Nutritional status and volume control in adolescents on chronic hemodialysis.

BACKGROUND: Pediatric patients on maintenance hemodialysis (HD) are at risk of both malnutrition and fluid overload. This pilot study aimed to assess correlates of normalized protein catabolic rate (nPCR) in adolescents on chronic HD, in particular fluid status markers. METHODS: All patients aged 10-18 years on chronic HD in our center between 2017 and 2019 were enrolled. For each patient, mean nPCR was calculated and correlations with the following parameters investigated: dry body weight change in subsequent 3 months in kg (∆BW) and percentage of BW (∆BW%), change in body mass index (∆BMI), preHD systolic and diastolic blood pressure (SBP, DBP), residual urine output, biochemistry, and blood volume monitoring-derived first hour refill index (RI), calculated as ratio between ultrafiltration rate and reduction in relative blood volume in first hour of dialysis. RESULTS: Seventy-nine nPCR determinations were collected in 23 patients, median age 14.8 years. nPCR significantly correlated with ∆BW, ∆BW%, ∆BMI, spKT/V, and preHD serum creatinine, and negatively correlated with age, DBP SDS (r=-0.466, p=0.025) and RI (r=-0.435, p=0.043). RI was significantly higher in patients with nPCR <1 than those with nPCR above this threshold: 3.2 (1.9-4.7) vs. 1.4 (0.7-1.8) ml/kg/h/% (p=0.021). At multivariable analysis, nPCR remained positively correlated with creatinine and spKt/V, and inversely correlated with RI. CONCLUSIONS: nPCR is a significant predictor of weight change in adolescents on maintenance HD, and seems associated with creatinine and dialysis adequacy. Inverse correlation with RI suggests possible associations between malnutrition and fluid overload, but larger prospective studies are needed to confirm this. A higher resolution version of the Graphical abstract is available as Supplementary information.

An improved method to estimate absolute blood volume based on dialysate dilution.

Online hemodiafiltration machines equipped with a blood volume monitor and the possibility to rapidly infuse exact amounts of ultrapure dialysate into the extracorporeal circulation can be used to determine absolute blood volume in clinical practice. The aim of the present study was to evaluate the reproducibility of such measurements. Intra-individual reproducibility was evaluated in four measurements taken in hourly intervals within the same dialysis treatment. Ten patients were studied. Absolute blood volumes measured at the beginning and after 1 hour of dialysis were significantly different (80.6 ± 14.5 and 63.9 ± 14.3 mL/kg, P < .001) and highly reproducible between the last three measurements (63.9 ± 14.3, 61.4 ± 13.8, and 60.9 ± 13.9 mL/kg, P = n.s.). Measurement of absolute blood volume after 1 hour of treatment is more precise than earlier measurements and might be better suited for guidance of ultrafiltration.

Progress in volume assessment for the hemodialysis patients. / è¡€æ¶²é€æžæ‚£è€ å®¹é‡è¯„ä¼°æ–°è¿›å±•.

Volume overload is widespread in the hemodialysis (HD) patients, which is closely related to cardiovascular complications, hospitalization rates, hospitalization costs, and mortality. Meanwhile it is an important independent prognostic risk factor. Some new technologies for volume assessment have made some progress and are gradually applied in clinical practice, such as blood volume monitoring, lung ultrasound examination, bioelectrical impedance analysis, and corrected flow time. The new technologies can provide clinicians more objective and efficient methods for assessing the volume status of the HD patients, which is beneficial to the HD patients because they can achieve an ideal volume balance and improve the prognosis.

Pediatric intradialytic hypotension: recommendations from the Pediatric Continuous Renal Replacement Therapy (PCRRT) Workgroup.

Intradialytic hypotension (IDH) is a common adverse event resulting in premature interruption of hemodialysis, and consequently, inadequate fluid and solute removal. IDH occurs in response to the reduction in blood volume during ultrafiltration and subsequent poor compensatory mechanisms due to abnormal cardiac function or autonomic or baroreceptor failure. Pediatric patients are inherently at risk for IDH due to the added difficulty of determining and attaining an accurate dry weight. While frequent blood pressure monitoring, dialysate sodium profiling, ultrafiltration-guided blood volume monitoring, dialysate cooling, hemodiafiltration, and intradialytic mannitol and midodrine have been used to prevent IDH, they have not been extensively studied in pediatric population. Lack of large-scale studies on IDH in children makes it difficult to develop evidence-based management guidelines. Here, we aim to review IDH preventative strategies in the pediatric population and outlay recommendations from the Pediatric Continuous Renal Replacement Therapy (PCRRT) Workgroup. Without strong evidence in the literature, our recommendations from the expert panel reflect expert opinion and serve as a valuable guide.

