Ultrafiltration Control Research Articles

Effects of pre-chlorination on ultrafiltration process in directly treating seasonal high-turbidity surface water: Membrane fouling control and shock load resisting

The seasonal high turbidity in the surface water is posing great challenges to the feasibility of direct ultrafiltration (UF) due to the severe membrane fouling. In this study, a direct UF process was employed to treat the high-turbidity surface water. With the conventional operational protocols, severe membrane fouling encountered. Model fitting indicated that membrane fouling, resulting from the UF of high turbidity water, was predominantly associated with the complete obstruction of pores on the surface of the membrane and the subsequent formation of a cake layer. A pre-disinfection process using sodium hypochlorite was developed in this study, and the membrane fouling was significantly mitigated during long-term (885 h) filtration. The optimized chlorine dosage was 1.5 mg/L in treating the 800 NTU surface water, and enabled the transmembrane pressure (TMP) stabilization of UF process at a low level (<10 kpa). Pre-disinfection can effectively inactivate microorganisms and diminish the presence of microbial extracellular polymeric substances (EPS). This results in a transition from complex and viscous fouling to inorganic fouling on the cake layer caused by high turbidity water. With pre-chlorination, the adhesion force of the cake layer attached on the membrane reduced significantly to make the fouling more easily detach and be removed from on the membrane surface by the shear stress caused by the hydraulic backwash. These findings are expected to develop new insights into the membrane fouling control of UF in directly treating the seasonal high-turbidity surface water.

Closed Loop Ultrafiltration Feedback Control in Hemodialysis: A Narrative Review.

While life-sustaining, hemodialysis is a non-physiological treatment modality that exerts stress on the patient, primarily due to fluid shifts during ultrafiltration. Automated feedback control systems, integrated with sensors that continuously monitor bio-signals such as blood volume, can adjust hemodialysis treatment parameters, e.g., ultrafiltration rate, in real-time. These systems hold promise to mitigate hemodynamic stress, prevent intradialytic hypotension, and improve the removal of water and electrolytes in chronic hemodialysis patients. However, robust evidence supporting their clinical application remains limited. Based on an extensive literature research, we assess feedback-controlled ultrafiltration systems that have emerged over the past three decades in comparison to conventional hemodialysis treatment. We identified 28 clinical studies. Closed loop ultrafiltration control demonstrated effectiveness in 23 of them. No adverse effects of closed loop ultrafiltration control were reported across all trials. Closed loop ultrafiltration control represents an important advancement towards more physiological hemodialysis. Its development is driven by innovations in real-time bio-signals monitoring, advancement in control theory, and artificial intelligence. We expect these innovations will lead to the prevalent adoption of ultrafiltration control in the future, provided its clinical value is substantiated in adequately randomized controlled trials.

Allo-Hemodialysis, a Novel Dialytic Treatment Option for Patients with Kidney Failure: Outcomes of Mathematical Modelling, Prototyping, and Ex Vivo Testing.

It has been estimated that in 2010, over two million patients with end-stage kidney disease may have faced premature death due to a lack of access to affordable renal replacement therapy, mostly dialysis. To address this shortfall in dialytic kidney replacement therapy, we propose a novel, cost-effective, and low-complexity hemodialysis method called allo-hemodialysis (alloHD). With alloHD, instead of conventional hemodialysis, the blood of a patient with kidney failure flows through the dialyzer's dialysate compartment counter-currently to the blood of a healthy subject (referred to as a "buddy") flowing through the blood compartment. Along the concentration and hydrostatic pressure gradients, uremic solutes and excess fluid are transferred from the patient to the buddy and subsequently excreted by the healthy kidneys of the buddy. We developed a mathematical model of alloHD to systematically explore dialysis adequacy in terms of weekly standard urea Kt/V. We showed that in the case of an anuric child (20 kg), four 4 h alloHD sessions are sufficient to attain a weekly standard Kt/V of >2.0. In the case of an anuric adult patient (70 kg), six 4 h alloHD sessions are necessary. As a next step, we designed and built an alloHD machine prototype that comprises off-the-shelf components. We then used this prototype to perform ex vivo experiments to investigate the transport of solutes, including urea, creatinine, and protein-bound uremic retention products, and to quantitate the accuracy and precision of the machine's ultrafiltration control. These experiments showed that alloHD performed as expected, encouraging future in vivo studies in animals with and without kidney failure.

