molecular weight removal (LFHD, 1.50 ± 0.04 vs HFHD, 1.5 ± 0.06 vs HDF, 1.5 ± 0.05). The amount of removed phosphorus in LFHD, HFHD, and HDF was 34.0 ± 1.2, 37.8 ± 1.6, and 38.3 ± 1.4 mmol, respectively. Statistically significant increase in phosphorus removal was seen only with use of high-flux membrane (HFHD and HDF) when compared with the low-flux one. No difference was, however, found between HFHD and HDF. It can thus be concluded that phosphorus removal in all three dialysis modes is a predominantly diffusive issue and contribution of convection to it is minor to negligible.

Central venous catheter (CVC)-related problems, risks and safety hazards are partly caused by different characteristics of the CVC-based access and their performance features. This chapter covers those issues in a chronological order, from factors related to the choice of the CVC, insertion site and insertion procedure itself, over those associated with CVC use and their monitoring up to safety hazards of interventional procedures. Not discussed are CVC infections as they are covered in a separate chapter in this book., (© 2015 S. Karger AG, Basel.)

The aim of this study was to investigate an association between vascular access blood flow (QVA), cardiac output(CO), and load of left ventricle (LLV) using a simple physical model calculation based on real data, specifically inpatients with high access blood flow arteriovenous fistula(AVF). Vascular access blood flow, CO, and peripheral vascular resistance (PR) were determined by ultrasound dilution technique (HD01; Transonic Systems, Inc., Ithaca, NY). Load of left ventricle was calculated using simplified formula: LLV x PR CO2. This total load was computationally divided into the part spent to run the flow QVA through the AVF (LLVAVF) and that part ensuring the flow (CO-QVA) through the vascular system. The model calculation was first performed in a selected group of 15 patients with high access blood flow (QVA >1,300 ml/min, group 1) and later extended for comparison by another group of 40 unselected patients with access blood flow in lower range (QVA range 200-1,400 ml/min, group 2).Mean LLV in group 1 was 2.10 +/- 0.68 W. LLV(AVF) was 21.8% of total LLV. Mean LLV in group 2 was 1.2 +/- 0.5 W.LLVAVF was 11.1% of total LLV. Our computational results suggest that AVF in typical range of QVA shall not increase heart load significantly.

Background: Intradialytic morbid events (IMEs) during haemodialysis (HD), including symptomatic hypotension, are related to ultrafiltration (UF)-induced hypovolaemia. Blood volume monitoring and automatic feedback control of the UF rate were developed to limit the extent of hypovolaemia during dialysis. The present study investigated the effect of blood volume (BV)-controlled UF on the incidence of HD treatments with IMEs., Methods: This prospective randomised crossover study included hypotension-prone patients, characterised by occurrence of IMEs in at least 33% of HD treatments during a 6-week screening phase. These patients underwent 2 treatment phases, each lasting 6 weeks, in randomised order. Each patient served as their own control, treated with standard HD in one phase and with BV-controlled UF in the other phase., Results: Thirty-four patients from 9 HD centres were enrolled; 26 could be included in the analysis population. In comparison with standard HD, BV-controlled UF reduced the percentage of HD sessions complicated by IME significantly from 40%+/-27% to 32%+/-25% (p=0.02). A lower frequency of HD sessions with IME could be observed in 46% of the patients. The frequency of treatments with symptomatic hypotension was reduced from 32%+/-23% in standard HD to 24%+/-21% with BV-controlled UF (p=0.04). Changes in blood pressure and heart rate from start to end of the HD session were not different between the 2 treatment modes., Conclusions: This crossover study showed improved intradialytic stability with BV-controlled UF, compared with standard HD.

Terahertz (THz) time-domain spectroscopy was used in vivo to measure the body reflectance with the aim of determining experimentally the influence of haemodialysis on the content of water in the human skin. For this purpose, an original methodology of determining the skin properties at THz frequencies from the reflectance was developed. A series of measurements were performed before and after dialysis with ten subjects. The results strongly indicate that the surface body hydration is not the main parameter determining the skin conductivity in the THz range.