How to achieve accurate blood culture volumes: the BD BACTEC FX blood volume monitoring system as a measuring instrument and educational tool.

Collecting adequate volumes of blood in blood culture bottles is crucial for sensitive detection of bacteremia and fungemia. Tools enabling easy collection of data on the degree of blood culture bottle filling at different hospital departments are an important step toward quality measurement and improvement. In this study, we verified the accuracy of a software tool for the monitoring of blood culture bottle filling developed by Becton Dickinson, BD blood volume monitoring system (BVMS) that was adjusted for use on plastic BACTEC bottles, and evaluated its ease of use in routine practice. In total, 538 negative plastic BD BACTEC Plus Aerobic/F blood culture bottles collected in two secondary care hospitals in Belgium were included in the study. The BVMS software demonstrated good performance, with an acceptable mean difference of - 0.3 mL or - 4.0% between the mean volume estimated by BVMS and the mean weight-based volume. Data (mean blood volume and standard deviation) and figures (box-and-whisker and histogram plots) on blood culture bottle filling are easily acquired. They provide information on the current situation in a hospital (department) and can be used as a tool for quality improvement measurements and follow-up. Caution is required when interpreting BVMS results for hospital wards where a substantial amount of the bottles collected come from patients with hematocrit values < 30%. This study demonstrated that BVMS is a reliable and easy to use tool which facilitates monitoring and coordination of optimization of blood culture bottles filling by the clinical laboratory.

The first hour refill index: a promising marker of volume overload in children and young adults on chronic hemodialysis.

BACKGROUND: Volume overload is a known risk factor for cardiovascular complications in children on hemodialysis (HD), but a measurable index of volume overload is still lacking. METHODS: We propose a novel index of pre-HD volume overload based on blood volume (BV) monitoring, the first hour refill index (RI), calculated as the ratio between the ultrafiltration rate indexed for body weight during the first HD hour and the percent BV change at the first hour of the treatment. This parameter was retrospectively calculated in 121 sessions in 11 oligoanuric children and young adults on chronic HD, with median age 14.3 years (range 5.4-22.4), and its association with left-ventricular mass index, pre-HD blood pressure, and number of antihypertensive medications was evaluated. RESULTS: The median RI was 2.07 ml/kg/h/%. There was a significant correlation between RI and median LVMI (r 0.66, p = 0.028), which was 53.4 g/m2.7 (45.7-64) in patients with a median RI > 2, and 36.6 g/m2.7 (24.9-47) in those with a median RI < 2 ml/kg/h/% (p = 0.01). The number of antihypertensive drugs per patient was significantly higher in patients with a RI > 2 than in those with a RI < 2 ml/kg/h/% (three vs one per patient; p = 0.02) while blood pressure was not significantly different between the two groups. CONCLUSIONS: The ratio between the ultrafiltration rate per body weight and the BV change during the first hour of a HD session could be a promising index of refill capacity and pre-HD volume overload in children and young adults on chronic HD.

Blood pressure management in children on dialysis.

Hypertension is a leading cause of cardiovascular complications in children on dialysis. Volume overload and activation of the renin-angiotensin-aldosterone system play a major role in the pathophysiology of hypertension. The first step in managing blood pressure (BP) is the careful assessment of ambulatory BP monitoring. Volume control is essential and should start with the accurate identification of dry weight, based on a comprehensive assessment, including bioimpedance analysis and intradialytic blood volume monitoring (BVM). Reduction of interdialytic weight gain (IDWG) is critical, as higher IDWG is associated with a worse left ventricular mass index and poorer BP control: it can be obtained by means of salt restriction, reduced fluid intake, and optimized sodium removal in dialysis. Optimization of peritoneal dialysis and intensified hemodialysis or hemodiafiltration have been shown to improve both fluid and sodium management, leading to better BP levels. Studies comparing different antihypertensive agents in children are lacking. The pharmacokinetic properties of each drug should be considered. At present, BP control remains suboptimal in many patients and efforts are needed to improve the long-term outcomes of children on dialysis.

Blood volume-monitored regulation of ultrafiltration to decrease the dry weight in fluid-overloaded hemodialysis patients: a randomized controlled trial.