Evaluation of efficacy, outcomes and safety of infant haemodialysis and ultrafiltration in clinical use: I-KID a stepped wedge cluster RCT

Abstract Background Critically unwell babies in intensive care units may develop acute renal failure. Options for renal replacement therapy are limited by their small size and available technology. Objectives To determine the clinical efficacy, outcomes and safety profile of the NIDUS® (a novel infant haemodialysis device) for babies under 8 kg, compared with current renal replacement therapy. Design A clinical investigation using a non-blinded cluster stepped wedge design with paediatric intensive care units randomised to sequences. Setting Paediatric intensive care units in six UK hospitals. Participants Children under 8 kg who required renal replacement therapy for fluid overload or biochemical disturbance. Interventions Continuous renal replacement therapy was provided by the usual methods: peritoneal dialysis and continuous haemofiltration (during control periods) and by the NIDUS (during intervention periods), a novel device designed for babies with a smaller circuit and filter and volumetric control of ultrafiltration. Main outcome measures Primary outcome was precision of ultrafiltration compared with prescription; secondary outcomes included biochemical clearances, accuracy of reported ultrafiltration and mortality. Data sources Bedside study data collected by weighing bags of fluid entering and leaving the device were entered into the study database along with case descriptors. Some secondary outcome data was collected via the Paediatric Intensive Care Audit Network. Results Ninety-seven participants were recruited by study closure, 62 to control and 35 to intervention. The primary outcome was obtained from 62 control but only 21 intervention patients, largely because of technical difficulties using NIDUS. The analysis comparing the available primary outcomes showed that ultrafiltration with NIDUS was closer to that prescribed than with control: standard deviations controls 18.75, intervention 2.95 (ml/hour), adjusted ratio 0.13, 95% confidence interval (0.03 to 0.71); p = 0.018. The mean clearances for creatinine, urea and phosphate were lower on peritoneal dialysis than NIDUS, which were in turn lower than continuous veno-venous haemofiltration. The variability in the clearances was in the same order. Of the 62 control patients, 10 died (2/62 on peritoneal dialysis; 7/13 on continuous haemofiltration) before discharge from paediatric intensive care unit (16%), compared with 12 out of 35 (34%) in the NIDUS group: p = 0.04, 95% confidence interval for difference (0 to 36%). Harms No important adverse events occurred and the NIDUS has an acceptable safety profile compared with other renal replacement therapies in this critically ill population with multi-organ failure. Mortality was lowest for Peritoneal Dialysis, highest for continuous haemofiltration, with the NIDUS in-between. Only one serious adverse device event which was reported to the Medicines and Healthcare products Regulatory Agency. Conclusions NIDUS works effectively, delivering appropriate blood clearances and accurate, controllable fluid removal (ultrafiltration), indicating that it has an important place alongside other dialysis modalities for infant renal replacement therapy. Future work Findings from this study indicate some modifications are required to NIDUS to improve usability. Further studies on use of the NIDUS device in other populations of babies for example those with chronic renal failure, and long-term outcomes are required. Trial registration This trial is registered as ISRCTN 13787486. Funding This award was funded by the National Institute for Health and Care Research (NIHR) Efficacy and Mechanism Evaluation Programme (NIHR award ref: 14/23/26) and is published in full in Efficacy and Mechanism Evaluation; Vol. 11, No. 1. See the NIHR Funding and Awards website for further award information.