Aim: To assess the variability of blood flow (QVA) through a native arteriovenous fistula (AVF) in the long-term and to determine the QVA reduction at which an intervention is appropriate., Patients and Methods: The study was performed in a group of 34 chronic hemodialysis patients with no history of a AVF intervention. QVA was measured using the thermodilution method (Blood Thermodilution Monitor, Fresenius). Median follow-up was 41 months and the median number of QVA measurements in each patient was 15. The coefficient of variation (CV) of QVA was calculated for each patient., Results: Mean QVA was 904 +/- 334 ml/min. The mean CV was 23.3 +/- 11.2%., Conclusion: QVA may fluctuate during a long-term follow-up period. The detection of QVA decrease by 20-25% could be still within physiological limits. Based on the results we recommend to first repeat the measurement at a shorter interval and to refer the patient to a radiologist only when the decreasing trend is confirmed., (Copyright 2008 S. Karger AG, Basel.)

Background: During routine haemodialysis (HD) body temperature increases, which contributes to haemodynamic instability. The relative roles of increased heat production and/or incomplete heat transfer are not fully elucidated. Concomitant measurement of heat production and heat transfer may help to assess the factors determining thermal balance during HD., Methods: Thirteen stable non-diabetic maintenance HD patients were investigated during two HD procedures (isothermic, dT = 0, no change of body temperature; thermoneutral, dE = 0, no energy transfer between blood and dialysate), using a blood temperature monitor (BTM) in active mode. Energy transfer, blood and dialysate temperature, and relative blood volume change (dBV) were continuously recorded, and resting energy expenditure (REE; Deltatrac Datex) was measured repeatedly during each procedure. Fourteen healthy persons served as controls for REE comparison., Results: In isothermic HD, median energy removal was 218 kJ/4 h HD (= heat flow -15.1 W). This cooling correlated with dBV induced by ultrafiltration (rho = 0.731, P < 0.01). There was no difference in dBV between isothermic (7.7%) and thermoneutral (8.1%) HD. Predialysis REE was 82.8 W/1.73 m(2), not different from controls. No variation in REE during HD was observed, except a small and transient increase after a light meal (5 and 4%). In the time course of REE, no difference between the procedures was found., Conclusions: Our findings suggest that stable maintenance HD patients have REE not different from healthy controls, that HD procedure per se does not significantly increase REE and that neither isothermic nor thermoneutral regimen has any influence on metabolic rate. Therefore, body temperature elevation during routine HD may rather be due to decreased heat removal. With the use of BTM in active mode, body temperature can be kept stable (isothermic HD), which requires active cooling. This negative energy transfer is proportional to decrease in blood volume induced by ultrafiltration.

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.

Existing national, racial, and ethnic differences in dialysis patient mortality rates largely are unexplained. This study aimed to test the hypothesis that mortality rates related to atherosclerotic cardiovascular disease (ASCVD) in dialysis populations (DP) and in the background general populations (GP) are correlated. In a cross-sectional, multinational study, all-cause and ASCVD mortality rates were compared between GP and DP using the most recent data from the World Health Organization mortality database (67 countries; 1,571,852,000 population) and from national renal registries (26 countries; 623,900 population). Across GP of 67 countries (14,082,146 deaths), all-cause mortality rates (median 8.88 per 1000 population; range 1.93 to 15.40) were strongly related to ASCVD mortality rates (median 3.21; range 0.53 to 8.69), with Eastern European countries clustering in the upper and Southeast and East Asian countries in the lower rate ranges. Across DP (103,432 deaths), mortality rates from all causes (median 166.20; range 54.47 to 268.80) and from ASCVD (median 63.39 per 1000 population; range 21.52 to 162.40) were higher and strongly correlated. ASCVD mortality rates in DP and in the GP were significantly correlated; the relationship became even stronger after adjustment for age (R(2) = 0.56, P < 0.0001). A substantial portion of the variability in mortality rates that were observed across DP worldwide is attributable to the variability in background ASCVD mortality rates in the respective GP. Genetic and environmental factors may underlie these differences.

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.