BACKGROUND: Because chronic fluid volume overload is associated with higher mortality, we tested whether blood-volume monitored regulation of ultrafiltration and dialysate conductivity (UCR) and/or regulation of ultrafiltration and temperature (UTR) would facilitate dry weight reduction, in comparison to conventional dialysis (CONV). METHODS: We carried out a multicenter, 4-week, randomized controlled trial in hemodialysis patients ≥15% above normal extracellular fluid volume (ECV), per bioimpedance spectroscopy, who were randomized 1:1:1. Applying UCR (Nikkiso), UTR (Fresenius) and CONV, initial dry weight was reduced rapidly to target. Dry weight reduction was attenuated and eventually stopped at the occurrence of dialysis complications. The primary outcome was defined as intra- and postdialytic complications. Secondary outcomes were magnitudes of dry weight and blood pressure reduction. RESULTS: Of 244 patients assessed, N = 95 had volume overload ≥15% above normal ECV. Fifty patients received the allocated interventions (N = 16 UCR, N = 18 UTR, N = 16 CONV) and completed the trial. The rate of complications was significantly lower in UTR compared to CONV (21 ± 21% vs 34 ± 20%, p = 0.022), and also compared to UCR (vs 39 ± 27%, p = 0.028), but not statistically different between UCR and CONV (p = 0.93). Dry weight reduction was significantly higher in UTR compared to UCR (5.0 ± 3.4% vs 2.0 ± 2.7% body weight, p = 0.013), but not compared to CONV (vs 3.9 ± 2.1% body weight, p = 0.31). Systolic blood pressure reduction throughout the intervention phase was 17 ± 22 mmHg overall, but not significantly different between the three groups. Average maximum ultrafiltration rates were significantly higher in UTR than in UCR and CONV, at statistically similar dialysis times. Retrospective examination of randomly selected hemodialysis sessions in the UCR group identified technical mistakes in 36% of the dialysis sessions, despite considerable training efforts. CONCLUSIONS: Even in patients with volume overload, fluid removal was challenging. Despite the relative advantage of UTR, which must be interpreted with caution in view of the poor technical execution of UCR, this study renders clear that fluid removal must not be reinforced rapidly. Apprehension of this obstacle is imperative for future clinical and academic endeavors aimed at improving dialysis outcomes by correcting volume status. TRIAL REGISTRATION: ClinicalTrials.gov ( NCT01416753 ), trial registration date: August 12, 2011.

A physiologically based model of vascular refilling during ultrafiltration in hemodialysis.

An assessment of fluid status can be obtained by monitoring relative blood volume (RBV) during hemodialysis (HD) treatment. The dynamics of RBV is determined by fluid removal from the intravascular compartment by ultrafiltration (UF) and vascular refill from the interstitium. To characterize this dynamics, a two-compartment model describing the short-term dynamics of vascular refilling and UF is developed. Fluid movement between the compartments is governed by lymphatic and microvascular fluid shifts. Further, protein flux is described by convection, diffusion and the lymphatic protein flux. Patient specific parameters are identified based on hematocrit (Hct) measurements by the Crit-Line monitor (CLM). Different measurement frequencies and UF profiles are compared to determine data fidelity and influence on the quality of parameter estimates. This relevant information can be used to assess the (patho)physiological status of hemodialysis patients and could aid in individualizing therapy.

Integrating Monitoring of Volume Status and Blood Volume-Controlled Ultrafiltration into Extracorporeal Kidney Replacement Therapy.

PURPOSE: Volume management in hemodialysis (HD) requires the ability to assess volume status objectively and determine treatment strategies that achieve euvolemia without compromising hemodynamic stability. The aim of this study was to compare dialysis with and without blood volume-controlled ultrafiltration (UF) in combination with body composition monitoring, and to evaluate indicators for adequate dialysis (Kt/V), ultrafiltration volume, fluid status, and the occurrence of intradialytic morbid events (IME). PATIENTS AND METHODS: Patients undergoing hemodialysis or on-line hemodiafiltration with support of a blood volume monitor (BVM) - a feedback control device integrated into the 5008 and 6008 HD systems - were enrolled. Patients received treatment for four weeks using the 6008 CAREsystem and the BVM (6008+). Data on dialysis dose (Kt/V), UF volume and predialysis fluid status were documented. This data was also documented retrospectively for four weeks with (5008+) and without (5008-) the use of the BVM with the 5008 system. Comparisons were analyzed using linear mixed models. RESULTS: Twenty-four patients were enrolled. Kt/V was unaffected by blood volume-controlled UF (5008- vs 5008+: p=0.230) and was equally achieved with both HD systems (5008+ vs 6008+: p=0.922). The UF volume and fluid status achieved were comparable, independent of the use of UF control with BVM (5008- vs 5008+; UF volume: p=0.166; fluid overload: p=0.390) or the HD system (5008+ vs 6008+: UF volume: p=0.003; fluid overload: p=0.838), except for UF volume being higher in the 6008+ phase. IMEs occurred in less than 3% of treatments, with no difference between study phases. CONCLUSION: This study demonstrates that a clinical approach to kidney replacement therapy that tracks volume status and manages intradialytic fluid removal by blood volume-controlled UF delivers adequate dialysis without compromising fluid removal. It maintains volume status and ensures low incidence of IMEs.

