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Dialysis fluid contamination of pathways and life of microbes.

The fluid systems of a dialysis clinic are reviewed from a microbiological standpoint. Water, concentrate and dialysis fluid are the main fluids in the clinic. The quality of these fluids cannot be dealt with, without at the same time reviewing the systems delivering these fluids. The handling of fluids must be seen in a system perspective where every part is important. In the pretreatment of water before reverse osmosis, the incoming water determines the quality. After reverse osmosis,the maintenance in form of disinfection activities is decisive for the microbiological quality in the water system. The dialysis fluid quality is dependent on the water quality as it is produced at the end of the water system. It must be noted that it is not only the number of microorganisms that is of importance but also what the microorganisms do in the fluid systems. Microbiological analysis is not normally able to tell the complete microbiological quality of the fluid systems, as the inner surfaces where the microbial growth takes place are not sent to any laboratory. Consequently, what is seen in samples is only what can come off the surface. The only action that can prevent growth of microorganisms is disinfection but disinfection only is not the solution, it must also be performed regularly. Additionally, all areas of the fluid system must be disinfected. The principle of Quality Assurance including equipment, education and maintenance must be applied in order to ensure microbiological quality.

Disinfection↗

[Progresses in the concentration of foodstuffs (author's transl)].

The article reports a description and a comparison of three concentration techniques: evaporation, freeze-concentration and reverse osmosis. The discussion is particularly concerned with the problems of aroma losses and retention and, for evaporation, the problems of heat damage and fouling. The increase in viscosity with concentration and the markedly non-newtonian behaviour of most food products are such that only evaporation allows to achieve high concentrations. The major progresses in evaporation plants and techniques are discussed in terms of heat transfer efficiency and residence time. Freeze-concentration and reverse osmosis are suitable for pre-concentration up to 30-35 10Brix of heat sensitive and aromarich products

Food Preservation↗

[Water treatment systems of hemodialysis centers in Lithuania and trace metals in purified water in 2002].

The objective of this survey was to obtain information on hemodialysis chemical water quality and on water treatment systems of hemodialysis centers in Lithuania. Five trace metals (Al, Pb, Cd, Zn, Cu) were examined in the purified water (sample from a point after the water treatment system) of 28 hemodialysis centers. Atomic absorption spectrophotometry was applied to measure water trace metals levels. All hemodialysis centers in Lithuania used treated water. Softeners were used by 100%, reverse osmosis by 86.2% of the centers. Concomitant use of sand filter, softeners, activated carbon, reverse osmosis was found in 72.4% of the centers. The age of the water treatment system varied from 1 to 117 months (mean=39.7+/-30.4). Concentrations of Al, Pb, Cd, Zn, Cu in the purified water of 28 hemodialysis centers did not exceed standards of the European Pharmacopoeia. There was significant decrease in the mean levels of investigated trace elements in the treated water in Lithuania in 2002 compared with examined in 1998.

Aluminum↗

[Transport of ions in mitochondria in connection with osmotic concentration of media].

Studies on mitochondria has revealed apparent violation of laws of osmosis, apparently, related to ion transport. In this context, we studied changes in the content of potassium, sodium, magnesium, and calcium in mitochondria from wheat (Triticum aestivum L.) roots incubated in the buffer without the substrate with 0.3 or 0.5 M sucrose as well as potassium, and phosphate. The most pronounced changes were observed for potassium. Potassium arrival to mitochondria was more active at 0.5 than 0.3 M sucrose. The direction of the cation transport depended on its content in the initial buffer. At the certain threshold level, the inflow was replaced with the outflow; this threshold was lower at 0.3 than 0.5 M sucrose. Magnesium was also released from mitochondria; its stable outflow was primarily observed at its lower initial content in the suspension at 0.3 rather than 0.5 M sucrose. The obtained data demonstrated that the apparent violation of laws of osmosis was false and resulted from ion transport. Passive ion transport as a possible mechanism of adaptation to osmotic properties of the external medium is discussed.

Cations↗

Re-use of biologically treated wastewater of a brewery.

