@phdthesis{Hackl2011,
  author    = {Hackl, Andrea},
  title     = {Einfluss von Dialyseverfahren und Dialysemembranpermeabilit{\"a}t auf die Entfernung von Ur{\"a}mietoxinen},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-57593},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2011},
  abstract  = {Im Vergleich zur Normalbev{\"o}lkerung ist die Morbidit{\"a}t und Mortalit{\"a}t chronisch h{\"a}modialysepflichtiger Patienten signifikant erh{\"o}ht. Daher wird intensiv an der Optimierung der Nierenersatztherapie einschließlich der Effizienzsteigerung der Dialysemembranen gearbeitet. PUREMA® H ist eine innovative synthetische High-Flux-Membran, die in Form der durchl{\"a}ssigeren PUREMA® H+ nochmals weiterentwickelt wurde. In der vorliegenden Untersuchung wurde ein klinischer Vergleich der PUREMA® H- und H+-Membranen sowohl im HD-, als auch im HDF- Verfahren hinsichtlich der Elimination von Ur{\"a}mietoxinen in Abh{\"a}ngigkeit von der Permeabilit{\"a}t der Membranen f{\"u}r Albumin angestellt. In einer prospektiven, randomisierten „Cross-over-Studie" an acht chronisch dialysepflichtigen Patienten wurde die Behandlungseffizienz anhand von Plasmaclearances, Reduktionsraten und Dialysatmassentransfer von kleinmolekulargewichtigen Proteinen, sowie proteingebundenen Toxinen gemessen. Weder f{\"u}r die kleinmolekularen Substanzen Harnstoff, Kreatinin und Phosphat noch f{\"u}r die mittelmolekularen Marker b2m und Cystatin C ließen sich in HD und HDF Unterschiede zwischen den beiden Membranen ermitteln. Lediglich hinsichtlich der Reduktionsraten der gr{\"o}ßeren Substanzen Myoglobin und Retinol-bindendem Protein wurden im HD-Verfahren mit PUREMA® H+ signifikant bessere Ergebnisse erzielt..Dagegen ließ sich die {\"U}berlegenheit von HDF gegen{\"u}ber HD im Bereich der mittelmolekularen und gr{\"o}ßeren Proteine durchgehend nachweisen. So lagen die Clearances f{\"u}r b2m in HDF im Schnitt 52\% {\"u}ber den im HD-Verfahren ermittelten Werten. Bez{\"u}glich der proteingebundenen Toxine konnte weder zwischen den Membranen, noch zwischen HD und HDF ein signifikanter Unterschied in der Entfernung nachgewiesen werden. Die Reduktionsraten f{\"u}r die proteingebundenen Anteile von pCs betrugen zwischen ca.,40 und 48\%, bei Indoxylsulfat lagen sie zwischen 50 und 55\%. Interessanterweise fand sich ein hochgradiger direkter positiver Zusammenhang zwischen der Konzentration von pCs und IS im Plasma vor der Behandlung und der entfernten Masse der freien Fraktion im Dialysat. Der Albuminverlust ins Dialysat war bei PUREMA® H+ in beiden Verfahren signifikant gr{\"o}ßer als bei PUREMA® H, betrug jedoch maximal 1,4 g (PUREMA® H+ in HDF). Eine derartige Gr{\"o}ßenordnung ist klinisch als sehr gering einzustufen, so dass die Albuminpermeabilit{\"a}t von PUREMA® H+ noch gesteigert werden k{\"o}nnte, um damit {\"u}ber eine konsekutive Erh{\"o}hung der internen Filtration ggf. eine Verbesserung der konvektiven Entfernung von kleinmolekulargewichtigen Ur{\"a}mietoxinen herbeizuf{\"u}hren. Ob eine Steigerung der Porengr{\"o}ße auch zu einer effizienteren Elimination von proteingebundenen Ur{\"a}mietoxinen f{\"u}hrt, d{\"u}rfte jedoch h{\"o}chst fraglich sein, da die Ergebnisse der vorliegenden Untersuchung im Gegensatz zu Diffusion nur f{\"u}r eine unbedeutende Rolle von Konvektion bei der Entfernung dieser Substanzen sprechen. Diesbez{\"u}glich sind alternative, z.B. adsorptive Behandlungsstrategien m{\"o}glicherweise vielversprechender.},
  subject      = {Dialyse},
  language  = {de}
}
@article{DevineKrieterRuethetal.2014,
  author    = {Devine, Eric and Krieter, Detlef H. and R{\"u}th, Marieke and Jankovski, Joachim and Lemke, Horst-Dieter},
  title     = {Binding Affinity and Capacity for the Uremic Toxin Indoxyl Sulfate},
  series = {Toxins},
  volume    = {6},
  journal   = {Toxins},
  number    = {2},
  doi       = {10.3390/toxins6020416},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-117486},
  pages     = {416-429},
  year      = {2014},
