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Therapeutic Apheresis and Dialysis :... Apr 2006Toxins that bind to albumin in the bloodstream and are associated with progressing liver failure have proven refractory to removal by conventional hemodialysis. Such... (Review)
Review
Toxins that bind to albumin in the bloodstream and are associated with progressing liver failure have proven refractory to removal by conventional hemodialysis. Such toxins can, however, be removed by adding a binder to the dialysate that serves to capture the toxin as it is dialyzed across the membrane. Several approaches based upon this concept are in various stages of clinical evaluation. The thermodynamic basis common to these approaches has been used to develop an engineering description of 'bound solute dialysis' which has further been used to define the clinical expectations and limitations of the approach. Three dimensionless, independently controllable, operating parameters emerged from this analysis (i): kappa, the dialyzer mass transfer/blood flow rate ratio (clinical range: 0.5-2.5); (ii) alpha, the dialysate/blood flow rate ratio (clinical range: 0.1-2.0); and (iii) beta, the dialysate/blood binder concentration ratio (clinical range: 0.02-5.0). In the absence of binder in the dialysate, bound toxin removal is sensitive to kappa and alpha, with greater removal associated with greater kappa and/or alpha. Bound toxin removal, however, is dependent primarily upon kappa and independent of alpha and beta once a small amount of binder, beta > 0.02, is added to the dialysate. The improvement in bound toxin removal over conventional hemodialysis is dependent upon how tightly the toxin binds albumin ranging from a 6-fold increase for a relatively tightly bound solute such as unconjugated bilirubin, to 1.5-fold increase for a less tightly bound drug such as warfarin at 24 h perfusion time. Clinically, bound solute dialysis can be practiced in single-pass mode with as little as 1-2 g albumin/L dialysate. Because of the constraints imposed by the thermodynamic nature of the process, intervention should be made as early in the disease progression as feasible.
Topics: Albumins; Blood Flow Velocity; Charcoal; Dialysis; Dialysis Solutions; Humans; Liver Failure; Liver, Artificial; Membranes, Artificial
PubMed: 16684212
DOI: 10.1111/j.1744-9987.2006.00352.x -
Advances in Chronic Kidney Disease Jul 2007Attainment of dry weight remains a major clinical problem and challenge in current-day dialysis therapies. The vicious cycle of fluid overload and inadequate... (Review)
Review
Attainment of dry weight remains a major clinical problem and challenge in current-day dialysis therapies. The vicious cycle of fluid overload and inadequate intradialytic fluid removal with hypotensive episodes, and subsequent poor clinical outcomes, is reinforced by excessive salt accumulation orally as well as during dialysis. Negligence in recognizing the importance of fluid status in dialysis prescriptions with shortened times has contributed to the prevalence of overhydration. The treatment of this problem is exacerbated by the lack of adequate methods to diagnose and manage it. The recent findings of improved fluid status and prognosis with salt restriction, individualized dialysate sodium concentrations, and prolonged hemodialysis times when necessary with well-tolerated fluid removal rates show the path to prolonging survival of dialysis populations. The ongoing development of techniques permitting accurate assessment of hydration status, including those based on bioimpedance analysis, will provide an efficient tool in these efforts.
Topics: Body Weight; Dialysis Solutions; Female; Humans; Kidney Failure, Chronic; Male; Quality of Life; Renal Dialysis; Risk Factors; Sodium Chloride; Survival Analysis; Treatment Outcome; Urea; Water-Electrolyte Balance; Water-Electrolyte Imbalance; Weight Gain
PubMed: 17603970
DOI: 10.1053/j.ackd.2007.03.003 -
Advances in Renal Replacement Therapy Apr 1999On-line hemodiafiltration (HDF) provides the largest amount of blood purification over a wide molecular weight spectrum achievable with present renal replacement... (Review)
Review
On-line hemodiafiltration (HDF) provides the largest amount of blood purification over a wide molecular weight spectrum achievable with present renal replacement therapies. When used with state of the art dialysis membranes and treatment systems, the biocompatibility of on-line HDF is as high as can presently be defined. From an economic perspective, the added cost of the ultrafilters used to prepare the substitution solution is balanced by the therapeutic benefits of HDF. For optimal HDF, the ultrafiltration rate must be maximized with respect to the blood flow rate. In on-line HDF systems, the excess volume ultrafiltered, approximately 20 to 30 liters per treatment, is automatically replaced, preferably in postdilution mode, by a substitution solution that is continuously generated by stepwise ultrafiltration of dialysate. When properly prepared, this fluid fulfills the quality demands of commercially available infusion solutions; that is, it can be referred to as sterile and pyrogen-free. The most important factors in preparing substitution solution are the quality of the water, of the concentrates, of the ultrafilters, and the microbiological status of the entire flow path. The clinical safety of substitution solution prepared on-line has been documented by long-term users of on-line systems. Results from clinical studies with on-line HDF confirm the overall increased clearance of solutes in relation to high-flux dialysis using the same membrane.