Despite excessive rainfalls, Flanders is dealing with a water deficiency. A rational use of water is a necessity. Apart from the prevention principle, the re-use of biologically treated wastewater (bio-effluent) is increasingly considered. From earlier research it is known that reverse osmosis (RO) is necessary for the elimination of salts and low molecular compounds from the bio-effluent. A thorough pretreatment is necessary to remove drastically the suspended solids, which are harmful to the reverse osmosis modules. This case study describes the experiments performed by SEGHERSbetter technology for Water N.V. on the treatment of wastewater effluent from a brewery. A comparative study between sand filtration (SF), in-line coagulation with sand filtration and ultrafiltration (UF) as a pretreatment was made. UF proved to be the best pretreatment for RO for the treatment of brewery bio-effluent. Finally, an economic evaluation of the membrane system (UF followed by RO) was made. The calculated total cost for the system is 0.26 Euros per m3 produced water. Investment costs and operation cost are also discussed.

Beer↗

[Guidelines on water and solutions for dialysis. Italian Society of Nephrology].

The National Society of Nephrology has promoted the development of specific Italian Guidelines for dialysis fluids. Two previous national inquiries showed a wide variety in the type and frequency of both microbiological and chemical controls concerning dialysis water, reinforcing the need for specific standards and recommendations. An optimal water treatment system should include tap water pre-treatment and a double reverse osmosis process. Every component of the system, including the delivery of the treated water to the dialysis machines, should prevent microbiological contamination of the fluid. Regular chemical and microbiological tests and regular disinfection of the system are necessary. 1. Chemical quality (Table: see text). Treated tap water used to prepare dialysis fluid should be within European Pharmacopoeia limits at the water treatment system inlet and at the reverse osmosis outlet. In addition dialysate, concentrate and infusion fluids must comply with specific Pharmacopoeia limits. The physician in charge of the dialysis unit is advised to institute a multidisciplinary team to evaluate the requirement for added chemical controls in the presence of local hazards. 2. Microbiological quality (Table: see text). High microbiological purity of dialysis fluid--regularly verified--is a fundamental prerequisite for dialysis quality and every dialysis unit should aim as a matter of course to obtain "ultra-pure" dialysate (microbial count <0.1 UFC/mL, endotoxins <0.03 U/mL). On-line dialysate ultrafiltration and regular disinfection of dialysis machines greatly enhance microbiological purity. On-line dialysate reinfusion requires specific devices used according to corresponding instructions and to more frequent microbiological tests. Dialysis fluids for home dialysis should comply with the same chemical and bacteriological quality. The appendix reports the water treatment system's technical characteristics, sampling and analytical methods, monitoring time-tables, as well as the origin and effects of the main toxic substances. Suggestions and questions concerning these guidelines are welcome to nefrologia@sin-italy.org.

Colony Count, Microbial↗

[Maintenance and monitoring of water treatment system].

Water treatment systems must be submitted to maintenance, disinfections and monitoring periodically. The aim of this review is to analyze how these processes must complement each other in order to preserve the efficiency of the system and optimize the dialysis fluid quality. The correct working of the preparatory process (pre-treatment) and the final phase of depuration (reverse osmosis) of the system need a periodic preventive maintenance and the regular substitution of worn or exhausted components (i.e. the salt of softeners' brine tank, cartridge filters, activated carbon of carbon tanks) by a competent and trained staff. The membranes of reverse osmosis and the water distribution system, including dialysis machine connections, should be submitted to dis-infections at least monthly. For this purpose it is possible to use chemical and physical agents according to manufacturer' recommendations. Each dialysis unit should predispose a monitoring program designed to check the effectiveness of technical working, maintenance and disinfections and the achievement of chemical and microbiological standards taken as a reference. Generally, the correct composition of purified water is monitored by continuous measuring of conductivity, controlling bacteriological cultures and endotoxin levels (monthly) and checking water contaminants (every 6-12 months). During pre-treatment, water hardness (after softeners) and total chlorine (after chlorine tank) should be checked periodically. Recently the Italian Society of Nephrology has developed clinical guidelines for water and dialysis solutions aimed at suggesting rational procedures for production and monitoring of dialysis fluids. It is hopeful that the application of these guidelines will lead to a positive cultural change and to an improvement in dialysis fluid quality.

Disinfection↗

Water treatment in domiciliary hemodialysis equipment: ultraviolet irradiation and Sartobind membrane.

