The use of SDS-PAGE scanning of spent dialysate to assess uraemic toxin removal by dialysis.

BACKGROUND: Uraemic toxins in the 8 to 60 kDa molecular weight range have been attracting increasing attention in dialysis therapy. However, there are no available standardized methods to evaluate their removal. Using new filtering membranes, we evaluated SDS-PAGE of spent dialysate to assess cut-off ranges and removal capacities into dialysate, while also measuring classical markers of dialyser function. METHODS: Eighteen dialysis patients were washed out for 2 weeks with FX 100 (Helixone(®)), followed by randomization to Xevonta Hi 23 (Amembris(®)) or FX dialysers for 2 weeks, then crossed over for an additional 2 weeks, and finally placed on Xenium 210 (Purema(®)) for 2 weeks. SDS-PAGE scanning of the removed proteins contained in the spent dialysate was performed during all dialysis sessions. Total mass of urea, creatinine, total proteins, beta 2 microglobulin (ß2m), retinol-binding protein (RBP) and albumin were measured. The reduction rates of serum urea, creatinine, ß2m, leptin, RBP, alpha 1-antitrypsin, albumin and total proteins were also determined. RESULTS: SDS-PAGE scanning identified four major protein peaks (10-18, 20-22.5, 23-30 and 60-80 kDa molecular weight) and showed clear differences in the amounts of removed proteins between the dialysers, particularly in the 20-22.5, 23-30 and 60-80 kDa ranges. Total mass of removed ß2m, RBP and albumin were in agreement with SDS-PAGE, while serum assays showed differing results. CONCLUSIONS: SDS-PAGE scanning provided a good characterization of protein patterns in the spent dialysate; it extended and agreed with protein determinations and allowed a better assessment of dialyser performance in removing 10 to 80 kDa molecular weight substances. It also identified differences between the three mainly filtrating polysulfone dialysers that were not detected with blood measurements.

Use of spent dialysate analysis to estimate blood levels of uraemic solutes without blood sampling: urea.

BACKGROUND: Urea kinetic modelling-based methods are widely used to assess dialysis efficacy. However, they require blood sampling and are susceptible to a number of errors, mainly from the calculated parameters (particularly V). Spent dialysate determinations have been used and have been shown to be reliable and simple to use. In this study, we associated dialysate-based and clearance determinations along with Kt/V to estimate blood urea levels. METHODS: Urea kinetic modelling, continuous sampling of spent dialysate and ionic dialysance were determined in 18 stable dialysis patients during 126 dialysis sessions. Mean blood urea levels were estimated as follows: mean urea level = spent dialysate - urea mass/(dialysance T). Blood urea levels before and after dialysis were calculated based on the same determinations and extended formulae. RESULTS: Estimated mean urea level was significantly correlated with measured mean blood urea level (R(2) = 0.957; P < 0.0001), and Bland and Altman analysis showed significant agreement between estimated and measured levels. Estimated and measured blood urea levels were also correlated before and after dialysis (R(2) = 0.972 , P < 0.0001 and R(2) = 0.903 , P < 0.0001, respectively), with good agreement for both blood urea before and after dialysis and their respective estimates. CONCLUSIONS: Blood urea levels may be reliably estimated from the total mass of urea removed in the dialysate and the dialysance measured during dialysis. Coupling both measurements allows a precise monitoring of dialysis efficacy and a specific evaluation of the patient's urea metabolism status. Technical dysfunctions and patient variations may be easily identified using this approach without blood sampling.

Measuring intradialyser transmembrane and hydrostatic pressures: pitfalls and relevance in haemodialysis and haemodiafiltration.