Experimental and statistical study of an in-situ ultrasound (US)-assisted ultrafiltration process: Application to fouling control in skimmed milk filtration

In the present work, in-situ ultrasound was employed as an innovative technique for fouling control and membrane cleaning in ultrafiltration of skimmed milk solution. A response surface methodology (RSM) was used to examine the influence of operational parameters, including US power and frequency, solid concentration, and feed flow rate, on the performance of the US-assisted ultrafiltration process. The experiments were conducted without US irradiation initially, and the results were compared to those obtained through US-assisted filtration. Filtration performance was found to improve at higher levels of power and feed flow rate and at lower levels of US frequency and solid concentration. The total mass of permeate, permeate flux, and mass of particles retained on the membrane were determined for each run. The permeate flux was improved using US by >67 % at the optimum conditions of 100 w, 28 kHz, 0.5 wt%, 1 L/min). A novel synchrotron X-ray high contrast imaging technique available at the Canadian Light Source (CLS) was employed for real-time visualization of US-generated bubbles and its influence on fouling control. It was observed that the number and size of the microbubbles increased as the US power enhanced from 50 W to 100 W. Under the influence of the US frequency, significantly larger bubbles were created at 20 kHz, while microbubbles' size decreased when the frequency changed to 40 kHz. A non-phenomenological mathematical model was also developed to predict US-assisted ultrafiltration performance under the defined factor levels.

Process Analytical Technology (PAT) Implementation for Membrane Operations in Continuous Manufacturing of mAbs: Model-Based Control of Single-Pass Tangential Flow Ultrafiltration.

Control of single pass tangential flow ultrafiltration (SPTFF) is crucial for continuous manufacturing of monoclonal antibodies (mAbs). Integrating SPTFF technology into continuous manufacturing trains requires successful resolution of several challenges that arise due to the complexity of mass transfer interactions across multi-membrane configurations, the significant effect of feed material attributes and process variability on flux, and the need for advanced scheduling. In this paper, we propose a real-time, automated monitoring and control strategy for SPTFF in continuous processing of mAbs. The approach leverages a previously developed model for predicting the VCF across an SPTFF module based on the gel polarization model of protein ultrafiltration. A distributed control system (DCS) architecture was created for integrating the monitoring sensors and control elements, including NIRS sensors for concentration monitoring, as well as weighing balances, pressure sensors, pumps, and valves. Two different SPTFF control strategies were developed, firstly for final formulation of the drug product into the drug substance (ultrafiltration and diafiltration), and secondly for in-line concentration between two chromatography steps. Case studies were designed with 15 runs to test the strategy with a range of deviations induced in the feed and process conditions. The retentate concentration was controlled to within 10% of the target value in all runs. The combination of real-time sensor data and model-based control effectively enabled automated and tightly controlled operation of the SPTFF step and is a key enabler of quality by design in continuous mAb manufacturing.

In vitro measurements of ultrafiltration precision in hemofiltration and hemodialysis devices used in infants

BackgroundTo determine in vitro whether infant hemofiltration and hemodialysis devices can reliably deliver precise ultrafiltration (UF) control.MethodsWe tested the Prismaflex, Aquarius and NIDUS devices which have different circuit types, by in vitro testing with a bag of saline set up as a dummy patient, and monitoring fluid shifts by precise weighing. We looked for differences between the UF rates set and achieved and between the UF result the device displays to the clinician and the true volumes removed, which may lead to clinical errors. We performed short studies at UF settings of zero and 40 ml/h, and with and without simulating poor withdrawal and return lines, and simulated a 4-h treatment session.ResultsThe Prismaflex setting vs actual errors and display vs actual errors had wide variances, with SDs of 4.1 and 14.0 ml by 15 min, respectively, at both zero and 40 ml/h UF settings. The Aquarius values were wider at 17.3 and 30.3 ml, respectively. For the NIDUS, the mean UF errors were close to zero, and the variances were 0.17 ml. Stop-alarms induced by an obstructed line produced extra UF errors of up to 0.2 ml. A limitation was that we used crystalloid and not colloid for these tests.ConclusionsHemotherapy devices with conventional circuits available in the UK do not regulate UF control sufficiently well to recommend for use in small infants, but the NIDUS volumetrically controlled circuit does. All hemotherapy devices intended for small infants should be tested for UF precision. We were unable to test the CARPEDIEM or Aquadex devices.Graphical A higher resolution version of the Graphical abstract is available as Supplementary information

Prescription of online hemodiafiltration (ol-HDF).