Very few studies have so far reported about resting energy expenditure (REE) in chronic renal failure and there is no information available on REE during hemodialysis (HD). Hypothetically, we can expect an increase in REE during HD procedure (due to the inflammatory response to extracorporeal blood circuit). However, such increase in REE could be modified by thermal balance of the procedure. In our study, REE was measured by indirect calorimetry (Deltatrac Datex) in a group of 13 HD patients (7 males and 6 females, mean age 59.8 +/- 13.5 years). In each patient, REE was assessed during two HD sessions: one isothermic and one thermoneutral. All other HD parameters were kept constant. The control group consisted of 14 healthy subjects (4 males and 10 females, mean age 41.3 +/- 20.5 years) with normal renal function. There was a significant difference in thermal balance between the two HD settings: -199 kJ/HD in isothermic and -4kJ/HD in thermoneutral HD sessions (p < 0.01). Measured REE values obtained in HD patients before HD session (7 316 +/- 919 kJ/day/1.73 m2) did not differ significantly from those of the healthy controls (7 264 +/- 1 016 kJ/day/1.73 m2). Similarly, there was no significant difference in calculated EE values (Harris-Benedict equation). In the 10th minute of the HD session, there was a slight, transitory decrease in REE (mean decrease by 3.2% during isothermic and by 2.8% during thermoneutral HD session, ns). In the 70th minute, REE returned to pre-dialysis values. After a light meal in the 110th minute REE increased by 8% during isothermic and by 6.3% during thermoneutral HD session. At the end of the HD session (i.e. in the 215th minute) REE again returned to pre-dialysis values. Intra-dialysis changes in REE were similar in both isothermic and thermoneutral HD sessions. The results of our study did not confirm the expected influence of HD procedure on REE in the two different thermal HD settings. We conclude that there is no significant difference between REE in HD patients and healthy controls and that REE values are not significantly influenced by hemodialysis procedure.

Dynamic arterial and venous pressures (PA, PV) are used as the simplest tools to assess vascular access quality (VAQ). An increased PV over three consecutive dialyses is believed to indicate a stenosis, a rule devised for synthetic grafts (AVG) but not adequately validated for AV fistulas (AVF). In this study dynamic PV and static intra-access pressure (calculated by means of the simplified formula PIA=(PA+PV)/2) changes were evaluated in 46 accesses in which balloon angioplasty had to eventually be performed. The whole group consisted of 30 forearm AVF, 5 upper arm AVF and 11 AVG. Pressures were compared in each patient at a time of satisfactory access flow (QVA) and immediately before the angioplasty and pressure difference over that period (deltaPV, deltaPIA) evaluated. Despite a significant drop in QVA over the follow-up interval in both AVF and AVG, the mean deltaPV and deltaPIA in AVF were only several mm Hg and the chosen threshold limit of 20 mmHg was exceeded in approximately 10% of patients only. The results in the AVG group were, however, very different: The mean deltaPV and deltaPIA were close to 20 mmHg and almost 60% of patients in the AVG group exceeded this limit. Evaluation of PIA did not improve stenosis detection in either group. It is concluded that PV and/or PIA monitoring may be useful to detect a stenosis in AVG but not in AVF.

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.)

The EDTNA/ERCA European Practice Database (EPD) Project has been launched with the aim to collect data on professional practice and outcome of dialysis treatment throughout Europe. The Czech Republic had the privilege of taking part in the pilot phase together with Northern England and part of Italy. We first became involved in the EPD project during the annual EDTNA/ERCA conference in Nice, France. At this time the Research Board started to prepare an EPD questionnaire for the pilot phase. The project was officially launched in the Czech Republic during the Multidisciplinary Conference in Brno organised jointly by the Czech Association of Nurses and the EDTNA/ERCA in 2003. A presentation by Jean Yves De Vos, the EPD Co-ordinator, who introduced the final EPD questionnaire in detail, was the best promotion of the project.