BACKGROUND: Post-dilutional haemodiafiltration (HDF) with high convection volumes (HCVs) could improve survival. HCV-HDF requires a significant pressure to be applied to the dialyser membrane. The aim of this study was to assess the pressure applied to the dialysers in HCV-HDF, evaluate the influence of transmembrane pressure (TMP) calculation methods on TMP values and check how they relate to the safety limits proposed by guidelines. METHODS: Nine stable dialysis patients were treated with post-dilutional HCV-HDF with three different convection volumes [including haemodialysis (HD)]. The pressures at blood inlet (Bi), blood outlet (Bo) and dialysate outlet (Do) were continuously recorded. TMP was calculated using two pressures (TMP2: Bo, Do) or three pressures (TMP3: Bo, Do, Bi). Dialysis parameters were analysed at the start of the session and at the end of treatment or at the first occurrence of a manual intervention to decrease convection due to TMP alarms. RESULTS: During HD sessions, TMP2 and TMP3 remained stable. During HCV-HDF, TMP2 remained stable while TMP3 clearly increased. For the same condition, TMP3 could be 3-fold greater than TMP2. This shows that the TMP limit of 300 mmHg as recommended by guidelines could have different effects according to the TMP calculation method. In HCV-HDF, the pressure at the Bi increased over time and exceeded the safety limits of 600 mmHg provided by the manufacturer, even when respecting TMP safety limits. CONCLUSIONS: This study draws our attention to the dangers of using a two-pressure points TMP calculation, particularly when performing HCV-HDF.

The CKD plasma lipidome varies with disease severity and outcome.

BACKGROUND: Various alterations in lipid metabolism have been observed in patients with chronic kidney disease (CKD). OBJECTIVES: To determine the levels of lipid species in plasma from CKD and hemodialysis (HD) patients and test their association with CKD severity and patient outcome. METHODS: Seventy-seven patients with CKD stage 2 to HD were grouped into classes of CKD severity at baseline and followed-up for 3.5 years for the occurrence of transition to HD or death (combined outcome). Plasma levels of phosphatidylcholines (PCs), lysophosphatidylcholines (LPCs), sphingomyelins (SMs), and fatty acids were analyzed by flow-injection analysis coupled to tandem mass spectrometry or gas chromatography coupled with mass spectrometry. Kruskal Wallis rank tests and Cox regressions were used to analyze the association of lipids with CKD severity and the risk of combined outcome, respectively. RESULTS: The plasma level of PCs, LPCs, and SMs was decreased in HD patients compared with nondialyzed CKD patients (all P < .05), whereas esterified and/or nonesterified fatty acids level did not change. Thirty-four lipids displayed significantly lower abundance in plasma of HD patients, whereas elaidic acid (C18:1ω9t) level was increased (P < .001). The total amount of LPCs and individual LPCs were associated with better outcome (P < .05). In particular, LPC 18:2 and LPC 20:3 were statistically associated with outcome in adjusted models (P < .05). DISCUSSION: In HD patients, a reduction in plasma lipids is observed. Some of the alterations, namely reduced LPCs, were associated with the risk of adverse outcome. These changes could be related to metabolic dysfunctions.

Correction: Consequences of increasing convection onto patient care and protein removal in hemodialysis.

[This corrects the article DOI: 10.1371/journal.pone.0171179.].

Geographical Variations in Blood Pressure Level and Seasonality in Hemodialysis Patients.

