HAEMODIALYSIS TECHNIQUES AND ADEQUACY 1

Abstract

Introduction and Aims: Different types of cells have been used for the development of potential bioartificial kidney devices. Recently, the reprogramming of adult cells to embryonic nephron progenitors (C.E.Hendry et al JASN 2013) and human embryonic stem cells differentiated to renal proximal tubular cells (K.Narayan et al KI 2013) have been used as potential building blocks for a bioartificial kidney. Here we propose the combination of adult renal progenitor/stem cells with different microfabrication and nanofabrication technologies to develop miniaturized, bioartificial proximal tubule-like platforms, which are very promising tools for next-generation bio-analytic assays and for studying the nephrotoxicity of drugs. The potentialities of these interdisciplinary, cross-cutting platforms for in-vitro testing of drugs are presented and discussed. Methods: Our class of devices is composed of overlapped elastomeric layers, embedding microfluidic connections, porous and functionalized membranes, and polymeric valves, as well as suitable pumps to control all the involved flows, besides living cells. All the tested experimental geometries are designed and realized to mimic the in vivo kidney structures, and specifically renal tubules. Employed microtechnologies include optical and soft lithography, and particular care is paid to ensure the biocompatibility of all the involved device surfaces. In the devices, living cells are placed in contact with functionalized membranes to tailor and control the transport of solutes. Results: The basement membrane of tubules is composed by several extracellular matrix proteins, we generally find that fibronectin promoted an enhanced proliferation of stem cells compared to other proteins. Various kinds of renal cells were used to test our devices. Then, the culture conditions and initial seeding concentration on-chip were optimized up to reaching confluence of cells. Working conditions, operating fluxes as well as fluidic connections were optimized to obtain functional bio-chips with polarized ARPCs. Solute transport across membranes was studied in detail, and found to be modulated by the embedded cells up to permeability values of the order of 0.5 {micro}m/s. Conclusions: Bioartificial proximal-tubule like device platforms represent an interesting model for studying the nephrotoxicity of drugs by microfluidic approaches. The combination of cross-cutting technologies derived from complementary disciplines will certainly constitute a strategic pathway to implement novel bio-assays of remarkable nephrologic interest in the near future. Introduction and Aims: Based on empirical observations, we hypothesized that less frequent Haemodialysis (HD) could preserve residual renal function (RRF). Accordingly, for decades, we have been trying to start maintenance HD on once-weekly schedule in almost every patient with significant RRF, soon increasing the frequency of treatment in the case of deterioration of RRF and Urinary Output (UO) or clinical status. More recently we have decided to start all new patients on once-weekly predilution HDF or HF. The aim of this study was to evaluate the impact of different initial dialysis schedules and/or modalities on RRF survival. Methods: We retrieved data of all ESRD patients started on HD at our Unit from January, 2000 to June, 2013, and followed-up for at least 6 months. The patients were divided into 3 groups (G), based on the initial schedule (the one present 2 months after the start) and/or modality of treatment: standard HD, 3 sessions per week (3HD/w, G1); HD once or twice weekly, (1HD/w, G2), and pre-dilution HDF or HF once weekly (1HDF/w, G3). For the sake of simplicity, 500 mL/day was arbitrarily set as the critical level of UO, so that, the RRF survival time, to be used with Kaplan-Meyer (KM) analysis, was computed as the time interval between the date of the 1st dialysis and that of the last measured UO equal or greater than 500 mL/day. Results: We found a total of 150 patients fulfilling the inclusion criteria. As shown in table 1, the main baseline patients' characteristics were similar for the 3 groups. The KM analysis showed a significant (Log Rank, p<0.001) difference among groups, with an impressive 2-year cumulative RRF survival of 89% for G3, vs 27% for G1, and 63% for G2 patients. The 3-year survival rate for G3 patients remained stable at 89%. Conclusions: Due to the observational nature of the study, the above results only suggest that starting HD on a less frequent schedule could allow a long RRF survival time, further prolonged by using HDF or HF. Interestingly, similar data showing a beneficial effect of twice-weekly HD on RRF survival have recently been published for a large group of Chineese patients. Such an effect is usually explained by less hypotensive episodes on 2HD/w vs 3HD/w patients. However, it is also possible that less frequent dialysis could be more biocompatible. Moreover, the