Measurement of vascular access flow (QVA) has been suggested as a method of choice for vascular access quality (VAQ) monitoring. Besides traditional duplex Doppler, a number of bedside methods based mostly on the Krivitski principle of QVA evaluation from recirculation at reversed needles (RX), have been developed. This work compares ultrasonic dilution (UD), taken as a reference, HD01, Transonic Systems; duplex Doppler (DD); thermodilution (TD), BTM, Fresenius; optodilutional RX measurement (ORX), Critline III, R-mode, HemaMetrics; direct optodilutional QVA evaluation from jumpwise changes in ultrafiltration rate at both normal and reversed needles connection (OABF), Critline III, ABF-mode; and direct transcutaneous optodilutional QVA evaluation (TQA), Critline III TQA. Firstly, reproducibility of each method was assessed by duplicate measurement at unchanged conditions. This was followed by paired measurement with each method performed at controlled change in relevant measurement condition (two different extracorporeal blood flows in UD and TD, changed sensor position in TQA). Finally paired measurements by each method and the reference method performed at identical conditions were evaluated to assess accuracy of each method. The simple Krivitski formula QVA=QB(1-RX)/RX was used wherever manual QVA calculation was needed. Very high reproducibility was seen in UD, both for measurement at the same extra corporeal blood flow (QB) (correlation coefficient of duplicate measurement r=0.9702, n=58) and for measurement at two different QB (r=0.9735, n=24), justifying its current status of a reference method in QVA evaluation. Slightly lower reproducibility of TD measurement at the same QB (r=0.9197, n=40) and at two different QB (r=0.8508, n=168) can be easily overcome by duplicate measurement with averaging. High correlation of TD vs. UD (r=0.9543, n=54) makes TD a viable clinical alternative in QVA evaluation. Consistently different QVA obtained at two different QB should prompt closer investigation of anatomical conditions of the access. Use of the simple Krivitski formula in TD (which measures total recirculation, i.e. sum of access recirculation and cardiopulmonary recirculation) brings about underestimation of QVA, which progressively increases from QVA of about 600 mL/min up. Good correlation, although with significant scatter (r=0.8691, n=27) was found between the DD- and UD-based QVA. By far the worst reproducibility at the same QB from among the investigated methods was found in ORX (0.6430, n 23). Also the correlation of ORX vs. UD was lower than in other methods (r=0.702, n=33) and general overestimation of QVA by about 25% was noted. Correlation of OABF vs. UD (r=0.6957, n=26) was slightly better than that of ORX and it gave less overestimated values. The TQA method showed very high reproducibility (r=0.9712, n=85), however only for unchanged sensor position. Correlation of QVA measured at two different sensor positions was much worse (r=0.7255, n=22). Correspondence of TQA vs. UD was satisfactory (r=0.8077, n=36). Skilled and experienced operators are a must with this method.

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.

Vascular access quality monitoring by means of vascular access blood flow (QVA) evaluated from automated thermodilutional measurement of recirculation with reverse needle position is described. This method provides significant advantages over conventional methods based on simple monitoring of pressures in the extracorporeal circuit and/or measurement of recirculation with normal needle position. AQVA evaluation protocol was developed and introduced into the system of primary nursing. The QVA values were found independent of the extracorporeal blood flow used during the recirculation measurement. QVA values from below 200 ml/min to over 2 l/min were seen. In general, lower values were found in diabetics compared to non-diabetics and in females compared to males. While blood flow below 600 ml/min is considered risky for synthetic vascular grafts, native AV-fistulae seem to remain stable and patent at a flow of 400 ml/min or even below. The method is able to detect erroneous needle placement in looped grafts, stenosis between needles, and is also well suited for effective evaluation of success/failure of interventions on access.

The article describes novel method of vascular access quality assessment by means of combined measurement of recirculation with normal and inverse needles placement and calculation of vascular access blood flow from the recirculation data. Blood flow values seen in a large group of patients ranged from as low as 200 ml/min up to as high as 2 l/min. Females and diabetics exhibited lower values as compared to males and non-diabetics. The method enables to detect a number of anomalous sates which cannot be detected by conventional means based on monitoring of pressures or recirculation measurement at normal needles placement only (stenosis between both needles, uintentionally erroneous placement of needles in accesses with a loop). Assessment of access blood flow is suitable also for evaluation of interventions on the access, such as percutaneous transluminal angioplasty or surgical narrowing of anastomosis in case of too high blood flow.

