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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↗

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↗

PubMed1977

Experience with a low volume ultrafiltration cell in small children*.

A low volume (16 ml) ultrafiltration cell was used ten times in two small, fluid overloaded children to remove plasma water. The device was simple to use and, at slow blood flow rates (25-50 ml/minutes) and low transmembrane pressures (10-30 mm Hg), provided controlled removal of excess fluid. Although no major complications were encountered, hypothermia and hypotension (at ultrafiltrate flux rates exceeding 0.5 ml/kg/minute) were observed. The ultrafiltrate solute concentration was similar to plasma and no significant shifts in serum electrolytes were induced. The ultrafiltrate protein concentration of 64 to 2,760 mg/dl was much higher than previously reported.

Blood Flow Velocity↗

PubMed1979

[Hemodynamic changes during ultrafiltration and hemodialysis in uremia].

1. The ultrafiltration causes a reduction of blood pressure and minute output of the heart which is compensated by vasoconstriction and thus a decrease of blood pressure is prevented. 2. Changes in the salt concentrations with reduction of the osmolarity during the dialysis without simultaneous ultrafiltration lead to vasodilation and hypotension despite increase of the minute output of the heart. 3. During a usual haemodialysis (i.e. dialysis with simultaneous ultrafiltration) the vasodilating effect of the dialysis may abolish the vasoconstrictive effect of the ultrafiltration and thus may be the cause of the hypotension.

Adult↗

PubMed1978

Ultrafiltration without dialysis for removal of fluid and solutes in uremia.

A review is presented of the use of sequential ultrafiltration and dialysis to facilitate asymptomatic fluid removal in dialysis patiens, and the use of ultrafiltration as a method to remove uremic compounds. In sequential ultrafiltration and dialysis, the two physical principles in hemodialysis are separated in time. Hypotension and other side-effects which may be encountered when the two procedures take place simultaneously are eliminated or minimized by sequential treatment. Hemofiltration is an entirely new form of treatment, which mimics the performance of the human kidney better than hemodialysis. The blood is purified by ultrafiltration and fluid replacement either before or after the ultrafilter device. Preserved well-being or improvement in clinical condition have been reported after prolonged treatment with hemofiltration in spite of relatively inefficient elimination of small molecules as urea and creatinine. The most consistent beneficial effect of hemofiltration appears to be better blood pressure control in severely hypertensive patients than with conventional hemodialysis.

Humans↗

PubMed1978

Importance of the plasma refilling rate in the genesis of hypovolaemic hypotension during regular dialysis and controlled sequential ultrafiltration-haemodialysis.

The effects of ultrafiltration (UF) on plasma volume (PV) have been studied in eight patients using regular dialysis (RD) and controlled sequential ultrafiltration-haemodialysis (CSU) performed with a Rhodial 75 dialysis system. For a given value of UF the reduction of PV is determined by the plasma refilling rate. During CSU ultrafiltration induces a rapid increase in oncotic pressure without decreasing plasma osmolality. The high plasma refilling rate which can reach 1500 ml/hr allows moderate hypovolaemia despite high rates of UF and contributes to the usual good clinical tolerance of CSU. During RD a rapid decrease in plasma osmolality contributes to a water shift from the vascular space towards the interstitial and intracellular spaces and severe hypovolaemia can occur despite moderate ultrafiltration. CSU offers an adequate treatment for sodium overloaded patients with hypervolaemia, but is of no benefit in routine conditions.

Humans↗

PubMed1976

Anti-beta adrenoreceptor blockade activity of plasma ultrafiltrate in two uraemic patients: effect of parathyroidectomy.

A possible interaction between d-1 propranolol and hyperparathyroid plasma ultrafiltrate on guinea pig auricles has been studied in "in vitro" experiments. Plasma ultrafiltrates have been samples in two patients on chronci haemodialysis before (pre-PTx) and after (post-PTx) parathyroidectomy. A significant inhibition of propranolol depressant activity on cardiac contractile strength has been observed in the presence of pre-PTx plasma ultrafiltrates. On the contrary, no such inhibition was noted in the presence of post-PTx plasma ultrafiltrates.

Animals↗

PubMed1978

Bovine milk xanthine oxidase: purification by ultrafiltration and conventional methods which omit addition of proteases: some criteria for homogeneity of native xanthine oxidase.