Feedback control of absolute blood volume: A new technical approach in hemodialysis.

INTRODUCTION: The success of automatic feedback control systems to improve hemodynamic stability by preventing relative blood volume from dropping beyond a critical value during dialysis is limited. The aim of this study was to use one of these systems for control of absolute rather than relative blood volume to prevent volume-dependent morbid events. METHODS: Dialysis was delivered by a machine providing feedback control of ultrafiltration rates, relative blood volume monitoring, and accurate bolus infusion of 240 mL of dialysate to measure absolute blood volume at the beginning of dialysis. Critical relative blood volume required by the control algorithm was calculated from absolute blood volume at the beginning and a critical absolute blood volume of 67 mL/kg. FINDINGS: In 40 stable patients, ultrafiltration was guided by blood volume using the feedback algorithm of the integrated program. Blood volume was maintained in a narrow range above the prespecified minimal value of 67 mL/kg. At the end of dialysis, absolute blood volume ranged from 67.5 to 72.5 mL/kg (69.4 ± 1.3 mL/kg). No volume-dependent intradialytic morbid event occurred. DISCUSSION: A feedback control system for relative blood volume-controlled ultrafiltration can be used for control of absolute blood volume. A prescribed target of absolute blood volume can be converted into relative blood volume, and this can subsequently be reached automatically with the integrated feedback system of the dialysis machine. Intradialytic morbid events could be considerably reduced. The whole procedure could be completely automated without altering the hardware of the dialysis device.

Meta-Analysis of Randomized Controlled Trials Using Tool-Assisted Target Weight Adjustments in Chronic Dialysis Patients.

INTRODUCTION: Technological adjuncts have been developed to improve the accuracy of fluid removal goals in maintenance dialysis recipients. We aimed to determine whether the introduction of these tools has been shown to impact clinical outcomes. METHODS: We performed a systematic review and meta-analysis of randomized controlled trials that compared fluid management guided by technological adjuncts to standard care in hemodialysis and peritoneal dialysis. The primary outcome was all-cause mortality. Secondary outcomes were cardiovascular events, hospitalizations, intradialytic hypotension, blood pressure, symptoms, antihypertensive medications. and left ventricular mass index. RESULTS: Of the 2940 citations retrieved, we identified a total of 12 eligible trials comprising 2406 participants. In the 10 studies (n = 2111) with data on mortality, the use of adjunct technologies was not associated with a reduction of mortality (rate ratio [RR]: 0.92; confidence interval [CI]: 0.57-1.51; I2 = 36%). The intervention conferred a reduction in systolic arterial pressure (mean difference: -3.14; CI: -5.89 to -0.38; I2 = 39%) but did not affect other outcomes. In a subgroup analysis, bioimpedance was associated with a reduced risk of hospitalization (RR: 0.68; CI: 0.46-0.99; I2 = 55%). The risk of bias was high or unclear in most studies and the quality of evidence was judged to be low. CONCLUSIONS: Among maintenance dialysis recipients, technological adjuncts for fluid management did not improve survival. Trials mostly investigated the use of bioimpedance, whereas the evidence for use of other technologies remain very scarce. Future adequately powered trials should assess a broader array of promising technologies using meaningful clinical outcomes over a prolonged follow-up duration.

Utility of a blood volume monitor in the management of anemia in dialysis by computing the total hemoglobin mass.