HDF prescription should be able to satisfy the delivery of an optimal dialytic convective dose. Several factors are implicated in this endeavor. High blood flow rate is crucial to warranty processing an adequate blood volume and to ensure the highest shear rate per fiber needed to cleanse and prevent membrane fouling. A highly permeable dialyzer is needed with a surface area aligned to blood flow and performance needs. Anticoagulation requires specific adaptation in case of low molecular weight heparin use. By default, HDF prescription modality should ideally start by postdilution mode with a stepwise increment of convective dose by probing patient tolerance and efficacy. Alternative substitution modality should be considered if dialytic convective dose could not be achieved in the usual time frame. Convective dose prescription relies either on a manual mode (pressure control or volume control) or on automated mode (ultrafiltration control) depending on the technical options of the HDF machines. Dialysate flow rate is regulated by the HDF machine but should preferably keep constant dialysis fluid flowing the dialyzer with a Qb:Qd ratio of 1.4. Treatment time should not be reduced with HDF prescription. Treatment time should fit with patient tolerance (hemodynamic, osmotic, and solute shifts) and overall solute removal efficiency. Electrolytic prescription does not require specific adjustments as compared with conventional dialysis, but the patient needs to be monitored regularly and dialysate electrolyte adjusted to lab tests. A stepwise approach for implementing ol-HDF is preferable depending on the initial condition of the patient. Three particular cases may be considered: late-stage chronic kidney disease patient transitioning to renal replacement therapy, stable dialysis patient switching to HDF, and unstable or fragile patient or specific treatment schedule. Optimal dosing of HDF and personalized care to ensure treatment adequacy is the main goal for renal replacement therapy to improve patient outcomes. That should be ensured with HDF treatment.

BioLogic-HD™ and the problem of being (way) too far ahead of the market.

In the 1980s, I led a team to build a hemodialysis machine with sorbent regeneration of dialysate, ultrafiltration control, and single-needle access. The BioLogic-HD™ was perfectly suited for home hemodialysis, but not for in-center or acute dialysis. The home dialysis market in the United States was decimated by HCFA's decision in 1987 to stop paying for home helpers. As a result, our Venture Capital partners stopped supporting our small company, and the BioLogic-HD was never marketed. There is criticism of nephrologists for the lack of innovation in dialysis, but the major problem has been the commercialization of new dialysis technology.

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

PurposeVolume 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 MethodsPatients 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.ResultsTwenty-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.ConclusionThis 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.

Hemodialysis crossover study using a relative blood volume change-guided ultrafiltration control compared with standard hemodialysis: the BV-UFC study

BackgroundIt has been difficult to sufficiently achieve body-fluid management using blood volume (BV) monitor during hemodialysis (HD) with constant ultrafiltration (UF) rate. Recently, a relative BV change-guided UF control (BV-UFC) system was developed by combining the concepts of an automatic feedback system that could control the UF rate and profile with real- time monitoring of relative changes in BV (%ΔBV). However, this system has limited application in the clinical setting. Therefore, in this study, we aimed to perform the crossover study on HD with BV-UFC compared to standard HD in terms of hemodynamic stability during HD.MethodsForty-eight patients entered an 8-week crossover period of standard HD or HD with BV-UFC. Prevalence of intradialytic hypotension (IDH) as a primary outcome and changes in blood pressure (BP), differences in %ΔBV, and achievement of the target ultrafiltration volume as secondary outcomes were compared. IDH was defined as a reduction in systolic BP ≥20 mmHg from the baseline value at 10 min after HD initiation.ResultsNo significant differences were found in the prevalence of IDH, frequency of intervention for symptomatic IDH, and achievement of the target ultrafiltration volume between the groups. The %ΔBV was significantly fewer (-12.1 ± 4.8% vs. -14.4 ± 5.2%, p <0.001) in the HD with BV-UFC than that in the standard HD.ConclusionsHD with BV-UFC did not reduce the prevalence of IDH compared with standard HD. The relief of a relative BV reduction at the end of HD may be beneficial in patients undergoing HD with BV-UFC.Trial RegistrationUMIN, UMIN000024670. Registered on December 1, 2016.