Topics: Cost-Benefit Analysis; Dialysis Solutions; Hemodiafiltration; Humans; Membranes, Artificial; Online Systems; Renal Insufficiency
PubMed: 10230890
DOI: 10.1016/s1073-4449(99)70038-5 -
Nephrologie & Therapeutique Mar 2019Setting dialysate sodium allows to adequately adjust sodium balance and plasma sodium at the end of dialysis session. In accordance with the set-point theory based on... (Review)
Review
Setting dialysate sodium allows to adequately adjust sodium balance and plasma sodium at the end of dialysis session. In accordance with the set-point theory based on the concept of restoring cellular hydration, an adequate target for plasma sodium at the end of the session could be the value of predialysis plasma sodium concentration (isonatric hemodialysis). Some recently available dialysis monitors provide an on-line value of plasma-water conductivity usually converted in on-line natremia. There are different modalities of isonatric hemodialysis depending on whether the online value of natremia is used or not. By reviewing the few studies concerning the isonatric hemodialysis, it seems logical to set a target of postdialysis on-line natremia (or plasma-water conductivity) slightly lower than its predialysis value. However this strategy requires specifically designed software not yet available in clinical routine.
Topics: Dialysis Solutions; Electric Conductivity; Humans; Hypertonic Solutions; Renal Dialysis; Sodium
PubMed: 29887269
DOI: 10.1016/j.nephro.2018.03.005 -
Seminars in Dialysis 2006Many fundamental aspects of the management of renal replacement therapy (RRT) in acute renal failure (ARF) remain unresolved. While data from multiple studies support... (Review)
Review
Many fundamental aspects of the management of renal replacement therapy (RRT) in acute renal failure (ARF) remain unresolved. While data from multiple studies support the initiation of RRT, in the absence of other indications, when the BUN has reached a level of approximately 90-100 mg/dl, there are conflicting data regarding the benefit of earlier initiation of renal support. The relative efficacy of the various RRT modalities is uncertain. Despite growing utilization, a survival benefit or greater recovery of renal function has not been demonstrated for continuous renal replacement therapy (CRRT) as compared to conventional intermittent hemodialysis (IHD). Optimal dosing strategies are also poorly defined. While there is increasing evidence that more intensive renal support is associated with better outcomes in ARF, an optimal Kt/Vurea and treatment frequency for IHD remain to be established. Similarly, although data suggest that continuous venovenous hemofiltration (CVVH) should be dosed at no less than 35 ml/kg/hr (postdilution), confirmation of this dosing strategy and validation for other modalities of CRRT are required.