INTRODUCTION: The degree of interdialytic weight gain and ultrafiltration may influence anemia results in dialysis. The purpose of this study is to evaluate the utility of a blood volume monitor (BVM) in the management of renal anemia and its ability to avoid the variability of hematocrit (Hct) and hemoglobin values (Hb) depending on plasma volume through a simple method of monitoring the total hemoglobin mass (MtHb ). METHODS: Predialysis blood samples for measurement were drawn at both the midweek treatment and the beginning-of-the-dialysis-week treatment in 30 patients. The MtHb was calculated as MtHb = Vb × Hb, where Vb is the absolute blood volume determined by online dialysate dilution using an online hemodiafiltration machine incorporating a relative BVM. FINDINGS: The MtHb and the total red cell volume (VRBC ) as measured with the bolus method at the starting of the treatment were 540 ± 148 grams and 1544 ± 339 mL, respectively. There were significant differences between the Hb levels and between the hematocrit levels according to the time of dialysis. However, the MtHb remained constant. There was also an excellent correlation between the Hb measurements by the BVM and the blood sampling method (R = 0.89, P value <0.001). CONCLUSION: Our study suggests that BVM could be very useful in the management of anemia in dialysis by computing the total Hb mass in clinical practice and may support better and more appropriate assessments of the factors influencing circulating Hb.

Optimized Blood Volume Monitoring during Hemodialysis Procedure based on Ultrasonic Speed Measurement.

Fast reduction of blood water volume due to ultra-filtration via hemodialysis machine and critical threshold of blood water volume can result in clinical complications such as hypotension. When blood water volume reduces during hemodialysis process, the concentration of blood forming elements will increase. One of the methods for the monitoring of the concentration changes is ultrasonic speed measurement. In this paper, we optimize the ultrasonic speed measurement method in such a way that it would be compatible with conventional air detector in a hemodialysis machine. Air bubble detecting and the relative blood water volume estimating can be achieved by adding the "sing-around" ultrasonic speed measurement method to the current hemodialysis machine; air bubble detection is achieved by monitoring the decline in the ultrasonic wave amplitude (because of air bubbles) and the protein concentration measurement is achieved by measuring the transit time of the wave. Therefore, the optimized method can be applied to the air detection device of a hemodialysis machine.

Effects of biofeedback dialysis mode of blood volume monitoring on cardiac function in the maintenance hemodialysis patients with intra-dialytic hypotension / 中国医师杂志

Objective:To discuss the effects of biofeedback dialysis mode of blood volume monitoring on cardiac function in the maintenance hemodialysis (MHD) patients with intra-dialytic hypotension (IDH).Methods:40 patients who underwent maintenance hemodialysis in Suzhou Hospital Affiliated to Nanjing Medical University from September 2018 to December 2020 and had IDH for many times were selected. They were divided into standard dialysis (SHD) group and biofeedback dialysis mode of blood volume monitoring (BVM) group, with 20 cases in each group. In the first 12 weeks of the first stage, the patients in both groups were treated with standard dialysis, and in the second 12 weeks, they were treated with maintenance hemodialysis according to standard dialysis and biofeedback dialysis mode of blood volume monitoring. The incidence of IDH and the changes of blood pressure before and after dialysis, body weight, ultrafiltration volume, B-type brain natriuretic peptide (BNP), left ventricular ejection fraction (LVEF), left ventricular end diastolic diameter (LVEDD), left ventricular posterior wall thickness (LVPW), inlet ventricular septal defect (IVSD), mitral valve flow spectrum E/A value (E/A) and left ventricular mass index (LVMI) were observed.Results:(1) In the second stage of treatment, the number of IDH requiring nursing intervention in BVM group was significantly lower than that in SHD group ( P<0.05). (2) The difference of blood pressure change in BVM group during the second stage of treatment was significantly lower than that in the first stage and SHD group ( P<0.05). (3) In the second stage of treatment, the ultrafiltration volume of patients in BVM group was significantly higher than that in the first stage, and the BNP and body weight were significantly lower than that in the first stage (all P<0.05). However, the body weight, BNP and ultrafiltration volume of patients in SHD group had no significan change in the two stages of treatment (all P>0.05). (4) After treatment, the LVID, LVPW, IVSD and LVMI in BVM group were significantly lower than those before treatment, and LVEF and E/A were significantly higher than those before treatment (all P<0.05). However, there was no significant change in echocardiographic indexes in SHD group before and after treatment (all P>0.05). Conclusions:The biofeedback dialysis mode of blood volume monitoring can significantly reduce the occurrence of IDH, and this dialysis mode can effectively improve the cardiac function of MHD patients with hypotension.

Determination of the critical absolute blood volume for intradialytic morbid events.