The quality of water used for dialysis is not subject to any mandatory regulations in most European countries. A survey of haemodialysis facilities in 14 countries carried out by the European Dialysis and Transplant Nurses Association/European Renal Care Association (EDTNA/ERCA) showed that the majority of centres aimed to meet the requirements of the European Pharmacopoeia, but only 50% carried out tests to check compliance. The wide variation in policies for maintaining and monitoring the equipment and the distribution system indicates that guidelines for water treatment are urgently needed in Europe.

The recently introduced continuous blood volume monitoring (CBVM) technique enables real time observation of the blood volume (BV) response to ultrafiltration. This response differs quite widely among patients even under otherwise comparable conditions. Assessing the clinical recordings of over 100 CBVM measurements, identification of a static and a dynamic component of the overall BV reduction was made. Computational analysis of the factors that influence BV response variability was then performed by means of a three-pool model of sodium, potassium, and urea kinetics with the following results. The blood volume profile contains clinically highly interesting yet cumulative information. Except for the small change and flat BV profiles the static component is predominant. From the external factors, the static component of BV reduction during hemodialysis is influenced by the total ultrafiltered volume and by the degree of overhydration. From the patient's internal factors, compliance of his cardiovascular system is dominant. BV is also more reduced in patients with lower values of total plasma protein content and/or lower hematocrit. The BV reduction dynamic component is primarily influenced by the applied ultrafiltration rate. A certain influence is also exerted by the ultrafiltration coefficient of the capillary wall which may vary in different individuals.

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.

A continuous blood volume monitoring (CBVM) device (Inline Diagnostics, Riverdale, USA) was used to study response to prescribed ultrafiltration during haemodialysis (HD) in 66 stabilised HD patients. Fifty percent of patients showed the expected linear decrease in BV right from the beginning of HD (group 1), 32% exhibited no decrease at all (group 2), while eighteen percent formed the transient group 3 which showed a plateau of varying length after which a decrease occurred. The correct setting of dry weight was verified through evaluation of the ratio of extracellular fluid volume to total body water (VEC/TBW) in 26 patients by means of whole body multifrequency impedometry MFI (Xitron Tech., San Diego, USA) and through measurement of the Vena Cava Inferior diameter (VCID) pre and post HD (in 6 and 5 patients from groups 1 and 3 and from group 2, respectively). The mean VEC/TBW in groups 1 and 3 was 0.56 pre and 0.51 post HD as compared to 0.583 and 0.551 in group 2. VCID decreased on average by 14.1% in groups 1 and 3 but remained stable in group 2. Both findings thus confirmed inadequately high estimation of dry weight. Since CBVM is extremely easy to perform it can be used as a method of choice in detecting inadequately high prescribed dry weight. The status of the cardiovascular system must always be considered before final judgement is made.

The use of multifrequency bioimpedance (MFB) for determination of dry weight (DW) in haemodialysis (HD) patients was evaluated in three studies. In Study 1, the fluid state [total body water (TBW) and extracellular volume (ECV)] was measured by MFB in 82 normotensive patients. 41 hypertensive patients and in 30 healthy subjects. TBW and ECV were expressed as per cent of body weight (BW). In Study 2, DW of five hypertensive HD patients was gradually decreased during 3 months and ECV (MFB) and blood pressure (48 h ambulatory blood pressure monitoring) were measured at the beginning and end of study. In Study 3, we measured the fluid status repeatedly by MFB and the diameter of the inferior vena cava (DIVC) by ultrasound before, during and 2 h post-HD. In Study 1, the hypertensive patients had significantly greater TBW (P < 0.05) than the normotensive patients before (50.3 +/- 6.5% vs 47.6 +/- 5.8%) and after HD (48.8 +/- 7.8% vs 45.7 +/- 6.4%) and ECV (P < 0.001) before (29.4 +/- 3.6% vs 26.8 +/- 3.5%) and after HD (27.0 +/- 4.0% vs 24.6 +/- 3.5%), Post-HD ECV in the normotensive patients was similar to that in the healthy subjects. In Study 2, more efficient ultrafiltration resulted in reduction of BW and ECV along with a decrease in blood pressure and need for antihypertensive medication. In Study 3, both ECV and DIVC decreased following the removal of fluid during HD. ECV maintained stable values during the post-HD period, unlike DIVC which increased significantly (P < 0.005) due to refilling from the interstitial space. We conclude that MFB is an appropriate non-invasive method for DW determination, which is highly reproducible and technically simple to use.