Effect of filter depth of biological activated carbon on fouling control of ultrafiltration: performance and mechanism

Biological activated carbon (BAC) prefiltration is a common method to control fouling in ultrafiltration (UF) processes. BAC filter depth is a critical parameter for both design and operation of a prefiltration system. Here, the effect of filter depth on the performance and mechanism of contaminant removal and UF fouling characteristics was investigated. The results indicated that contaminants were mostly removed by the upper filter (0–10 cm), including organics, particles, and protein-like substances, while the deeper filter (10–50 cm) removed additional organics, which were mostly humic-like substances. The upper layer intercepted particles, which not only reduced the number of particles, but also significantly reduced the average particle size. The fouling control capability of BAC prefiltration was mostly attributed to the upper filter, whose function was greater than that of the deeper filter. However, the primary fouling mechanism did not vary with filter depth. In summary, during the combined process of BAC prefiltration and UF, when membrane fouling control is the main objective, the filter layer could be set as a thin layer (such as 10 cm). However, when the combined process needs to reduce the concentration of organic matter at the same time, a thicker layer is indispensable to achieve the desired performance.

Implementing PAT for single-pass tangential flow ultrafiltration for continuous manufacturing of monoclonal antibodies

Control of single pass tangential flow ultrafiltration is crucial for continuous manufacturing of monoclonal antibodies. We propose a strategy to control the output concentration of a continuous ultrafiltration step regardless of variations in the volume or concentration of the feed material. Scheduling algorithms for the filtration runs and cleaning cycles are developed, accounting for the expected cycle times of different unit operations in the continuous train. The complete design space for the membrane module is characterized experimentally. An empirical model of the design space is developed to predict the logarithmic relationship between the feed flowrate and the maximum concentration factors achievable in a single pass for feed concentrations in the range of 1–50 g/L and feed flowrates in the range of 10–210 mL/min. The control strategy leverages in-line concentration, flowrate and pressure sensors, including near infrared spectroscopy (NIRS) flow cells to measure the concentration of mAb in the feed and retentate streams in the range 0.5–200 g/L. The control elements are the permeate pump and a variable control valve on the retentate line, which are used to obtain the desired concentration factor across the module in a single pass. Two case studies are designed to test the control system under conditions of high feed flow rate and low feed concentration, and low feed flow rate and high feed concentration, respectively. Successful control is demonstrated in both cases. The proposed system is the first complete approach that integrates process understanding, advanced monitoring sensors, and control strategies to consistently achieve concentration targets over long continuous campaigns for production of monoclonal antibodies.

Convection flow optimization in online hemodiafiltration

Objective: to evaluate the dependence of the magnitude of convection flow in online hemodiafiltration (OLHDF) on ultrafiltration control method and patients’ individual characteristics. Materials and methods . The study included 36 stable dialysis patients (20 male and 16 female). The substitution rate was conducted manually based on transmembrane pressure (TMP). In some cases, devices with automatic filtration rate control unit AutoSub plus were used. The filtration rate (FR), TMP, blood flow rate (Qb), specific filtration rate (SFR, m/l/min/mm Hg –1 ) were recorded. Results. The maximum SFR in various patients ranged from 0.51 to 0.80 ml/min/mm Hg –1 ; average value was 0.62 ± 0.07 ml/min/mm Hg –1 . There was significant correlation of SFR with hemoglobin level (r = –0.55). SFR reduced during hemodiafiltration (on average – by 23 ± 4%). SFR was significantly affected by Qb (r = 0.70). Maximum SFR was achieved with a TMP of 140–220 mm Hg; with TMP over 250 mm Hg, a decrease in SFR was noted, an increase in Qb was required for further increase in FR. Individual stability of SFR was noted during serial observations; fluctuations in a particular patient did not exceed 10%. Substitution volume for the HDF session was 18.0 ± 3.3 L, the FR/Qb ratio was 24.7 ± 5.2%. Substitution volume of 21 L was not achieved in 17 of 36 patients. The use of automatic FR adjustment system made it possible to increase the substitution volume (SV) by 12–18%. Conclusion. Achieving maximum convection volume in OLHDF requires individualizing treatment parameters. The use of FR automatic control allows maximum possible convection flow.