Water is a fundamental element in any hemodialysis device. It must be safe, free not only of micro-organisms but also of any organic or inorganic chemical contaminant. Up to now ion exchanger, reverse osmosis, activate carbon and chlorine are generally used for this purpose. The results are not satisfactory. Microbial contaminants survive and at some points multiply. Pyrogens and endotoxins are not completely eliminated. Chlorine itself adds more risk factors because of the compounds deriving from its interaction with organic molecules. A system to obtain safe water in hemodialysis equipment is described. It is based on the use of ultraviolet irradiation to eliminate any microbial contaminant and on Sartobind membranes to eliminate pyrogens, endotoxins, proteins and other unwanted molecules. Mobile domiciliary hemodialysis equipment was used. Ultraviolet lamps (30 mW/cm2) were applied at two points: after the ion exchange and after the reverse osmosis. Three Q100 Sartobind membranes were positioned immediately before the monitor. The values of cfu/mL counted in the water after the ion exchange ranged from 450 to 1,990, whereas before the monitor they dropped from 0.01 to 0.09 cfu/mL. The LAL test, positive before the Sartobind membrane, was negative thereafter. The system proposed has shown to be effective in guaranteeing safe water free of micro-organisms and endotoxins.

Hemodialysis, Home↗

[Detection of sorbitol content in crystalline lens of normal rats and rats with diabetic cataract by 1H-NMR].

The pulse Fourier NMR was employed to measure the artificial diabetic cataract lens at various stages of its formation, and the lenses of the normal rats. Data obtained by using this method show that all the peaks that of water concentrate in the range of delta less than 4 ppm. The peak value at delta = 3.20 ppm is on a marked increase during the formation of cataract which is caused by the phosphate metabolites, such as GPC, ATP, ... etc, in cataract lens. With the development of the disease, the peak width at delta = 3.73 ppm becomes greater and greater, which shows that the activity of sorbitol dehydrogenase has decreased. This leads to a high concentration of the sorbitol in the cataract lens. Consequently, the osmosis pressure in the cataract lens is increased, and excessive water might dip into the crystalline lens to keep the balance of the osmosis pressure. And this might result in the hydration of the fiber cell of the crystalline lens, which might cause a swelling or blisters. These results are in favour of the prolongation of the relaxation time of cataractous lens reported in our other papers, and also support those gained by biochemical studies issued in the medical literature.

Animals↗

[Ability to remove pesticides in the production of dialysis water (1)].

In many cases it can be demonstrated that the amount of plant protective and plant treatment substances (pesticides) in drinking water exceeds the permitted levels of the drinking water ordinance which will come into effect on October 1st, 1989. Since some of these components are of toxicological relevance, an investigation was done on how far pesticides are removed during conventional purification of dialysis water, and especially during reverse osmosis. The retention rates of a reverse osmosis plant for 14 different pesticides applied in different concentrations and compositions were determined. Almost all of the substances examined were retained with an effectiveness of 92-98%. The elimination efficiency did not depend on the initial concentration of the pesticides. After an initial phase of 50 h duration, the concentration in the treated water reached a constant value which no longer changed even after more than 700 h. In part 1 of this contribution at first the fundamentals of dyalisis water purification are reviewed and a selection of the pesticides to be investigated is carried out. In addition experimental set up and procedure are described.

Filtration↗

[Bacteriologic studies of bicarbonate dialysate and suitable initial solutions].

Dialysates for the haemodialysis are produced unsterile and usually contain bacteria. Own investigations of bicarbonate dialysate and adequate initial solutions comprised sterility tests, determinations of the germ count and germ tolerance experiments. Only the "acid concentrate" was sterile. In the other solutions Corynebacteria, Acinetobacter and Pseudomonas bacteria dominated as typical water germs. In the fresh reverse osmosis water and the bicarbonate dialysate as well as in the recently produced 35-mmolar and 1-molar NaHCO3-solution the germ count was in each case about 10(5)/l and did not change itself essentially at room temperature within 6 hours. The "acid concentrate" and at a lower level also the 1-molar NaHCO3-concentrate have an antibacterial effect. The reverse osmosis water is the main contamination source for the bicarbonate dialysate, the application of which within 6 hours seems worth being used on account of the low germ count.

Bacteriological Techniques↗

Vascular potential and thrombosis.

