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PubMed1978

Influence of ultrafiltration on plasma renin activity and adrenergic system.

The influence of efficient ultrafiltration without dialysis fluid was compared to the standard dialysis technique in two groups of 4 patients with chronic renal failure on maintenance haemodialysis. Supine plasma renin activity (PRA), plasma concentration of noradrenaline (NA), and adrenaline (A) and the Valsalva manoeuvre were determined before and after the period of ultrafiltration at the beginning and at the end of the experiment. The behaviour of these parameters was related to changes of blood pressure and body weight. The rapid weight loss was well tolerated during ultrafiltration only, with a significant increase of plasma catecholamines concentration; in contrast, patients treated with ultrafiltration and dialysis showed no significant increase of NA and A levels and they frequently became hypotensive. No relationship was observed between changes in PRA and those in body weight and blood pressure. Our data suggest that rapid removal of catecholamines during standard dialysis hinders the compensatory increase of the adrenergic activity and is responsible for hypotension.

Blood Pressure↗

PubMed1988

Pharmacological reduction of lymphatic absorption from the peritoneal cavity increases net ultrafiltration and solute clearances in peritoneal dialysis.

Lymphatic drainage from the peritoneal cavity occurs mainly via the subdiaphragmatic stomata and significantly reduces net ultrafiltration and solute clearances during long-dwell peritoneal dialysis. Intraperitoneal cholinergic drugs constrict these stomata and may reduce peritoneal cavity lymphatic absorption. We evaluated ultrafiltration kinetics, solute transport, and lymphatic drainage during single hypertonic exchanges in rats using 2.5% dextrose dialysis solution with and without added neostigmine. Net ultrafiltration was enhanced in the neostigmine group (p less than 0.01) by a reduction in cumulative lymphatic absorption (p less than 0.01) and without an increase in total transcapillary ultrafiltration during the dwell time. Likewise solute clearances were significantly augmented with neostigmine primarily due to the increase in dialysate drain volume (p less than 0.01) since dialysate/serum solute ratios were unchanged. Pharmacological manipulation of peritoneal lymphatic absorption provides an alternative means of increasing the efficiency of long-dwell peritoneal dialysis without altering peritoneal transport of solutes and water.

Absorption↗

PubMed2005

Fluid and solute transport in CAPD patients before and after permanent loss of ultrafiltration capacity.

BACKGROUND: Two major types of permanent loss of ultrafiltration capacity (UFC) were previously distinguished among patients treated with CAPD: 1) type HDR with high diffusive peritoneal transport rate of small solutes and low osmotic conductance,but with normal fluid absorption rate, and 2) type HAR with high fluid absorption rate, but with normal diffusive peritoneal transport rate of small solutes and normal osmotic conductance. However, the detailed pattern of changes in peritoneal transport parameters in patients developing loss of ultrafiltration capacity is not known. OBJECTIVE: Analysis of solute and fluid transport parameters in the same patient before and after UFC loss. PATIENTS: Seven CAPD patients who had undergone repeated dwell studies,which were carried out before and/or after the onset of UFC loss. METHODS: Dialysis fluids (2 L) with glucose or a mixture of amino acids as osmotic agent at three basic tonicities were applied during 6 hour dwell studies. Fluid and solute transport parameters were previously shown not to be affected by these dialysis solutions (except by hypertonic amino acid-based solution). Intraperitoneal dialysate volume and fluid absorption rate were assessed using radiolabeled human serum albumin (RISA). Osmotic conductance (a(OS))was estimated by a mathematical model as ultrafiltration rate induced by unit osmolality gradient. Diffusive mass transport coefficients, K(BD), for glucose,urea,and creatinine were estimated using the modified Babb-Randerson-Farrell model. RESULTS: Five patients had increased K(BD) for small solutes after the onset of UFC loss,and three of them had decreased a(OS),whereas two patients had normal a(OS). In one of them, a(OS) decreased with time after the onset of UFC loss with concomitant normalization of glucose absorption. In all studies of these five patients the fluid absorption rate was within the normal range. Two other patients had increased fluid absorption rate (about 5 ml/min),and one of them also had increased K(BD) for small solutes,in two consecutive dwell studies in each patient with the second study being carried out at 1 and 7 months respectively after the first one. In all four studies in these two patients, the a(OS) was within the normal range. The sodium dip during dialysis with 3.86% glucose-based solution was lost, not only among most patients with UFC loss related to reduced osmotic conductance, but also in patients with increased K(BD). CONCLUSIONS: The occurrence of two major types of UFC loss was confirmed. However, a case of a mixed type of UFC loss with high fluid absorption rate and high K(BD) for small solutes, but normal osmotic conductance, and with normalization of initially high K(BD) for small solutes, linked with decreasing initially normal osmotic conductance,was also found. As a reduced sodium dip with hypertonic glucose solution is not only seen in patients with reduced osmotic conductance, it cannot reliably be used as a single measure of decreased aquaporin function. Permanent ultrafiltration capacity loss may be a dynamic phenomenon with a variety of alterations in peritoneal transport characteristics.

