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 (B_i), blood outlet (B_o) and dialysate outlet (D_o) were continuously recorded. TMP was calculated using two pressures (TMP2: B_o, D_o) or three pressures (TMP3: B_o, D_o, B_i). 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 B_i 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.

Mechanisms of tissue factor induction by the uremic toxin indole-3 acetic acid through aryl hydrocarbon receptor/nuclear factor-kappa B signaling pathway in human endothelial cells

Chronic kidney disease (CKD) is associated with high risk of thrombosis. Indole-3 acetic acid (IAA), an indolic uremic toxin, induces the expression of tissue factor (TF) in human umbilical vein endothelial cells (HUVEC) via the transcription factor aryl hydrocarbon receptor (AhR). This study aimed to understand the signaling pathways involved in AhR-mediated TF induction by IAA. We incubated human endothelial cells with IAA at 50 µM, the maximal concentration found in patients with CKD. IAA induced TF expression in different types of human endothelial cells: umbilical vein (HUVEC), aortic (HAoEC), and cardiac-derived microvascular (HMVEC-C). Using AhR inhibition and chromatin immunoprecipitation experiments, we showed that TF induction by IAA in HUVEC was controlled by AhR and that AhR did not bind to the TF promoter. The analysis of TF promoter activity using luciferase reporter plasmids showed that the NF-κB site was essential in TF induction by IAA. In addition, TF induction by IAA was drastically decreased by an inhibitor of the NF-κB pathway. IAA induced the nuclear translocation of NF-κB p50 subunit, which was decreased by AhR and p38MAPK inhibition. Finally, in a cohort of 92 CKD patients on hemodialysis, circulating TF was independently related to serum IAA in multivariate analysis. In conclusion, TF up-regulation by IAA in human endothelial cells involves a non-genomic AhR/p38 MAPK/NF-κB pathway. The understanding of signal transduction pathways related to AhR thrombotic/inflammatory pathway is of interest to find therapeutic targets to reduce TF expression and thrombotic risk in patients with CKD.

Performance of an easy-to-use prediction model for renal patient survival: an external validation study using data from the ERA-EDTA Registry

Background

An easy-to-use prediction model for long-term renal patient survival based on only four predictors [age, primary renal disease, sex and therapy at 90 days after the start of renal replacement therapy (RRT)] has been developed in The Netherlands. To assess the usability of this model for use in Europe, we externally validated the model in 10 European countries.

Methods

Data from the European Renal Association-European Dialysis and Transplant Association (ERA-EDTA) Registry were used. Ten countries that reported individual patient data to the registry on patients starting RRT in the period 1995-2005 were included. Patients <16  years of age and/or with missing predictor variable data were excluded. The external validation of the prediction model was evaluated for the 10- (primary endpoint), 5- and 3-year survival predictions by assessing the calibration and discrimination outcomes.

Results

We used a data set of 136 304 patients from 10 countries. The calibration in the large and calibration plots for 10 deciles of predicted survival probabilities showed average differences of 1.5, 3.2 and 3.4% in observed versus predicted 10-, 5- and 3-year survival, with some small variation on the country level. The concordance index, indicating the discriminatory power of the model, was 0.71 in the complete ERA-EDTA Registry cohort and varied according to country level between 0.70 and 0.75.

Conclusions

A prediction model for long-term renal patient survival developed in a single country, based on only four easily available variables, has a comparably adequate performance in a wide range of other European countries.

[Treatment of chronic kidney failure by haemodialysis]

Haemodialysis is the most frequently used renal replacement therapy for chronic kidney disease. Much progress has been made in this field since the invention of this technique. The nurse nevertheless continues to play an essential role. Kidney transplantation is gradually becoming the first-line treatment, the aim of dialysis being to prepare patients for this procedure.

End-stage renal disease treated in Provence-Alpes Côte d'Azur: 12-years follow-up and forecast to the year 2030

BACKGROUND

This study describes the time trend of renal replacement therapy for end-stage renal disease (ESRD) in the Provence-Alpes Côte d'Azur region (PACA) between 2004 and 2015, and forecasts up to 2030.

METHODS

A longitudinal study was conducted on all ESRD patients treated in PACA and recorded in the French Renal Epidemiology and Information Network (REIN) during this period. Time trends and forecasts to 2030 were analyzed using Poisson regression models.