Topics: Acute Kidney Injury; Dialysis Solutions; Humans; Renal Dialysis
PubMed: 16551296
DOI: 10.1111/j.1525-139X.2006.00144.x -
Pediatric Nephrology (Berlin, Germany) Dec 2017Products of metabolism accumulate in kidney failure and potentially have toxic effects. Traditionally these uraemic toxins are classified as small, middle-sized and... (Review)
Review
Products of metabolism accumulate in kidney failure and potentially have toxic effects. Traditionally these uraemic toxins are classified as small, middle-sized and protein-bound toxins, and clearance during dialysis is affected by diffusion, convection and adsorption. As current dialysis practice effectively clears small solutes, increasing evidence supports a toxic effect for middle-sized and protein-bound toxins. Therefore, newer approaches to standard dialysis practice are required to look beyond urea clearance. Current dialysers have been developed to effectively clear small solutes and secondly to increase middle-sized toxin clearances. However, there is no ideal dialyser which can effectively clear all uraemic toxins. Advances in nanotechnology have led to improvements in manufacturing, with the production of smoother membrane surfaces and uniformity of pore size. The introduction of haemodiafiltration has led to changes in dialyser design to improve convective clearances. Both diffusional and convectional clearances can be increased by changing dialyser designs to alter blood and dialysate flows, and novel dialyser designs using microfluidics offer more efficient solute clearances. Adjusting surface hydrophilicity and charge alter adsorptive properties, and greater clearance of protein-bound toxins can be achieved by adding carbon or other absorptive monoliths into the circuit or by developing composite dialyser membranes. Other strategies to increase protein-bound toxins clearances have centred on disrupting binding and so displacing toxins from proteins. Just as the hollow fibre design replaced the flat plate dialyser, we are now entering a new era of dialyser designs aimed to increase the spectrum of uraemic toxins which can be cleared by dialysis.
Topics: Dialysis Solutions; Equipment Design; Humans; Kidneys, Artificial; Renal Dialysis; Renal Insufficiency
PubMed: 28401301
DOI: 10.1007/s00467-017-3647-y -
Hemodialysis International.... Apr 2008Accumulation of knowledge requisite for development of hemodialysis started in antiquity and continued through Middle Ages until the 20th century. Firstly, it was... (Review)
Review
Accumulation of knowledge requisite for development of hemodialysis started in antiquity and continued through Middle Ages until the 20th century. Firstly, it was determined that the kidneys produce urine containing toxic substances that accumulate in the body if the kidneys fail to function properly; secondly, it was necessary to discover the process of diffusion and dialysis; thirdly, it was necessary to develop a safe method to prevent clotting in the extracorporeal circulation; and fourthly, it was necessary to develop biocompatible dialyzing membranes. Most of the essential knowledge was acquired by the end of the 19th century. Hemodialysis as a practical means of replacing kidney function started and developed in the 20th century. The original hemodialyzers, using celloidin as a dialyzing membrane and hirudin as an anticoagulant, were used in animal experiments at the beginning of the 20th century, and then there were a few attempts in humans in the 1920s. Rapid progress started with the application of cellophane membranes and heparin as an anticoagulant in the late 1930s and 1940s. The explosion of new dialyzer designs continued in the 1950s and 1960s and ended with the development of capillary dialyzers. Cellophane was replaced by other dialyzing membranes in the 1960s, 1970s, and 1980s. Dialysis solution was originally prepared in the tank from water, electrolytes, and glucose. This solution was recirculated through the dialyzer and back to the tank. In the 1960s, a method of single-pass dialysis solution preparation and delivery system was designed. A large quantity of dialysis solution was used for a single dialysis. Sorbent systems, using a small volume of regenerated dialysis solution, were developed in the mid 1960s, and continue to be used for home hemodialysis and acute renal failure. At the end of the 20th century, a new closed system, which prepared and delivered ultrapure dialysis solution preparation, was developed. This system also had automatic reuse of lines and dialyzers and prepared the machine for the next dialysis. This was specifically designed for quotidian home hemodialysis. Another system for frequent home hemodialysis or acute renal failure was developed at the turn of the 21st century. This system used premanufactured dialysis solution, delivered to the home or dialysis unit, as is done for peritoneal dialysis.
Topics: Equipment Design; Hemodialysis Solutions; History, 19th Century; History, 20th Century; History, 21st Century; History, Ancient; History, Medieval; Humans; Kidneys, Artificial; Renal Dialysis; Renal Insufficiency
PubMed: 18394051
DOI: 10.1111/j.1542-4758.2008.00253.x -
Contributions To Nephrology 2006The peritoneal dialysis system has three major components: the peritoneal microcirculation, the peritoneal membrane, and the dialysate compartment. All these three that... (Review)
Review
The peritoneal dialysis system has three major components: the peritoneal microcirculation, the peritoneal membrane, and the dialysate compartment. All these three that includes the composition of the solution and the modalities of delivery. All these three components may have an important impact on the final performance of the technique. As in the hemodialysis system, factors affecting diffusion of solutes as well as factors affecting convective transport may contribute to the final clearance of a given solute. Ultrafiltration responds to the same pressures applied to the extracorporeal dialysis system, but osmotic gradients represent by far the most important active component.