Adult↗

PubMed2001

Impact of sodium and ultrafiltration profiling on hemodialysis-related symptoms.

Dialysate sodium and ultrafiltration profiling are two methods to reduce symptoms during hemodialysis. The objective of the study was to determine the efficacy of combining these techniques to reduce symptoms in chronic hemodialysis patients. Blood volume changes were measured to determine whether any benefit of profiling could be explained through this mechanism. Patients were randomized to profiled dialysate sodium and ultrafiltration or constant dialysate sodium and ultrafiltration. The study was a two-period, two-treatment, crossover design with repeated measures. The primary outcome was hypotension and/or symptomatic events observed by the dialysis nurse. Secondary outcomes were symptom survey scores, weights, BP, and blood volume changes. Thirty-three patients were randomized. On standard treatment, 30.6% of dialysis sessions were symptomatic compared with 20.4% on profiled treatments. The odds ratio for the development of hypotension or symptomatic event on profiled treatments was 0.61 (95% confidence interval, 0.39 to 0.96) compared with standard treatment. Patients had lower symptom scores by questionnaire in both the intradialytic and the interdialytic periods during profiled treatments. Predialysis weight was greater during profiled treatments by 0.3 kg (P: = 0.008), but there were no differences in postdialysis weight, BP, or thirst. There was no difference in maximum decrease in blood volume during the two treatments (standard, -11.2%; profiled, -10.0%; P: = 0.08), but there was a significant difference in the rate of change in blood volume (standard, -2.96%/h; profiled, -1.96%/h; P: < 0.001). Decrease in blood volume, rate of change in blood volume, and predialysis weights were not associated with hypotension or symptomatic dialysis sessions. In conclusion, dialysate sodium and ultrafiltration profiling significantly reduces hemodialysis-related symptoms. Profiling reduces the slope of the blood volume curve during dialysis, but blood volume changes are not predictive of symptomatic events for an individual patient.

Aged↗

PubMed1979

A simple method for incorporating single pass dialysate delivery and controlled ultrafiltration with the RP-6 high flux dialyzer.

A simple hemodialysis protocol has been developed to permit significant "middle molecule" clearance, yet retain normal low molecular weight clearance. The high flux RP-6 dialyzer has been combined with a single pass dialysate delivery system to provide accurate control of ultrafiltration without resorting to specialized or expensive equipment. By operating the RP-6 in the co-current mode, a simple valve on the dialysate output can be used to regulate ultrafiltration. At QB = 200 ml/min and QD = 500 ml/min, CU = 127 ml/min and CB12 = 56 ml/min at zero ultrafiltration rate; these values increase considerably with ultrafiltration. This protocol offers dialysis centers with standard equipment the opportunity to use high flux membranes in a routine manner.

Animals↗

PubMed1987

Ultrafiltration in diuretic-resistant cardiac failure.

Ultrafiltration was performed in 13 patients with diuretic-resistant cardiac failure. All patients had severely distressing peripheral edema and ultrafiltration was successfully completed in 12 patients, all of whom sustained symptomatic improvement. The volume of fluid removed ranged from 3.7 to 23 L, mean 11.8 L. Weight reduction produced by ultrafiltration continued over the following week, indicating an improved response to diuretic therapy. Ultrafiltration is an effective therapeutic intervention in the management of a small but well-defined group of patients with diuretic-resistant cardiac failure.

Aged↗

PubMed2003

Process for calcium retention during skim milk ultrafiltration.