associated higher BUN levels could maintain a beneficial osmotic diuresis. A soft HDF or HF, using low volume flows, ultrapure diialysate and very compatible membranes, would both avoid too low BUN levels and increase biocompatibility. While waiting for evidence-based new guide lines for dialysis start, we believe that everyone could safely test our approach by starting a few suitable patients on 1HDF or HF/w, being careful to increase the frequency on the basis of the observed GFR and UO (or interdialysis weight gain) values as well as clinical status, paying a particular attention to the control of biochemistries, ECF volume and blood pressure. We would stress that using the UKM-based incremental approach is not recommended because, due to the the erroneous assumption of equivalency between renal and dialytic clearance, it overestimates the dialysis needs, so that 1 HD/w would be nearly impossible. Moreover, as hypothesised above, a high efficient treatment could increase the RRF loss rate. View this table: SP4112C63BA5BE3FE846C4BB16DE34FDA73D4C500400SP4112C63BA5BE3FE846C4BB16DE34FDA73D4C Baseline patients characteristics and RRF survival by group Introduction and Aims: Online hemodiafiltration (HDF) with high-volume substitution fluid is an optimal way to remove uremic substances ranging widely in molecular size from small to low molecular weight (MW). Post-dilution HDF is the most efficient infusion mode to obtain maximum clearance.Mid-dilution infusion is an interesting alternative that represents simultaneous pre- and post- dilution infusion modes and could be a highly effective technique to remove uremic toxins, avoiding the disadvantages of pre- and post-dilutional modes.The aim of this multicentric study was to compare mid-dilution (MID) with post-dilution HDF (POST) by evaluating their efficiency in removing different middle MW (MMW) and protein bound uremic toxins. Methods: We performed a cross-over study including 158 Patients from 21 centres. All patients were randomized in two different groups for three months: group A (1 month MID - 1 month POST -1 month MID) and group B (1 month POST- 1 month MID -1 month POST). 64 patients were excluded from the final analysis because of incomplete data. The reduction rate (RR) of middle and protein bound molecules were centrally determined from serum samples as well as the second generation Daugirdas Kt/Vd. Albumin loss was carried out for both groups.Unpaired t student test was performed using GraphPad prism version 4.00 for Windows. Results: The data of 94 (48 from group A and 46 from group B) patients (53M and 41F) were fully analysed. The median age was 70 (27-92) years and dialysis vintage was 47,2 (7,5/454,6) months. No difference was found in the demographic characteristics and treatment parameters. 164 MID sessions and 161 POST sessions were analysed. A statistically significant difference in RR (%) was found for three MMW molecules: {beta}-2 Microglobulin ({beta}2M), Complement Factor D (CFD) and Retinol Binding protein (RBP). Values were 80,1{+/-}0,4 in POST vs 81,6{+/-}0,4 in MID (p=0,01) for {beta}2M; 72,8{+/-}0,8 in POST vs 76,4{+/-}0,6 in MID (p=0,0003) for CFD and 24,1{+/-}0,9 in POST vs 30,0{+/-}0,8 in MID (p=0,003) for RBPThe other investigated molecules, ADMA, Homocystein, Leptin and Myoglobin, shown a better MID RR but it is not statistically significant.The reinfused volume was significantly higher in MID than in POST (average total volume of 43,63 L in MID vs 20,96 L in POST), but also the amount of reinfused volume in MID exchanged in its post dilution stage (estimated around the 2/3 as shown in Maduell publication) is significantly higher (28,8 L in MID vs 20,96 L in POST); this could explain the depuration capability of MID respect POST for the MMW molecules, indeed, was found a linear correlation (R2 0.83) between the delta differences in RR (RR Mid - RR Post) and MW of molecules (Figure 1). No significant differences between MID - and POST-dilution were observed for small MW molecules depuration (assessed by second generation daugirdas Kt/vd), neither for Albumin loss. SP4122C6C2D3E6CB004D7C91C266ECD9EF52CB"> WIDTH=200 HEIGHT=124 SRC="/small/SP412_2_C6C2D3E6-CB00-4D7C-91C2-66ECD9EF52CB.gif" ALT="Figure 52CB"> View larger version (16K): SP4122C6C2D3E6CB004D7C91C266ECD9EF52CB590473SP4122C6C2D3E6CB004D7C91C266ECD9EF52CB Conclusions: MID is superior to remove MMW molecules as compared to POST. This very likely can be related to an higher total amount and efficiency of substituted volume obtained in the MID group as compared to the POST group. Introduction and Aims: Attention to the environmental impact is still limited in medicine. Chronic Hemodialysis produces about 600000 tons of plastic wastes per year. The economic crisis and the awareness of the ecosystem induced to focus attention on the lifespan of disposables,"from cradle to grave". A new outlook is presently focussed on recycle, that is the subsequent start of new cycles leading to a "from cradle to cra