The electrochemical phenomena related to the negative charge of blood cells have provided a means of defining the importance of these parameters in vascular thrombosis. In parallel with these works, measurements of transmembrane potential have revealed that the vessel wall also carries negative charges and thus takes part in the repulsion of blood cells and prevents them from being adhesive on the intima. These charges come from various origins (ion or protein adsorption, active transfer through the vascular wall, ionized groups...). Vascular potential can be approached by means of various techniques: transmembrane potential (electro-osmosis), circulation potential (in vitro and in vivo). On the basis of published results and his own personal research, the author compares the different values that have been obtained. Consequently, it has been observed that the transmembrane charge measurements that are accessible using electro-osmosis techniques and streaming potential do reflect some discordances according to the methods used. The importance of these parameters and the part they play in thrombosis phenomena is discussed.

Adsorption↗

Vascular potential and thrombosis.

The electrochemical phenomena related to the negative charge of blood cells have provided a means of defining the importance of these parameters in vascular thrombosis. In parallel with these works, measurements of transmembrane potential have revealed that the vessel wall also carries negative charges and thus takes part in the repulsion of blood cells and prevents them from being adhesive on the intima. These charges come from various origins (ion or protein adsorption, active transfer through the vascular wall, ionized groups ...). Vascular potential can be approached by means of various techniques: transmembrane potential (electro-osmosis), circulation potential (in vitro and in vivo). On the basis of published results and his own personal research, the author compares the different values that have been obtained. Consequently, it has been observed that the transmembrane charge measurements that are accessible using electro-osmosis techniques and streaming potential do reflect some discordances according to the methods used. The importance of these parameters and the part they play in thrombosis phenomena is discussed.

Animals↗

Contamination of dialysis water and dialysate. A survey of 30 centers.

The concentration of bacteria and endotoxin in dialysis water and dialysate of 30 dialysis centers in western Germany was examined. Water samples were obtained after treatment by reverse osmosis or other processing methods. Collection of dialysis samples for bacterial, fungal, and endotoxin analysis was conducted before and 2 hours after start of hemodialysis. In 17.8% of all water samples analyzed, the AAMI standard was exceeded and bacterial and fungal counts greater than 200 colony forming units/ml were found. In 11.7% of all dialysate samples, higher contamination than the recommendations for dialysate of 2000 colony forming units/ml were found. The concentration of endotoxin in water and dialysate varied between 0 and 95 endotoxin units in the water samples and 0 and 487 endotoxin units/ml in the dialysate samples. In 12.2% of all water sampled, and 27.5% of all dialysate samples, values of 5 endotoxin units/ml were found. No correlation was found between the level of contamination of either water or dialysate in a specific center and the following factors: water processing method (reverse osmosis or others), type of dialysate (acetate of bicarbonate), type of dialysate machine, or method of machine disinfection. In view of these results it is suggested that endotoxin testing, especially in the dialysate, be a part of regular quality control in dialysis.

Bacteria↗

Theoretical analysis of osmotic agents in peritoneal dialysis. What size is an ideal osmotic agent?

In this article the difference between osmotic fluid flow (ultrafiltration) as driven by osmotic pressure and diffusion through thin leaky membranes is discussed. It is pointed out that water transport induced by osmosis is fundamentally different from the process of water diffusion. Applying modern hydrodynamic pore theory, the molar solute concentration and the solute concentration in grams per 100 mL, exerting the same initial transmembrane osmotic pressure as a 1% glucose solution, was investigated as a function of solute molecular weight (MW). It was then assumed, base on experimental data, that the major pathway responsible for the peritoneal osmotic barrier characteristics is represented by pores of radius approximately 47 A. With increasing solute radius, the osmotic reflection coefficient (sigma) and, hence, the osmotic efficiency per mole of solute will increase. However, simultaneously, the molar concentration per unit solute weight will decrease. The balance point between these two events apparently occurs at a solute MW of approximately 1 kDa. An additional advantage of using solutes of high MW as osmotic agents during peritoneal dialysis (PD), rather than increased osmotic efficiency per se, lies in the fact that large solutes, due to their low peritoneal diffusion capacity, will maintain a sustained rate of ultrafiltration (osmosis) over a prolonged period. To illustrate this, we have performed computer simulations of peritoneal fluid transport according to the three-pore model of peritoneal permselectivity. According to these simulations, 4% of an 800 Da polymer solution (+50 mmol/L above isotonicity) will produce the same cumulative amount of intraperitoneal fluid volume ultrafiltered (UF) during 360-400 minutes as 4% of a 2 kDa polymer solution (+20 mmol/L) or 6.5% of a 10 kDa polymer solution (+6.5 mmol/L) having the same electrolyte concentration as dialysis solutions conventionally used for PD. Similar cumulative UF volumes (during 400 minutes) can be obtained by a 2.5% glycerol (+272 mmol/L) or a 3.2% glucose-containing dialysis solution (+177 mmol/L) with conventional electrolyte composition.