RESULTS

Since 2004, the number of new patients has steadily increased by 3.4% per year (95% CI, 2.8-3.9, p < 0.001) and the number of patients receiving RRT has increased by 3.7% per year (RR 1.037, 95% CI: 1.034-1.039, p < 0.001). If these trends continue, the PACA region will be face with 7371 patients on dialysis and 3891 with a functional renal transplant who will need to be managed in 2030. The two most significant growth rates were the percentage of obese people (RR 1.140, 95% CI: 1.131-1.149, p < 0.001) and those with diabetes (RR 1.070, 95% CI; 1.064-1.075, p < 0.001).

CONCLUSION

This study highlights the increase in the number of ESRD patients over 12 years, with no prospect of stabilization. These findings allow us to anticipate the quality and quantity of care offered and to propose more preventive measures to combat obesity and diabetes.

Drop spreading and gelation of thermoresponsive polymers

Spreading and solidification of liquid droplets are elementary processes of relevance for additive manufacturing. Here we investigate the effect of heat transfer on spreading of a thermoresponsive solution (Pluronic F127) that undergoes a sol-gel transition above a critical temperature Tm. By controlling the concentration of Pluronic F127 we systematically vary Tm, while also imposing a broad range of temperatures of the solid and the liquid. We subsequently monitor the spreading dynamics over several orders of magnitude in time and determine when solidification stops the spreading. It is found that the main parameter is the difference between the substrate temperature and Tm, pointing to a local mechanism for arrest near the contact line. Unexpectedly, the spreading is also found to stop below the gelation temperature, which we attribute to a local enhancement in polymer concentration due to evaporation near the contact line.

Neuraxial analgesia is not associated with an increased risk of post-partum relapses in MS

Background:

Obstetrical analgesia remains a matter of controversy because of the fear of neurotoxicity of local anesthetics on demyelinated fibers or their potential relationship with subsequent relapses.

Objective:

To assess the impact of neuraxial analgesia on the risk of relapse during the first 3 months post-partum, with a focus on women who experienced relapses during pregnancy.

Methods:

We analyzed data of women followed-up prospectively during their pregnancies and at least 3 months post-partum, collected in the Pregnancy in Multiple Sclerosis (PRIMS) and Prevention of Post-Partum Relapses with Progestin and Estradiol in Multiple Sclerosis (POPARTMUS) studies between 1992–1995 and 2005–2012, respectively. The association of neuraxial analgesia with the occurrence of a post-partum relapse was estimated by logistic regression analysis.

Results:

A total of 389 women were included, 215 from PRIMS and 174 from POPARTMUS. In total, 156 women (40%) had neuraxial analgesia. Overall, 24% experienced a relapse during pregnancy and 25% in the 3 months post-partum. Women with a pregnancy relapse were more likely to have a post-partum relapse (odds ratio (OR) = 1.83, p = 0.02), independently of the use of neuraxial analgesia. There was no association between neuraxial analgesia and post-partum relapse (OR = 1.08, p = 0.78).

Conclusion:

Neuraxial analgesia was not associated with an increased risk of post-partum relapses, whatever multiple sclerosis (MS) activity during pregnancy.

In Vivo Accumulation of Sodium Pump Inhibitor by Normal and Uremic Erythrocytes

A uremic toxin fraction (fraction 2-3-1) in the middle molecular mass range (300-2000 Da) containing a sodium potassium inhibitor pump was studied. As fraction 2-3-1 was known to be present in minute quantities in urine and plasma, erythrocyte lysates were used as an alternative source. Results show that fraction 2-3-1 is more abundant in erythrocytes than in normal urine. In addition, the fraction is present in a greater quantity in uremic erythrocytes than in normal blood cells. It is concluded that fraction 2-3-1 is concentrated at the erythrocyte level in uremic patients

Uremic Toxicity: Present State of the Art

The uremic syndrome is a complex mixture of organ dysfunctions, which is attributed to the retention of a myriad of compounds that under normal condition are excreted by the healthy kidneys (uremic toxins). In the area of identification and characterization of uremic toxins and in the knowledge of their pathophysiologic importance, major steps forward have been made during recent years. The present article is a review of several of these steps, especially in the area of information about the compounds that could play a role in the development of cardiovascular complications. It is written by those members of the Uremic Toxins Group, which has been created by the European Society for Artificial Organs (ESAO). Each of the 16 authors has written a state of the art in his/her major area of interest.