Fouling control in ultrafiltration of secondary effluent using polyaniline/TiO2 adsorption and subsequent treatment of desorption eluate using electrochemical oxidation

Performance of three adsorbents, polyaniline-modified TiO2 (PANI/TiO2), Dow resin IRA(a) and Dow resin IRA(b), in removing organics from secondary effluent (SE) was evaluated, and the objective of this study is to deliver a treatment loop including membrane fouling control using adsorption and treatment of correspondingly formed desorption eluate using electrochemical oxidation, so that the contaminants could be effectively handled within a wastewater treatment plant. Results show that PANI/TiO2 is a promising adsorbent in the removal of effluent organic matter (>55%) and its regeneration was superior to the two others. Specifically, PANI/TiO2 could remove over 70% of the fraction of biopolymers from the SE and therefore alleviated subsequent membrane fouling to a large extent, while the other two presented less antifouling effect due to limited removal of the major foulants, though they both showed comparable effect as PANI/TiO2 in the removal of other organic fractions. BOD5/COD of the concentrated desorption eluate was gradually increasing along with the extension of the electrochemical oxidation. It reached >0.4 after 4.5 h of treatment, which is of suitable biodegradability for recycling to the influent of the wastewater treatment plant. The improvement on BOD5/COD was due to the mineralization of effluent organic matter and simultaneous minifying of their molecular size. Moreover, the operation cost of the treatment loop was estimated at about 0.12–0.15 USD/m3 for delivering effect fouling control and significant improvement on effluent quality.

Générateur de dialyse et hémodialyse à bas coût

An experimental model of a hemodialysis monitor has been developed to perform ultrafiltration control, and urea and creatinine clearance tests. This model allowed us to develop an original device that separates the used dialysate from fresh dialysate and to define the characteristics of an industrial prototype which ultimate objective is to reduce the costs of haemodialysis treatment in low and middle-income countries.

Hypotensive episodes on program hemodialysis during dialysis procedure: modern approach for diagnostics, prophylaxis and correction