Methodological difficulties have been encountered when proteases were omitted from the conventional isolation of bovine milk xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2). The use of these conventional methods has been studied and modified to reduce the problems encountered. Some of the difficulties may be due to the presence of high concentrations of caseins, which exhibit a wide range of charges and sizes, thereby making separations based on charge and size more complicated. In addition, non-covalent interactions may occur between the caseins and xanthine oxidase leading to the formation of casein-xanthine oxidase micellar aggregates. The difficulties encountered in this conventional isolation have been circumvented by purifying the enzyme directly from milk fat globule membranes that first have been washed free of most casein and other milk proteins. The xanthine oxidase is isolated by ultrafiltration through an Amicon XM-100A membrane at 5 degrees C in 0.25 M sucrose/5 mM sodium salicylate. The largest molecular size of globular proteins which can penetrate this ultrafiltration membrane has been previously estimated to be around 100 000 daltons. Xanthine oxidase thus appears to be smaller than 100 000 daltons in its native state. The size observed for active xanthine oxidase previously isolated by other methods has been around 275 000--300 000 daltons. Xanthine oxidase isolated by ultrafiltration appears similar to xanthine oxidase from conventional isolation methods according to empirical criteria of homogeneity based on size and also on the absorbances at 280 and 450 nm. Criteria based on charge were found to be less reliable.

Ammonium Sulfate↗

PubMed1977

The analysis of free tryptophan in human blood with the Ultrafiltrator: a comparison with other methods.

Recently, the Ultrafiltrator has been described, in the literature, which allows the ultrafiltration of small molecules in minute blood samples under anaerobic conditions with filters of any pore size. This apparatus has been tested for the separation of free tryptophan in heparinised and EDTA-plasma and in whole blood. At the same time, free tryptophan has been analysed after ultrafiltration with CF-50 A and CF-25 membrane cones (Centriflo). The results obtained by these two techniques are compared. Finally, a comprehensive review of other methods reported in the literature, concerning the isolation of free tryptophan, is presented.

Blood Proteins↗

PubMed1975

Inhibition of glyceraldehyde 3-phosphate dehydrogenase by plasma and serum ultrafiltrates due in part to a low-molecular-weight, nonpeptide material.

In an attempt to verify the existence in the blood of a diabetogenic peptide (somantin) derived from growth hormone, ultrafiltrates from plasma and serum from normal and diabetic subjects were prepared. The freeze-dried residues of these ultrafiltrates inhibited glyceraldehyde 3-phosphate dehydrogenase as somantin is claimed to do. However, the behavior of the inhibitory material on gel filtration on Sephadex G-10 indicated a molecular weight well below 700, rather than the considerably larger size claimed for somantin. The inhibitory material did not adsorb to Dowex 50W cation exchange resin at pH 2.5, while over 95 percent of ninhydrin-positive material was retained. Acid hydrolysis of the inhibitory material did not abolish its activity. Because of the presence of this low-molecular-weight, nonpeptide inhibitory material, inhibition of glyceraldehyde 3-phosphate dehydrogenase by a simple ultrafiltrate of plasma or serum is probably not a definitive measure of somantin.

Adult↗

PubMed1975

Cytotoxic effects on splenic ultrafiltrates upon leukaemic lymphocytes.

Ultrafiltrates from spleen inhibited both DNA synthesis and the proliferation of normal lymphocytes stimulated inculture from both mouse and man without apparent cytotoxicity. However, the same doses of this spleen ultrafiltrate will kill up to two-thirds of the leukaemic lymphoblasts from both mouse and man after 24 h incubation. This unique lymphocytotoxic effect could also be demonstrated on fresh primary cultures of leukaemic lymphocytes and was highly effective on slowly growing established cell lines under crowd culture conditions. Furthermore. ultrafiltrated thymus extract did not affect the DNA synthesis rates of the viability of NC-37 lymphoblasts, which have B cell characteristic. Thymus extract was cytotoxic to Molt cells, which have T cell characteristics.

Animals↗

PubMed1978

The accurate control of ultrafiltration.

An apparatus has been contructed to regulate ultrafiltration accurately during dialysis. The principle of the apparatus is that, per unit of time, exactly the same amount of dialysate is introduced into the dialyzer as is discharged from it. The apparatus consists of two isovolumetric pumps connected in line. The four compartments of the two pumps must change their functions at every pump stroke. This is a accomplished by a switching system. There is a continuously closed dialysate circuit. The fluid extracted from this circuit will be replenished from the blood compartment of the dialyzer. Ultrafiltration is regulated by a simple peristaltic pump, which sucks the fluid out of the closed dialysate circuit. The isovolumetric pumps and the switching system are driven by the elevated pressure of the dialysate (0.5--1.0 atm). The apparatus can be used in single pass dialysis. Dialysis in accordance with the Bergström principle can be simply performed. In over 5,000 dialyses with several types of dialyzers, ultrafiltration was always accurate within the measuring limits. Considerable improvement was noticed in the well-being of the patients; hypotension, nausea, vomiting and muscle cramps were not seen.