Aryl hydrocarbon receptor is activated in patients and mice with chronic kidney disease

Patients with chronic kidney disease (CKD) are exposed to uremic toxins and have an increased risk of cardiovascular disease. Some uremic toxins, like indoxyl sulfate, are agonists of the transcription factor aryl hydrocarbon receptor (AHR). These toxins induce a vascular procoagulant phenotype. Here we investigated AHR activation in patients with CKD and in a murine model of CKD. We performed a prospective study in 116 patients with CKD stage 3 to 5D and measured the AHR-Activating Potential of serum by bioassay. Compared to sera from healthy controls, sera from CKD patients displayed a strong AHR-Activating Potential; strongly correlated with eGFR and with the indoxyl sulfate concentration. The expression of the AHR target genes Cyp1A1 and AHRR was up-regulated in whole blood from patients with CKD. Survival analyses revealed that cardiovascular events were more frequent in CKD patients with an AHR-Activating Potential above the median. In mice with 5/6 nephrectomy, there was an increased serum AHR-Activating Potential, and an induction of Cyp1a1 mRNA in the aorta and heart, absent in AhR^-/- CKD mice. After serial indoxyl sulfate injections, we observed an increase in serum AHR-AP and in expression of Cyp1a1 mRNA in aorta and heart in WT mice, but not in AhR^-/- mice. Thus, the AHR pathway is activated both in patients and mice with CKD. Hence, AHR activation could be a key mechanism involved in the deleterious cardiovascular effects observed in CKD.

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

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

Indoxyl Sulfate Upregulates Liver P-Glycoprotein Expression and Activity through Aryl Hydrocarbon Receptor Signaling

In patients with CKD, not only renal but also, nonrenal clearance of drugs is altered. Uremic toxins could modify the expression and/or activity of drug transporters in the liver. We tested whether the uremic toxin indoxyl sulfate (IS), an endogenous ligand of the transcription factor aryl hydrocarbon receptor, could change the expression of the following liver transporters involved in drug clearance: SLC10A1, SLC22A1, SLC22A7, SLC47A1, SLCO1B1, SLCO1B3, SLCO2B1, ABCB1, ABCB11, ABCC2, ABCC3, ABCC4, ABCC6, and ABCG2 We showed that IS increases the expression and activity of the efflux transporter P-glycoprotein (P-gp) encoded by ABCB1 in human hepatoma cells (HepG2) without modifying the expression of the other transporters. This effect depended on the aryl hydrocarbon receptor pathway. Presence of human albumin at physiologic concentration in the culture medium did not abolish the effect of IS. In two mouse models of CKD, the decline in renal function associated with the accumulation of IS in serum and the specific upregulation of Abcb1a in the liver. Additionally, among 109 heart or kidney transplant recipients with CKD, those with higher serum levels of IS needed higher doses of cyclosporin, a P-gp substrate, to obtain the cyclosporin target blood concentration. This need associated with serum levels of IS independent of renal function. These findings suggest that increased activity of P-gp could be responsible for increased hepatic cyclosporin clearance. Altogether, these results suggest that uremic toxins, such as IS, through effects on drug transporters, may modify the nonrenal clearance of drugs in patients with CKD.

Soluble CD146, a novel endothelial marker, is increased in physiopathological settings linked to endothelial junctional alteration

CD146, a novel cell adhesion molecule localized at the endothelial junction, is involved in the control of cell-cell cohesion. It is found as a soluble form in conditioned medium of cultured endothelial cells. We developed an ELISA and report for the first time the presence of a soluble form of CD146 (sCD146) in the plasma of healthy subjects. Mean sCD146 values (260 ± 60 ng/ml) were higher in subjects over 50 years and in men. We therefore investigated sCD146 values in patients with chronic renal failure (CRF), a clinical setting associated with junctional alterations. A significant increase in sCD146 was found in patients with CRF matched with controls (457 ± 181 ng/ml versus 288 ± 82 ng/ml respectively, p<0.0001). This increase was corroborated by increased endothelial expression of CD146 on kidney biopsies from patients with CRF. In contrast, in patients with CRF no modulation was observed for the soluble and cell-associated form of CD31, another junctional molecule. Together these data indicate that sCD146 circulates in the plasma of healthy subjects. Modifications of its basal levels could reflect alterations of junctional functions such as vascular permeability.