The reduction of blood volume below a critical threshold is assumed to trigger intradialytic morbid events (IME). Recently, we presented a simple method to determine the absolute blood volume during routine hemodialysis (HD) carried out without blood sampling and without injection of dyes or radiolabeled markers. Such information could be used to detect excessive volume reduction during HD and to prevent IME. Therefore, we performed a pilot study in IME-prone patients to identify the absolute blood volume at which they developed clinical symptoms. A volume of 240 mL of ultrapure dialysate was automatically infused into the extracorporeal circulation using the bolus function of a commercial online hemodiafiltration machine incorporating a blood volume monitor (BVM). The increase in relative blood volume (RBV) caused by the infusion was measured and used to determine the absolute blood volume at that time. The blood volume per kilogram body mass at the time of symptomatic IME was also determined. All IME-prone patients of a single-dialysis center were included in the study. Ten out of 12 patients became symptomatic at a specific blood volume between 65 and 56 mL/kg (mean 62 mL/kg) whereas RBV showed a wide scatter (82-97%). A specific blood volume of 65 mL/kg seems to represent the threshold for IME by this method. The technique could be completely automated without altering the hardware of the dialysis device. Present feedback systems for automated blood volume-controlled ultrafiltration could be adapted to maintain absolute blood volume above this critical volume to safely prevent volume-dependent IME.

Effects of Blood Volume Monitoring on the Rate of Positive Blood Cultures from the Emergency Room / 대한임상미생물학회지

BACKGROUND: Blood cultures are essential in diagnosing and treating sepsis. There are several factors that affect the diagnostic yield of blood cultures such as the number of blood sampling episodes, the incubation period, the type and volume of culture media, and the amount of blood drawn. This study aimed to elucidate whether monitoring the volume of blood drawn with an educational intervention could affect the diagnostic quality of blood cultures. METHODS: We implemented quality monitoring for the blood volume drawn during blood culture testing for adults in an emergency room. We instructed the nurses in the emergency room to draw the optimal amount of blood and to reduce the number of blood culture sets from three to two. We analyzed and compared the amount of blood drawn, the rate of positive blood cultures, the contamination rate, and time to positivity (TTP) between 908 patients pre-intervention and 921 patients post-intervention. RESULTS: The amount of blood drawn increased from 0.7±0.3 mL per bottle (pre-intervention) to 6.5±1.7 mL per bottle (post-intervention) (P<0.0001). The rate of positive blood culture post-intervention (12.14%) was higher than that pre-intervention (6.65%) (P<0.0001). The contamination rate post-intervention (1.82%) was also significantly greater than that pre-intervention (0.60%) (P<0.0001). Except for anaerobes, there was no significant difference in the distribution of microorganisms between the pre- and post-intervention periods. The TTP for anaerobe bottles post-intervention was significantly shorter than that of pre-intervention (16.1±16.3 versus 18.6±18.3 h). CONCLUSION: This study suggests that continuing education about adequate blood volume and aseptic techniques is needed to increase the rate of positive blood cultures and reduce the contamination rate of blood cultures.

Continuous Blood Volume Monitoring and Ultrafiltration Control.

Continuous blood volume monitoring (CBVM) is believed to be a promising method for making the determination of patients' "dry weight" more objective, and ultrafiltration (UF) control more appropriate. Although blood volume response to UF and the interrelation between blood volume changes and changes in hemodynamic parameters are highly individual, certain principles of this response and interrelation can be identified and exploited for effective use of CBVM. The present work summarizes the authors' findings from practical CBVM application over the past 5 years and their opinions on the future development of this method. Four distinct types of blood volume response to constant UF rate were identified: Type 1, flat line throughout the whole session; Type 2, flat line during the first part of dialysis, followed by a linear decrease during the remaining time; Type 3, linear decrease right from dialysis start; and Type 4, linear decrease first, followed by a flat line during the remaining time. The possibility of a shift from one type to the other was verified. Blood volume reduction due to UF was found to have a static and a dynamic component. The most important factors affecting both components were found to be, by sensitivity analysis of a three-pool kinetic model, degree of overhydration, vascular system compliance, and UF volume (for the static component); and UF coefficient of the capillary wall and UF rate (for the dynamic component). Type 3 response, induced by more vigorous UF, was found to significantly decrease the volume of residual daily diuresis on the first postdialysis day. If confirmed, this finding may serve as a basis for the response type choice in patients with still significant residual renal function. Exploitation of the existence of dynamic blood volume reduction component for the first generation of automated biofeedback UF controllers may be complemented by automated identification of patient's plasma refilling capacity and/or position of his/her point on the Guytonian pressure/volume characteristics curves, and thus may more advanced "intelligent" UF controllers be constructed in the future.