Seasons and climate influence the regulation of blood pressure (BP) in the general population and in hemodialysis patients. It is unknown whether this phenomenon varies across the world. Our objective was to estimate BP seasonality in hemodialysis patients from different geographical locations. Patients from 7 European countries (Spain, Italy, France, Belgium, Germany, United Kingdom, and Sweden) participating in the DOPPS (Dialysis Outcomes and Practice Patterns Study) on years 2005 to 2011 were studied. Factors influencing pre- and postdialysis systolic BP and diastolic BP levels were analyzed by mixed models. There were 9655 patients (median age, 68; 59% male) from 263 facilities, seen every 4 months during a median duration of 1.3 years. Pre- and postdialysis systolic BP increased by a mean estimate of 5.1 mm Hg (95% confidence interval [CI], 3.7-6.4 mm Hg) and 4.4 mm Hg (95% CI, 2.9-5.9 mm Hg) for each 10° increase in latitude (1111 km to the North). In the longitudinal analysis, predialysis systolic BP was lower in summer and higher in winter (difference, 1.7 mm Hg; 95% CI, 1.3-2.2 mm Hg), with greater differences in southern locations (Pinteraction=0.04). Predialysis systolic BP was inversely associated with outdoor temperature (-0.8 mm Hg/7.2°C; 95% CI, -1.0 to -0.5 mm Hg/7.2°C), with steeper slopes in southern locations (Pinteraction=0.005). Results were similar for predialysis diastolic BP. In conclusion, there is a geographical and seasonal gradient of BP in European hemodialysis patients. There is a need to consider these effects when evaluating and treating BP in this population and potentially in others.

Consequences of increasing convection onto patient care and protein removal in hemodialysis.

INTRODUCTION: Recent randomised controlled trials suggest that on-line hemodiafiltration (OL-HDF) improves survival, provided that it reaches high convective volumes. However, there is scant information on the feasibility and the consequences of modifying convection volumes in clinics. METHODS: Twelve stable dialysis patients were treated with high-flux 1.8 m2 polysulphone dialyzers and 4 levels of convection flows (QUF) based on GKD-UF monitoring of the system, for 1 week each. The consequences on dialysis delivery (transmembrane pressure (TMP), number of alarms, % of achieved prescribed convection) and efficacy (mass removal of low and high molecular weight compounds) were analysed. RESULTS: TMP increased exponentially with QUF (p<0.001 for N >56,000 monitoring values). Beyond 21 L/session, this resulted into frequent TMP alarms requiring nursing staff interventions (mean ± SEM: 10.3 ± 2.2 alarms per session, p<0.001 compared to lower convection volumes). Optimal convection volumes as assessed by GKD-UF-max were 20.6 ± 0.4 L/session, whilst 4 supplementary litres were obtained in the maximum situation (24.5 ± 0.6 L/session) but the proportion of sessions achieving the prescribed convection volume decreased from 94% to only 33% (p<0.001). Convection increased high molecular weight compound removal and shifted the membrane cut-off towards the higher molecular weight range. CONCLUSIONS: Reaching high convection volumes as recommended by the recent RCTs (> 20L) is feasible by setting an HDF system at its optimal conditions based upon the GKD-UF monitoring. Prescribing higher convection volumes resulted in instability of the system, provoked alarms, was bothersome for the nursing staff and the patients, rarely achieved the prescribed convection volumes and increased removal of high molecular weight compounds, notably albumin.

Early changes in body weight and blood pressure are associated with mortality in incident dialysis patients.

BACKGROUND: While much research is devoted to identifying novel biomarkers, addressing the prognostic value of routinely measured clinical parameters is of great interest. We studied early blood pressure (BP) and body weight (BW) trajectories in incident haemodialysis patients and their association with all-cause mortality. METHODS: In a cohort of 357 incident patients, we obtained all records of BP and BW during the first 90 days on dialysis (over 12 800 observations) and analysed trajectories using penalized B-splines and mixed linear regression models. Baseline comorbidities and all-cause mortality (median follow-up: 2.2 years) were obtained from the French Renal Epidemiology and Information Network (REIN) registry, and the association with mortality was assessed by Cox models adjusting for baseline comorbidities. RESULTS: During the initial 90 days on dialysis, there were non-linear decreases in BP and BW, with milder slopes after 15 days [systolic BP (SBP)] or 30 days [diastolic BP (DBP) and BW]. SBP or DBP levels at dialysis initiation and changes in BW occurring in the first month or during the following 2 months were significantly associated with survival. In multivariate models adjusting for baseline comorbidities and prescriptions, higher SBP value and BW slopes were independently associated with a lower risk of mortality. Hazard ratios of mortality and 95% confidence intervals were 0.92 (0.85-0.99) for a 10 mmHg higher SBP and 0.76 (0.66-0.88) for a 1 kg/month higher BW change on Days 30-90. CONCLUSIONS: BW loss in the first weeks on dialysis is a strong and independent predictor of mortality. Low BP is also associated with mortality and is probably the consequence of underlying cardiovascular diseases. These early markers appear to be valuable prognostic factors.