Lactose is separated from milk or other fluid dairy products for a variety of reasons. Ultrafiltration is a known process of removing lactose from these products. However, during ultrafiltration, valuable minerals, such as calcium in soluble form, are also lost into permeate. In this study, a process was developed in which first the lactose reduction in skim milk was achieved by ultrafiltration (4x volumetric concentration) using a 10-kDa membrane. Then, the calcium present in permeate was precipitated using one of three methods: 1) heat treatment, 2) pH adjustment, or 3) a combination of pH adjustment and heat treatment to permeate, then recovered by refiltering permeate. The process was first developed at laboratory scale, and then its applicability was tested at the pilot scale. Skim milk, retentates, permeates, and the treated permeates were analyzed for total solids, ash, protein, or total nitrogen, calcium, and lactose content. About 76% of the total lactose and about 16% of the calcium present in skim milk permeated through the membrane during ultrafiltration. The three treatments applied produced white precipitates and turned the clear permeates turbid. On refiltering the treated permeates approximately 42, approximately 50, and approximately 70% of the total calcium present could be recovered from 1) heat-treated, 2) pH-adjusted, and 3) pH-adjusted and heat-treated permeates, respectively. There was no marked change in the lactose content due to any of the three treatments and subsequent refiltering of the treated permeates.

Animals↗

PubMed1991

The technique of slow continuous ultrafiltration. Steps to maintain fluid balance without hemodynamic instability.

Slow continuous ultrafiltration (SCUF) is ideally suited for fluid overloaded patients with renal insufficiency, and for patients who need intravenous fluids in amounts that exceed renal excretory capacity. Like other methods of continuous ultrafiltration, including CAVH and CAVHD, SCUF can be performed in the intensive care unit with a minimum of equipment. During SCUF, arterial blood (usually from the femoral artery) is passed through a hollow-fiber hemofilter; an ultrafiltrate of serum collects at a rate that is determined by the patient's blood pressure. Replacement of intravenous fluids is generally not required with SCUF. The amount of ultrafiltrate that is removed can be titrated to achieve the desired fluid balance.

Acute Kidney Injury↗

PubMedDate not supplied

Performance and clinical use of a convertible hemodialysis (HD) - ultrafiltration (UF) system.

A hemodialysis-ultrafiltration system has been developed and evaluated. It may be used either as a conventional hemodialyzer or as a nondialytic ultrafilter. When used as a dialyzer an ultrafiltration controller is required to fix ultrafiltration rate at the desired level. Rates of low molecular solute removal are compatible with those observed in commercially available artificial kidney systems, higher clearances are obtained for middle molecules, and the rate of ultrafiltration can be controlled within narrowly prescribed limits.

Blood Flow Velocity↗

PubMed1999

Screening for xenobiotic electrophilic metabolites using pulsed ultrafiltration-mass spectrometry.

A pulsed ultrafiltration-mass spectrometric screening assay has been developed to generate and identify electrophilic metabolites of xenobiotic compounds formed by hepatic cytochrome P450 enzymes. This assay would be suitable for the early identification of potentially toxic compounds during the initial phase of drug development. Rat liver microsomes were trapped by an ultrafiltration membrane in a stirred flow-through chamber, and substrates for microsomal cytochrome P450 including hydroxychavicol, 3-methylindole, cyproheptadine and 2-tert-butyl-4,6-dimethylphenol were flow-injected individually through the chamber along with the cofactors, NADPH and glutathione. Metabolites and glutathione conjugates were detected on-line using electrospray mass spectrometry. Alternatively, the ultrafiltrate was concentrated on a reversed phase HPLC column and analyzed using electrospray LC-MS or LC-MS-MS to separate and characterize isomeric metabolites and metabolites present at low concentration. Enzymatic activation of each xenobiotic substrate produced highly electrophilic metabolites such as quinones, quinone methides and imine methides that reacted with glutathione on-line to produce glutathione conjugates which were detected by using electrospray mass spectrometry. Although epoxides such as cyproheptadine epoxide were generated, it is likely that these compounds were insufficiently reactive to form glutathione conjugates in the absence of cytosolic glutathione S-transferases. Pulsed ultrafiltration-electrospray mass spectrometry offers an efficient method for in vitro formation and mass spectrometric characterization of activated microsomal drug metabolites and is suitable for use during the drug discovery process for the early identification and screening out of potentially toxic lead compounds.

Animals↗

PubMed1998

Screening for inhibitors of dihydrofolate reductase using pulsed ultrafiltration mass spectrometry.