  abstract  = {Protein binding prevents uremic toxins from removal by conventional extracorporeal therapies leading to accumulation in maintenance dialysis patients. Weakening of the protein binding may enhance the dialytic elimination of these toxins. In ultrafiltration and equilibrium dialysis experiments, different measures to modify the plasma binding affinity and capacity were tested: (i), increasing the sodium chloride (NaCl) concentration to achieve a higher ionic strength; (ii), increasing the temperature; and (iii), dilution. The effects on the dissociation constant K-D and the protein bound fraction of the prototypical uremic toxin indoxyl sulfate (IS) in plasma of healthy and uremic individuals were studied. Binding of IS corresponded to one site binding in normal plasma. K-D increased linearly with the NaCl concentration between 0.15 (K-D = 13.2 +/- 3.7 mu M) and 0.75 M (K-D = 56.2 +/- 2.0 mu M). Plasma dilution further reduced the protein bound toxin fraction by lowering the protein binding capacity of the plasma. Higher temperatures also decreased the protein bound fraction of IS in human plasma. Increasing the NaCl concentration was effective to weaken the binding of IS also in uremic plasma: the protein bound fraction decreased from 89\% +/- 3\% to 81\% +/- 3\% at 0.15 and 0.75 M NaCl, respectively. Dilution and increasing the ionic strength and temperature enhance the free fraction of IS allowing better removal of the substance during dialysis. Applied during clinical dialysis, this may have beneficial effects on the long-term outcome of maintenance dialysis patients.},
  language  = {en}
}
@phdthesis{Devine2013,
  author    = {Devine, Eric},
  title     = {Increased removal of protein bound uremic toxins through reversible modification of the ionic strength during hemodiafiltration},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-83583},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {A large number of metabolic waste products accumulate in the blood of patients with renal failure. Since these solutes have deleterious effects on the biological functions, they are called uremic toxins and have been classified in three groups: 1) small water soluble solutes (MW < 500 Da), 2) small solutes with known protein binding (MW < 500 Da), and 3) middle molecules (500 Da < MW < 60 kDa). Protein bound uremic toxins are poorly removed by conventional hemodialysis treatments because of their high protein binding and high distribution volume. The prototypical protein bound uremic toxins indoxyl sulfate (IS) and p-cresyl sulfate (pCS) are associated with the progression of chronic kidney disease, cardiovascular outcomes, and mortality of patients on maintenance hemodialysis. Furthermore, these two compounds are bound to albumin, the main plasma protein, via electrostatic and/or Van-der-Waals forces. The aim of the present thesis was to develop a dialysis strategy, based on the reversible modification of the ionic strength in the blood stream by increasing the sodium chloride (NaCl) concentration, in order to enhance the removal of protein bound substances, such as IS and pCS, with the ultimate goal to improve clinical patient outcomes. Enhancing the NaCl concentration ([NaCl]) in both human normal and uremic plasma was efficient to reduce the protein bound fraction of both IS and pCS by reducing their binding affinity to albumin. Increasing the ionic strength was feasible during modified pre-dilution hemodiafiltration (HDF) by increasing the [NaCl] in the substitution fluid. The NaCl excess was adequately removed within the hemodialyzer. This method was effective to increase the removal rate of both protein bound uremic toxins. Its ex vivo hemocompatibility, however, was limited by the osmotic shock induced by the high [NaCl] in the substituate. Therefore, modified pre-dilution HDF was further iterated by introducing a second serial cartridge, named the serial dialyzers (SDial) setup. This setting was validated for feasibility, hemocompatibility, and toxin removal efficiency. A better hemocompatibility at similar efficacy was obtained with the SDial setup compared with the modified pre-dilution HDF. Both methods were finally tested in an animal sheep model of dialysis to verify biocompatibility. Low hemolysis and no activation of both the complement and the coagulation systems were observed when increasing the [NaCl] in blood up to 0.45 and 0.60 M with the modified pre-dilution HDF and the SDial setup, respectively. In conclusion, the two dialysis methods developed to transitory enhance the ionic strength in blood demonstrated adequate biocompatibility and improved the removal of protein bound uremic toxins by decreasing their protein bound fraction. The concepts require follow-on clinical trials to assess their in vivo efficacy and their impact on long-term clinical outcomes.},
  subject      = {H{\"a}modiafiltration},
  language  = {en}
}