The study objective is to evaluate the effectiveness of different approaches to correction and prevention of arterial hypotension episodes in patients undergoing long-term hemodialysis (HD). Materials and methods. The study included 35patients undergoing long-term hemodialysis in the dialysis center. In all patients, automatic non-invasive measurement of arterial pressure (AP) was performed using a built-in option of the “artificial kidney” device. Prior to the study, all patients underwent clinical test with evaluation of “dry weight” and bioelectrical impedance analysis. Crossover design was used in the study: at the beginning, hypotensive episodes were corrected in all patients using the standard method (the first 4 hemodialysis procedures); then during the following 4 procedures in addition to standard methods a computer algorithm automatically controlling ultrafiltration rate using an automatic system of pressure control (ASPC) with constant AP monitoring (AP was measured prior to hemodialysis and after it and at least 1 time in the first 5 min of the procedure; from the 4h procedure onwards, intervals were determined by the algorithm automatically) was used. Values of mean AP during hemodialysis procedures for the whole monitoring period were analyzed. The duration of the study was 3 weeks for all patients. Results . Mean pre-dialysis systolic and diastolic AP in the patients for the standard approach was 124.6 ± 27.7 and 74.5 ± 21.1 mm Hg, post-dialysis AP was 114.4 ± 24.4 and 71.3 ± 16.3 mm Hg, respectively. For ASPC, pre-dialysis and post-dialysis AP was statistically significantly higher than for the standard approach: 133.2 ± 21.3 and 79.3 ± 15.8 mm Hg (p &lt;0.001; p = 0.009), 125.7 ± 23.9 and 75.9 ± 18.3 mm Hg (p &lt;0.001; p &lt;0.001). Detailed analysis of intra-dialysis AP measured during the standard approach showed that it was 110.2 ± 17.3 and 68.3 ± 13.9 mm Hg. Using ASPC, intra-dialysis AP was significantly higher: 124 ± 20.5 and 75.9 ± 14.2 mm Hg (p = 0.03; p = 0.02). Mean AP was also higher: 82.5 ± 13.9 mm Hgfor the standard approach versus 91.5 ± 15.6 mm Hg (p = 0.01) for ASPC. The ultrafiltration rates were slightly higher without ASPC (8.2 ml/kg/hour vs. 7.9 ml/kg/hour). Therefore, it was shown that the use of ASPC in addition to standard methods of hypotension correction is effective and safe. There weren»t any significant differences in «hemodialysis-dose effectiveness» (Kt/V) in both groups; however, in the ASPC group target values of inorganic phosphorus in serum (for a dialysis patient) were reached which is one of the most important parameters of hemodialysis adequacy. Concentration of inorganic phosphorus for the ultrafiltration control algorithm was 1.5 mmol/l, for the standard dialysis program — 1.8 mmol/l which shows benefits of ASPC. This data didn»t reach statistical significance (p = 0.07) which likely can be attributed to a low number of observations. Conclusion . Intra-dialysis hypotension with high ultrafiltration rates is a frequent and potentially dangerous complication of hemodialysis which negatively affects patients» long-term prognosis mainly due to an increase in cardiovascular morbidity and mortality. A new method for prevention and correction of hypotension using ASPC allows to decrease ultrafiltration rate on time preventing a hypotensive episode, decreasing its rates and improving attainment of AP target values (both pre- and post-dialysis) as well as intra-dialysis variation during dialysis procedure.

A new approach in prevention and correction of intradialysis hypotension in patients on maintenance hemodialysis

The aim of the study was to evaluate the efficacy of various approaches to correcting and preventing hypotension episodes in patients on maintenance hemodialysis (HD).Material and methods. The study included 35 patients on maintenance hemodialysis in the Dialysis Center "MCHTP No. 1", which is a part of "B. Braun Avitum" network centers in the Russian Federation. All patients underwent an automatic blood pressure (BP) measurement using a machine-inbuilt option device for noninvasive blood pressure measurement. Prior to the study, all patients underwent a clinical test with a "dry weight" assessment and a bio-impedance analysis. The study had a cross-over design: first, all patients were treated using the standard methods for correcting hypotension episodes (at 4 initial procedures). Then, in the following 4 procedures, in addition to standard methods, a computer algorithm was used to automatically regulate the ultrafiltration (UF) rate: the automatic pressure monitoring system (biologic rr comfort) with continuous monitoring of blood pressure throughout the procedure; BP was recorded before and after the HD procedure, as well as at least once every 5 minutes during 3 initial procedures; and starting from the 4th procedure, the intervals were determined by the algorithm automatically. The average blood pressure values were analyzed during the dialysis procedures for the entire observation period. The duration of the study was 3 weeks for each patient.Results. The average predialysis blood pressures in the group with the standard approach to hemodynamic correction were 124.6 ± 27.7 and 74.5 ± 21.1 mm Hg, the postdialysis blood pressures were 114.4 ± 24.4 and 71.3 ± 16.3 mm Hg. With the use of automatic pressure monitoring system, the predialysis and postdialysis blood pressures were significantly higher than those with the standard approach: 133.2 ± 21.3 and 79.3 ± 15.8 mm Hg (p &lt; 0.001 and p = 0.009), vs. 125.7 ± 23.9 and 75.9 ± 18.3 mm Hg (p &lt; 0.001 and p &lt; 0.001), respectively. Upon closer examination of the intradialysis pressure variations, the intradialysis blood pressures were 110.2 ± 17.3 and 68.3 ± 13.9 mm Hg when measured by using the standard approach, and significantly higher: 124 ± 20.5 and 75.9 ± 14.2 mm Hg when the automatic pressure monitoring system was used (p = 0.03; p = 0.02). Also, higher mean arterial pressures were noted: 82.5 ± 13.9 with the standard approach vs.91.5 ± 15.6 mm Hg (p = 0.01) with the automatic pressure monitoring system. Studying UF rates, we found that the UF rate was slightly higher without using the automatic pressure monitoring system (8.0 ml/kg/h vs. 7.9 ml/kg/h). Thus, the new approach used in addition to the standard methods of correcting hypotension was effective and safe. No significant differences were seen in Kt/V values. However, when automatic pressure monitoring system was used in patients, the target phosphate levels were achieved: the inorganic phosphorus value was 1.5 mmol/L when using the UF control algorithm vs. 1.8 mmol/L with a standard dialysis program. However, these data did not reach the statistical significance (p = 0.07).Conclusion. Intradialysis hypotension and high UF rates remain frequent and potentially dangerous complications of HD procedure, which worsen the long-term prognosis of patients on HD, mainly due to the increase in cardiovascular morbidity and mortality. The new approach to the prevention and correction of hypotension by using the automatic pressure monitoring system allows one to reduce the UF rate in a timely manner, preventing the development of hypotension episodes, reducing their rates, and improving the achievement of target blood pressure values, both preand postdialysis, as well as intradialysis blood pressure variations.