A method of screening combinatorial libraries for inhibitors of eukaryotic dihydrofolate reductase has been developed using pulsed ultra-filtration electrospray mass spectrometry, which is a continuous-flow affinity separation system for extracting and identifying high affinity ligands in combinatorial libraries. In this application, pulsed ultrafiltration conditions were optimized for the isolation and identification of inhibitors of dihydrofolate reductase from a 22 compound library containing six known inhibitors of the enzyme including trimethoprim, aminopterin, methotrexate, pyrimethamine, folic acid, and folinic acid, and 16 compounds without known affinity. In order to optimize the screening method, sources of non-specific binding were identified and minimized. A significant source of non-specific binding for this set of library compounds was hydrophobic interaction with the surfaces of the ultrafiltration chamber. After affinity separation of bound (high affinity) versus free (low affinity) library compounds during pulsed ultrafiltration, receptor-bound ligands were released and eluted using either organic solvent or acidified mobile phase. Although 80% methanol easily disrupted the receptor-ligand complexes, organic solvent had the undesirable effect of releasing non-specifically bound compounds from the chamber and thereby increasing the background noise. Interference from non-specific binding was minimized by releasing bound ligands using a low pH mobile phase eluent instead of organic solvent. Under the conditions used, pulsed ultrafiltration mass spectrometry selectively identified the two library compounds with the highest affinity for dihydrofolate reductase, methotrexate and aminopterin.

Animals↗

PubMed1999

Failure of icodextrin to provide adequate ultrafiltration in continuous ambulatory peritoneal dialysis patients.

Icodextrin, a starch-derived glucose polymer with an average molecular weight of 20,000 D, has been developed partly as a response to some of the disadvantages of dextrose. It has been suggested that icodextrin solutions are able to provide sustained ultrafiltration (UF) over long dwell times of 8-12 hours in continuous ambulatory peritoneal dialysis (CAPD). In this paper we describe three patients on CAPD: 2 males and 1 female aged 60, 67, and 58 years respectively, duration on CAPD 47, 60, and 15 months respectively. All of these patients, who were categorized as high transporters according to peritoneal equilibration test (PET) results, presented early signs of ultrafiltration loss with no evidence of peritoneal inflammation. Icodextrin solution was used in a single nightly exchange with 10-12 hours' dwell, for a period of 5-30 days. In all of these cases, icodextrin solution failed to provide adequate ultrafiltration and the patients returned to the previously used regime of five daily hypertonic exchanges of 3.86% glucose concentration. Although these negative results were not clearly explained, we report these three cases because they exemplify some limitations of icodextrin solution to provide adequate ultrafiltration, at least in a small number of CAPD patients.

Aged↗

PubMed2001

Efficient and predictable recovery of viruses from water by small scale ultrafiltration systems.

Current methods to concentrate viruses from large volumes of water are prone to inconsistent results and are costly and complex procedurally. Ultrafiltration can utilize size exclusion rather than adsorption and (or) elution to concentrate viruses and, therefore, may offer greater flexibility in developing methods that can provide more consistent recoveries among different viruses and widely varying water conditions. Two small scale ultrafiltration systems (hollow fiber and tangential flow) were tested with a virus suspended in 2 L of reagent grade, tap, ground, or surface water. Three model viruses were used (bacteriophages PP7 and T1 and poliovirus) to compare and characterize the recovery of viruses with the two ultrafiltration systems. Pretreatment of the ultrafilters with blocking agents and the use of elution agents can serve to prevent viral adsorption to the filter surface or to elute bound virus and keep viral agents suspended in the retentate. The use of a blocking and elution step concentrated viruses (>60% recovery) from widely varying water qualities, including surface water, such that a single method can be used to efficiently concentrate viruses from all of the water types tested. Both ultrafiltration systems appear to be able to efficiently recover viruses; however, the hollow fiber systems provided slightly better results in the 2-L volumes tested.

Acrylic Resins↗

PubMed1976

Detrimental effects of ultrafiltration on diffusion in coils.

Previous studies in dialysis coils have suggested decreases in diffusive transport with ultrafiltration. The present studies were designed to test whether increasing blood channel width, alterations in concentration gradients, or molecular sieving at high ultrafiltration rates might explain the phenomenon. Increases in blood channel width and molecular sieving can account only in part for the decreases in diffusion observed. The results suggest that ultrafiltration causes alterations in transmembrane concentration gradients from blood to bath presumably associated with solute accumulation on the bath side of the membrane or may alter bath flow kinetics. Increases in total dialysance with ultrafiltration would be even greater if decreases in diffusive transport could be prevented.