Whole body impedometry is relatively new non-invasive method to measure the distribution of total body water (TBW) between extra- and intracellular compartment (VEC, VIC). Having applied linear regression analysis onto the relation of the ratio of the extracellular volume to the volume of total body water (VEC/TBW) and the age in a group of healthy individuals very narrow scatter from the regression line was found. This line can thus be used as an indicator of normohydration status with respect to age. Assuming that the relation of VEC/TBW vs. age is the same in dialysed patients and that the state of normohydration corresponds to the so called dry weight, the VEC/TBW value can be used as a novel indicator of dry weight. Any deviation of the pre-dialysis VEC/TBW value from normal could easily be used to establish the desired ultrafiltration and dry weight. With regard to the known inaccuracy with which the dry weight is determined from purely clinical assessment this approach may lead to substantial objectivisation in determination of this principal parameter. It may be especially helpful in case of newly admitted patients. The suggested new approach to dry weight determination is supported by the finding of statistically significant relation between post-dialysis deviation of the VEC/TBW ratio from the normal value vs. blood volume reduction at the end of the dialysis session. Patients classified at the end of a dialysis session as still overhydrated by their VEC/TBW deviation from normal showed little or no reduction in their blood volume. An investigation of the Vena Cava Inferior diameter in a subgroup of these patients confirmed this finding showing no decrease at the end of dialysis. On the contrary, the patients whose post-dialysis VEC/TBW value was normal or below normal showed both significant reduction in their blood volume as well as decrease in the Vena Cava Inferior diameter.

Traditionally Gibbs-Donnan coefficients based on the mean charge of plasma proteins are used as the only correction factor in equations describing sodium transport across the dialyzer membrane. This ignores the possible impact of the membrane material. Correction coefficients (CC) of the whole dialyzer were measured during in vivo dialysis as a quotient of dialysate to plasma sodium in an equilibrated state for different membrane materials used in commercially available dialyzers. Their mean value and correlation with total plasma protein content (TPP) were evaluated. CC for the six materials evaluated differed both in the intercept and slope of the regression line CC versus TPP: Cuprophan 1: CC = 1.0253 - 0.00017 x TPP; Hemophan 1: CC = 1.119 - 0.00175 x TPP; Hemophan 2: CC = 1.095 - 0.00111 x TPP; PMMA: CC = 1.0353 - 0.00044 x TPP; SCE:CC = 1.114 - 0.00145 x TPP; and Cuprophan 1:CC = 1.0562 - 0.00065 x TPP. The observed differences are attributed to the different charge densities of the membrane materials and suggest that for a precise description of sodium transport, the role of the membrane material needs to be considered.

The urea generation rate (G) and the protein catabolic rate (PCR) have been investigated in two groups of hemodialyzed patients over a whole week cycle, one with zero residual renal function (Kr = 0) dialyzed thrice weekly and the other dialyzed twice weekly with nonzero residual renal function. The two-pool model of urea kinetics was used. No relationship between patients' age and the PCR was found, and also no difference in the PCR between males and females was seen. All patients with a PCR < 0.8 g/kg/day had a midweek predialysis plasma urea level well below 25 mmol/L, which clearly documents the value of a kinetic approach in early detection of patients at risk for malnutrition. In the thrice weekly dialyzed group, a statistically significant relationship was found between PCR and KT/V:PCR = 0.582 + 0.253 x KT/V, r = 0.374 with p < 0.05. In the twice weekly dialyzed group with nonzero Kr, contribution of the residual renal function had to be included into KT/V to reach a level of statistical significance of PCR = 0.697 + 0.18 x KT/V, r = 0.481 with p < 0.05. With regard to values of Kr encountered in the investigated group (0-3.5 ml/min), its influence upon PCR is higher than a volumetrically equal increase in excretorial efficacy of the artificial kidney. The G in the thrice weekly dialyzed group was found to be dependent on the length of the interdialytic interval over which it was evaluated. Over the intervals Friday-Monday, Monday-Wednesday, and Wednesday-Friday the following mean values of G were obtained: 0.155, 0.180, and 0.188 mmol/min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