Seasonal modifications in blood pressure are mainly related to interdialytic body weight gain in dialysis patients.

BACKGROUND: Longitudinal studies in dialysis patients have identified seasonal variations in blood pressure that may follow climatic parameters such as external temperature and humidity. We aimed to assess the participation of interdialytic body weight gain variations in the seasonal profile of blood pressure. METHODS: Ninety-nine stable patients (40 F/59 M), 52.9 +/- 1.5 years old, dialyzed in a single satellite dialysis unit between January 7, 1991, and September 30, 1998 were studied. Supine systolic and diastolic blood pressure, body weight, and interdialytic body weight gain were determined at every one of the 38,769 dialyses included, and studied along with climatology data obtained from Météo, France. RESULTS: Blood pressure varied throughout the year, following a cyclic pattern. It increased from the autumn months toward winter, and decreased toward the spring and warmer months. Systolic and diastolic blood pressures were strongly correlated with interdialytic body weight gain (r= 0.925; P < 0.0001 and r= 0.888; P= 0.0001, respectively). Blood pressure was also correlated with the climatic factors: rainfall (r= 0.786; P < 0.003 and r= 0.784; P < 0.003), humidity (r= 0.701; P= 0.011 and r= 0.699; P < 0.012), and day light span (r=-0712; P < 0.01, and r=-0.658; P < 0.02, respectively). Multivariate regression analyses taking blood pressure as a dependent variable retained interdialytic body weight gain as the first variable in the model. CONCLUSION: Our results establish a strong link between blood pressure variations and interdialytic body weight gain, showing the important participation of volume state in modulating blood pressure in this group of patients.

Blood pressure is correlated with vitamin d(3) serum levels in dialysis patients.

BACKGROUND/AIMS: The blood pressure, the most influencing factor in cardiovascular disease in end-stage renal failure patients, follows a seasonal variation during the year. Since vitamin D(3) is known to be related to sun exposure, we wanted to evaluate the putative participation of the vitamin D(3) metabolism in blood pressure modifications. METHODS: We studied 22 stable hemodialysis patients (11 females and 11 males, mean age +/- SD 56 +/- 1 year) who had been continuously treated in our dialysis unit for more than 1 year between 1994 and 1997 and did not receive pulse vitamin D(3) treatment. Supine systolic and diastolic blood pressures were measured before every dialysis session (>12,000 measurements) and the intact parathormone (iPTH), 25-hydroxyvitamin D(3) [25(OH)D(3)], and 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] levels every 3 months (>300 determinations). The mean values of blood pressure per season and per patient were taken for analysis using a 4-year longitudinal study design. RESULTS: The blood pressure varied during the years studied following a seasonal trend. It was highest during autumn and tended to decrease during spring and warmer months. Systolic as well as diastolic blood pressures were significantly correlated with the 25(OH)D(3) levels (p = 0.0291 and p = 0.0327, respectively). No correlation was observed between blood pressure and 1,25(OH)(2)D(3) or iPTH levels. CONCLUSION: There is a link between blood pressure and 25(OH)D(3) level. This interrelation is not secondary to a iPTH modulation. Although it cannot be excluded that vitamin D(3) and blood pressure vary following a third factor with seasonal variations, since vitamin D(3) varies during the year, mainly following sun exposure, we suggest that vitamin D(3) is one of the factors participating in the seasonal variation of the blood pressure. Other factors known to control the blood pressure and particularly the extracellular volume overload may also participate.