A Differential Optical Sensor for Non-Invasive Real-Time Monitoring of Ultrafiltration Rate in Hemofiltration Therapies

Hemofiltration (HF) is a group of blood purification therapies used to treat patients with kidney injury. HF works using a process called ultrafiltration (UF) that removes excess liquid accumulated in the patient’s body caused by lack of excretion. UF progress is monitored by the HF machine, but the state-of-the-art method is cumbersome and could be more accurate. In this paper, a system composed by two optical sensors is proposed for real-time non-invasive estimation of ultrafiltration rate. This new system is simple, rugged, and low-cost and operates on sound theoretical foundations. The sensor system has been tested with two different experimental protocols and showed good correlation between its output and the reference value of the ultrafiltration rate (R2 = 0.97), as well as improved accuracy compared with the available commercial machine ( $\simeq 12$ ml/h). This system also has the potential to simplify the architecture required by critical care blood purification machines to perform UF control.

Hemodiafiltration versus conventional hemodialysis: Should "conventional" be redefined?

In the 1980s, conventional hemodialysis was considered as dialysis with acetate dialysate, dialysis machines without volumetric control, low blood flow and low-flux dialyzers; in the 1990s, the concept of conventional hemodialysis changed due to technological advances in dialysis machines, control of ultrafiltration and the widespread use of bicarbonate dialysate, which allowed an increase in blood flow and the use of synthetic high-flux dialyzers. To avoid backfiltration-induced adverse reactions, exogenous replacement fluid was promoted but its adoption was limited for technical and financial reasons. This scenario changed in 1995 with the development of on-line hemodiafiltration (HDF) techniques using the dialysis fluid itself as a replacement fluid. Dialysis machines were modified to perform on-line HDF, incorporating safety filters to ensure the quality of this replacement fluid (ultrapure dialysate). After more than two decades of clinical experience and technological development with high-volume HDF, the present article discusses whether HDF can currently be considered as the standard conventional treatment for chronic hemodialysis patients. A review of the evidence indicates that the time has come to consider HDF as the conventional hemodialysis treatment for the following reasons: first, technological development in water treatment and advances in dialysis machines, as well as the widespread use of synthetic high-flux dialyzers has made it a feasible proposition. Second, there is an absence of published literature showing any undesirable effects. Finally, scientific evidence is available showing the superiority of HDF over hemodialysis in overall and cardiovascular mortality in both prevalent and incident patients.