To acquire data for adequate ultrafiltration (UF) control, sodium and potassium balance was investigated during hemodialysis (HD) in 16 hemodialyzed patients. Overall balances were evaluated from concentration measurements of the in- and outflowing dialysate and pre- and postdialysis plasma. The diffusive and convective part of the electrolyte removal and its intra- and extracellular space (ICS, ECS) component were calculated. During a 5-h HD, 40-110 mmol of potassium is removed, predominantly by diffusion (72-88%). Calculation shows that 40-70% of the removed amount is taken from the ICS. Sodium's overall HD showed much higher scatter, ranging from positive values to 500 mmol removal. The diffusive component was positive in most cases. By ultrafiltration sodium is removed in all cases. Calculations also showed in all cases that sodium was delivered to the ICS. This is in contradiction with the general belief that exchangeable sodium is distributed solely in ECS (1,2,6,7). This may be a sign of the effort to keep changes of ICS osmotic load at a minimum. Based on the finding of the exchange of sodium for potassium in the cellular wall, a method has been devised to calculate the UF fraction removed from EC (UFEC) expressed as a coefficient KEC = UFEC/UFToT, with UFToT being the total fluid volume removed during the HD session.

The aim of this crossover clinical study was to gain basic information on the hemocompatibility and effectiveness of recently developed high-flux membranes made of cuprammonium rayon with ultrafiltration coefficients of 10, 17, and 19 ml/mm Hg/h (S12W, SU12W, and SS12W dialyzers, respectively), and to identify any possible differences from a conventional membrane made of the same material with an ultrafiltration coefficient of 6 ml/mm Hg/h (C12W dialyzer). All the tested membranes led to an abrupt drop in leukocyte count in the initial phase of hemodialysis. In high-flux membranes, C5a anaphylatoxin would pass into the dialysate, but mean C5a anaphylatoxin concentrations in the dialysate were lower by orders of magnitude than its plasma concentrations, which behaved, in high- and low-flux membranes alike, typically of those made of nonsubstituted cellulose with no intermembrane differences. As judged by the concentrations of the thrombin-antithrombin III complex, the coagulation system was activated--again, without differences between membranes. The reduction rates for urea, creatinine, and phosphates were comparable for all the tested membranes. Compared with baseline, the post-dialysis serum concentrations of beta 2-microglobulin in high-flux membranes, unlike the low-flux membrane, were significantly lower. We conclude that there are no significant differences between the tested high- and low-flux membranes made of cuprammonium rayon in the monitored hemocompatibility parameters, and that high-flux membranes are capable of reducing serum beta 2-microglobulin concentrations.

Planning of future needs of Renal Replacement Therapy (RRT) Programme is frequently based on comparison of national data with data from other countries. Often, the dynamics of RRT development is disregarded and dialysis and transplantation assessed as separate entities, too. Such approach may lead to underestimation of present level of RRT availability and overestimation of immediate future needs. Transplantation activity and number of patients requiring dialysis are interrelated variables. Under steady state, their relation may be described as N = TX + U where N denotes incidence of chronic renal failure, TX transplantation activity, and U stands for mortality rate of dialysed population. Considering mortality rate equal to 10% of dialysed population (P), an equation describing the interrelation of transplantation activity and number of patients requiring dialysis may be devised: P = (N - TX)/0.1. This equation can be used to calculate target values of RRT programme. The time course of RRT needs to reach the target figures may be predicted from a simple differential equation dP/dT = N - 0.1. P - TX, taking into account dynamic character of this process.