Dialysis Solutions↗

THE ELECTROOSMOTIC EFFECTS ARISING FROM THE INTERACTION OF THE SELECTIVELY ANION AND SELECTIVELY CATION PERMEABLE PARTS OF MOSAIC MEMBRANES.

It has been previously shown, theoretically and in model system experiments, that mosaic membranes composed of anion-selective (electropositive) and cation-selective (electronegative) parts interposed between electrolytic solutions of different concentrations give rise to local electrical circuits. In this work with model systems it is shown that these currents produce electroosmosis. In systems with permselective electronegative membranes and KCl solutions, the electroosmotic water transport was 16 moles/faraday. With the permselective electronegative membrane replaced by more porous electronegative membranes, the electroosmotic effects were about twice as high. With Li salts, the water transport was considerably larger. A system with a permselective electropositive membrane of 50 cm(2) effective area and an electronegative membrane of 120 cm(2) gave internally generated currents up to 20 ma. In extrapolating from the results with macromodels to effects with true mosaics, i.e. microsystems, it is stressed that current depends on the linear distance over which membranes interact. In true mosaic membranes, the current pathways will be of the same order as the dimensions of individual membrane microelements; the sum of all local microcurrents will be correspondingly larger than the current in the macromodel, and the electroosmotic effects will be proportionately greater. Electroosmotic effects with true charge-mosaic membranes may be of the same order or larger than the liquid transport by normal and anomalous osmosis which might occur across the individual parts of the charge-mosaic.

Biophysical Phenomena↗

Water exchange of collagenous tissues and of gelatin.

Water exchange of parenchymatous tissue, namely liver, kidney, or pancreas, occurs by osmosis, and the movement of water, as is well known, occurs in direct relation to the concentration of the surrounding solution. But the present work shows that the hydration of collagenous tissues, like that of gelatin, occurs in strong as well as in weak solutions of sodium chloride. The water intake of collagenous tissue in solutions of sodium chloride or of sucrose increases with increased density of the tissue and the sequence of changes is like that observed with gels of increasing gelatin content under the same conditions. Dense collagenous tissue, apparently impervious to the movement of water, exhibits a conspicuous ability to attract and hold it.

Collagen↗

THE MECHANISM OF ISOTONIC WATER TRANSPORT.

The mechanism by which active solute transport causes water transport in isotonic proportions across epithelial membranes has been investigated. The principle of the experiments was to measure the osmolarity of the transported fluid when the osmolarity of the bathing solution was varied over an eightfold range by varying the NaCl concentration or by adding impermeant non-electrolytes. An in vitro preparation of rabbit gall bladder was suspended in moist oxygen without an outer bathing solution, and the pure transported fluid was collected as it dripped off the serosal surface. Under all conditions the transported fluid was found to approximate an NaCl solution isotonic to whatever bathing solution used. This finding means that the mechanism of isotonic water transport in the gall bladder is neither the double membrane effect nor co-diffusion but rather local osmosis. In other words, active NaCl transport maintains a locally high concentration of solute in some restricted space in the vicinity of the cell membrane, and water follows NaCl in response to this local osmotic gradient. An equation has been derived enabling one to calculate whether the passive water permeability of an organ is high enough to account for complete osmotic equilibration of actively transported solute. By application of this equation, water transport associated with active NaCl transport in the gall bladder cannot go through the channels for water flow under passive conditions, since these channels are grossly too impermeable. Furthermore, solute-linked water transport fails to produce the streaming potentials expected for water flow through these passive channels. Hence solute-linked water transport does not occur in the passive channels but instead involves special structures in the cell membrane, which remain to be identified.

Animals↗