Diffusion↗

PubMed2000

[ATP synthesis by free yeast catalysis coupling hollow fiber ultrafiltration separation].

A novel process for the ATP production employing free yeast catalysis and coupling a hollow fiber module ultrafiltration separation was studied. The experimental results of biocatalyst half-life and operating stability for ultrafiltration showed that the enzymes released from free yeast cell could be cut-off efficiently from the product output stream by hollow fiber membrane. The intercepted percentage of ADH and HK reached more than 95% during the steady running. The efficiency of enzymes utilized was 2.0-2.5 fold as much as that of batch reaction. And the time of yeast cells used repeatedly for ATP synthesis reached 2.5-3.0 batches. Under 0.1 MPa, the ultrafiltrating speed of hollow fiber membrane could keep on a stabilizing value for 11 batches continuously. The continuous operation mode of ATP synthesis simultaneous product ultrafiltration separation could be maintained in higher conversion rate for 5.0 h when the whole system fell in a pseudo-stat where the dilution rate was equal to 0.25 h-1.

Adenosine Triphosphate↗

PubMed1992

[Interrelation of plasma volume, fluid metabolism and neurohormonal activation after ultrafiltration in congestive heart failure].

Ultrafiltration improves the clinical condition of patients with congestive heart failure (CHF) through a reduction of excessive body water. We investigated the relationships among intra and extravascular fluids, hemodynamics and neurohumoral pattern following plasma water subtraction. In 55 patients with CHF (35 in NYHA class IV, Group A, and 20 in NYHA class II-III, Group B), removal of 3242 +/- 201 ml and 1741 +/- 119 ml of plasma water acutely reduced plasma volume (calculated from hematocrit changes) by -20.7% and -12.9% in Group A and in Group B, respectively. Plasma volume returned to baseline values within 48 hours. Body weight and ventricular filling pressures also lowered and remained so for 2 days. After ultrafiltration urinary output increased and norepinephrine, renin activity and aldosterone plasma levels decreased in Group A, while a fall of diuresis and a rapid rise of plasma levels of the 3 hormones were observed in Group B. Two days after ultrafiltration the persistence of reduced body weight with recovery of plasma volume indicates a shift of fluid from the extravascular to the intravascular compartment. The different behaviour of hemodynamics, urinary output and neurohumoral pattern changes observed in the 2 groups after ultrafiltration, suggest that in severe heart failure (Group A) the physiological responses to intravascular volume depletion are unsettled while are preserved in less severe stages of the disease (Group B).

Adult↗

PubMed2006

[Removal of metal ions and dissolved organic compounds in the aqueous solution via micellar enhanced ultrafiltration].

With continuing stringent environmental regulation, the traditional techniques are incapable of reducing the concentration of dissolved organics and heavy metals to the levels required by law or prohibitively expensive. Surfactant-based separation process such as micellar-enhanced ultrafiltration has been extensively proposed. Micellar-enhanced ultrafiltration has been demonstrated to be effective in removal of heavy metals and/or organic contaminants from wastewater stream. The process can be low energy cost and easily included in a whole process. Micellar-enhanced ultrafiltration has been shown to be a promising method for the removal of low-levelsof heavy metal ions and organic compounds from industrial effluents. This paper introduces the working mechanism, main factors of MEUF and the selection of surfactant and membrane. The lasted study progress on the application of micellar-enhanced ultrafiltration is reviewed. The recovery and reuse of surfactant from the retentate and permeate are also discussed.

Metals, Heavy↗

PubMed1991

[Double profile dialysis: ultrafiltration and sodium variable description and clinical validation in the child].

Despite significant technical improvements (bicarbonate dialysate, volumetric ultrafiltration control) high intradialytic ultrafiltration is troublesome in children, specially in the proportion of patients presenting a normal or low blood pressure even with overweight. We used, in this group of children (overhydratated without vascular repercution) a modelling of both sodium and ultrafiltration during dialysis, in order to achieve dry body weight without increasing session time despite hypotension risks. The usefulness and practicability of sodium and ultrafiltration modelling together during dialysis in children is analysed in a short time study (for plasma volume changes calculation) and in a long term follow up study over a year (for clinical tolerance). Today, we reserve this form of dialysis only for a single session needed by overhydratation (more than 5% of dry body weight) in order to achieve dry body weight maintaining dialysis session time constant without increasing side effects (hypotension).

Blood↗