Well defined dry weight is a must for adequate UF control during haemodialysis (HD). However, interdialytic weight gain (delta BW) must not be excessive. delta BW is closely related to interdialytic thirst which in turn is strongly influenced by post-dialysis plasma sodium (CPNa post), but little is known about the desired CPNa post. The points below serve as a basis for establishing this value. a) Thirst is mediated by osmoreceptors. b) A strong correlation has been found between delta BW and intradialytic increase in plasma sodium but no such correlation exists with the interdialytic increase in plasma urea. This indicates that fluid intake between dialyses depends solely on electrolytes. c) Pre-dialysis plasma sodium in an individual is stable, indicating that the patient is at his "set value" of electrolyte osmolality. d) Half of the potassium removed during HD comes from the extra- and half from the intracellular space. Assuming that it is desirable not to disturb a patient's pre-dialysis osmotic steady state, it can be calculated that the desired CPNa post should be higher than the pre-dialysis value by half of the intradialytic plasma potassium drop, i.e., approx. CPNa post = CPNa pre + 1 to 2 mmol/l.

High-flux dialysers are frequently used for highly efficient ultrashort treatment schedules. To avoid the risk of inadequately low dialysis dose in this treatment strategy where 'every minute counts', it is often advocated to monitor the treatment quality by means of urea kinetic modelling (UKM). However, careful computational analysis of concentration curves generated by UKM versus more realistic two-pool model curves indicates the risk of substantial overestimation of the protein catabolic rate (PCR). Therefore conventional UKM should not be used to monitor and/or guide treatment schedules with dialyser urea clearance greater than 250 ml/min and dialysis time less than 3 h. Under these conditions, PCR can be overestimated by as much as 20%.

The paper presents a computational study dealing with the patient's response to the change in dialysis time schedule from 7 hours twice a week to 4 hours thrice a week. The problem is treated in a purely mathematical way, based on a 3-pool model of the patient-artificial kidney system (one compartment represents patient's intracellular and extracellular volume, respectively, one compartment is reserved for description of the artificial kidney itself). The calculation was performed for two extreme values of intercompartmental permeability coefficient K and for two different values of dialysance of the dialyzer used. The results obtained are presented in form of graphs and tables and are in excellent accordance with the clinical results reported recently by Válek and co-workers.

The empirical dialysis therapy of acute renal failure should be replaced by modern scientific methods of treatment. The classic indications for hemodialysis are hyperkaliemia, hyperhydratation, acidosis and uremia. While previously a dialysis was indicated in a concentration of blood urea nitrogen of more than 70 mmol/l today a serum level of 30 mmol/l is recommended. By the kinetic urea-modelling an individualized and effective dialysis-guidance is possible. The important data may be determined by a simple computer program in few seconds.

The aim of this study was to confirm or to reject whether plasma concentrations of individual fractions of middle molecular weight substances can become parameters for an adequate dialysis treatment and whether there exists a relation between that and some symptoms and signs in patients on regular dialysis. No changes in clinical condition, plasma concentration of middle molecules, or metabolic state after 5 years of short-time dialysis schedule were established. No difference was found in the plasma concentration of middle molecules after 6 months of continuous ambulatory peritoneal dialysis and in patients undergoing hemodialysis treatment. There was also no difference in glomerular filtration rate, blood urea concentration, dialysis index, and duration of regular dialysis treatment in patients with a middle molecular fraction 2 level lower and higher than 5.5 U/L. Elimination of fractions 2-4 and 6 by a 1-m2 Cuprophan coil dialyzer was similar to the elimination of creatinine. Only patients with acute respiratory infection had a fraction 2 higher than controls. Neither conventional parameters nor plasma concentrations of middle molecules can be indicators of an adequate dialysis. The well-being of patients and their metabolic state are the only criteria.

A precise dosage of heparin is necessary especially in acute dialysis, but also in chronic dialysis. This can be checked by measuring the partial thromboplastin time, the thrombin time, the coagulation time according to Lee-White or, recently, by automatic measurement of activated whole-blood coagulation. For the latter only 0.5 ml of whole blood is necessary. In a total of 44 examinations the activated whole-blood coagulation time was shown to be well reproducible. In the 40 patients examined there was considerable variation in the sensitivity to and the elimination rate of heparin, which indicates the necessity of individual heparin dosage. Measuring the activated whole-blood coagulation time proved to be suitable for classifying the patients.