Topics: Biological Transport; Dialysis Solutions; Diffusion; Humans; Membranes, Artificial; Peritoneal Dialysis; Renal Dialysis
PubMed: 16720985
DOI: 10.1159/000093441 -
Hemodialysis International.... Oct 2016Potassium shifts in thrice weekly HD patients are likely a reversible cause of arrhythmia and sudden cardiac death. In general, a dialysate potassium <2.0 mmol/L should...
Potassium shifts in thrice weekly HD patients are likely a reversible cause of arrhythmia and sudden cardiac death. In general, a dialysate potassium <2.0 mmol/L should be avoided, and many patients with dialysate potassium of 2 mmol/L could safely be adjusted upwards. The ideal predialysis serum potassium should be around 5.0 mmol/L. Trends in serum potassium and not single values, should inform chronic changes of dialysate potassium prescription. Atypical values should be dealt with as a one off, but should not lead to chronic bath changes. Referral to a renal dietician for counseling to limit dietary potassium intake is vital to prevent recurrence of these atypical episodes. Finally, facilities should develop and implement a formal and reliable way to alert the physician about possible potassium bath mismatching. This facility level approach works best if a policy is developed and endorsed by all involved stakeholders.
Topics: Aged, 80 and over; Dialysis Solutions; Humans; Kidney Failure, Chronic; Male; Potassium; Renal Dialysis
PubMed: 27149430
DOI: 10.1111/hdi.12422 -
Critical Care Medicine Jul 2020We designed a novel respiratory dialysis system to remove CO2 from blood in the form of bicarbonate. We aimed to determine if our respiratory dialysis system removes CO2...
OBJECTIVES
We designed a novel respiratory dialysis system to remove CO2 from blood in the form of bicarbonate. We aimed to determine if our respiratory dialysis system removes CO2 at rates comparable to low-flow extracorporeal CO2 removal devices (blood flow < 500 mL/min) in a large animal model.
DESIGN
Experimental study.
SETTING
Animal research laboratory.
SUBJECTS
Female Yorkshire pigs.
INTERVENTIONS
Five bicarbonate dialysis experiments were performed. Hypercapnia (PCO2 90-100 mm Hg) was established in mechanically ventilated swine by adjusting the tidal volume. Dialysis was then performed with a novel low bicarbonate dialysate.
MEASUREMENTS AND MAIN RESULTS
We measured electrolytes, blood gases, and plasma-free hemoglobin in arterial blood, as well as blood entering and exiting the dialyzer. We used a physical-chemical acid-base model to understand the factors influencing blood pH after bicarbonate removal. During dialysis, we removed 101 (±13) mL/min of CO2 (59 mL/min when normalized to venous PCO2 of 45 mm Hg), corresponding to a 29% reduction in PaCO2 (104.0 ± 8.1 vs 74.2 ± 8.4 mm Hg; p < 0.001). Minute ventilation and body temperature were unchanged during dialysis (1.2 ± 0.4 vs 1.1 ± 0.4 L/min; p = 1.0 and 35.3°C ± 0.9 vs 35.2°C ± 0.6; p = 1.0). Arterial pH increased after bicarbonate removal (7.13 ± 0.04 vs 7.21 ± 0.05; p < 0.001) despite no attempt to realkalinize the blood. Our modeling showed that dialysate electrolyte composition, plasma albumin, and plasma total CO2 accurately predict the measured pH of blood exiting the dialyser. However, the final effluent dose exceeded conventional doses, depleting plasma glucose and electrolytes, such as potassium and phosphate.
CONCLUSIONS
Bicarbonate dialysis results in CO2 removal at rates comparable with existing low-flow extracorporeal CO2 removal in a large animal model, but the final dialysis dose delivered needs to be reduced before the technique can be used for prolonged periods.
Topics: Animals; Bicarbonates; Blood Proteins; Carbon Dioxide; Dialysis; Dialysis Solutions; Electrolytes; Female; Hemoglobins; Hypercapnia; Respiration, Artificial; Swine
PubMed: 32304418
DOI: 10.1097/CCM.0000000000004351