Body Fluids↗

PubMed1992

Net ultrafiltration in peritoneal dialysis: role of direct fluid absorption into peritoneal tissue.

'Net ultrafiltration' in peritoneal dialysis refers to the difference between the osmotically induced ultrafiltration into the peritoneal cavity and the fluid loss from the cavity during dialysis. Recent research has demonstrated that, during a 3- to 4-hour experimental dialysis, 5-25% of the total fluid loss is via lymphatics and the remaining fluid is absorbed directly into the tissue surrounding the peritoneal cavity. The driving force for this convection into tissue is the hydrostatic pressure gradient between the peritoneal cavity and the tissue, which ranges from 2 to 8 mm Hg during the typical 2-liter dialysis in humans. Because the convection from the cavity occurs during periods of a positive net ultrafiltration, the peritoneum and its underlying tissue cannot be represented as a single membrane but function as a composite of 'tight' and 'loose' membranes. More data on the mechanical properties of the peritoneal tissue space and its response to hydrostatic pressure in the cavity are required before we fully understand fluid transport at the tissue level.

Absorption↗

PubMed1978

Effects of ultrafiltration of diffusion and convection in two newer coils.

Clearances of sodium and B12 were measured with increasing ultrafiltration in two newer coils with new types of membrane support. In all other coil studies previously reported, clearance increases with ultrafiltration did not equal predictions from contributions of convection implying simultaneous decreases in diffusive solute transport with increasing transmembrane pressure. Such deterioration was attributed to masking of membrane surface area by the membrane support, widening of blood channels, and/or channeling of dialysate flow. In these newer coils, clearance increases were very near to predicted enhancement by convection while diffusion was stable in one type and decreased only modestly in the other. Coil volumes assessed with the kerosene technique increased with higher transmembrane pressure similar to findings in previous coils studies. Thus, although coil blood path dimensions are altered with increasing pressure as in older coils, diffusive clearances remain stable and increases in total clearances equal that predicted from convective solute transport. These results suggest that membrane masking is probably the major mechanism for decreases in diffusion with ultrafiltration in other coils and that the problem has been minimized with improved membrane supports.

Chemical Phenomena↗

PubMed1977

Clinical evaluation of the clearance profiles of a portable, compact, dialysate-free system incorporating microencapsulated charcoal hemoperfusion for blood purification with ultrafiltration for fluid removal.

A total of 30 procedures have been carried out in two patients using a new portable, compact, dialysate-free system formed by combining 300 gms of albumin--cellulose nitrate microencapsulated activated charcoal (ACAC) in series with a small Amicon ultrafiltrator. Blood passing through the ACAC hemoperfusion system is purified of waste metabolites and toxins. Fluid removal is carried out with the hydrostatic pressure of the blood passing through the dialysate-free ultrafiltrator. Since ACAC hemoperfusion is much more efficient than hemodialysers for blood purification, the combined system with the ultrafiltrator results in a very efficient system for blood purification and fluid removal. Typical clearance data for the combined systems include: 75 ml/min for 2000--5000 MW; 112.7 ml/min for 300--1500 MW; 235 ml/min for creatinine; 240 ml/min for uric acid; 2500--2700 ml/2 hours for water removal; and 17--18 gm/2 hours for NaCl removal. Guanidines, mercaptans, and PTH are also cleared very efficiently.

Charcoal↗

PubMed1979

Hemodynamics during hemodialysis, sequential ultrafiltration and hemofiltration.

Circulatory parameters were determined by cardiac catheterization in patients on maintenance hemodialysis. They were studied in three groups during conventional hemodialysis, sequential ultrafiltration and hemofiltration. All three groups revealed significant reduction of cardiac output, stroke volume, pulmonary artery pressure and plasma volume. In the hemodialysis group hemodynamic parameters were unstable; specifically, hypotension, increased heart rate, and only minimal increase of peripheral resistance were observed. The other two groups showed only minor changes in circulatory parameters despite high ultrafiltration rates. Blood pressure and heart rate remained stable. On the other hand, peripheral vascular resistance increased remarkably. There is compelling evidence that during hemofiltration and sequential ultrafiltration, the patient's ability for vasoconstrictive counterregulation is better maintained than during conventional hemodialysis.

Blood Pressure↗

PubMed1976

[Peritoneal dialysis, ultrafiltration and hyperosmolarity].

Observation of a patient who developed serious hypernatremia during peritoneal dialysis with a dialysis fluid containing 135 mval Na+/1 prompted investigation of net water, sodium, potassium and chloride transport during 45 peritoneal fluid exchanges with standard dialysis solutions containing 1.5 and 4.5 g% glucose. With both solutions and an equilibration time of 0 min, net ultrafiltration was observed (89 ml and 230 ml per exchange respectively). In both groups the calculated sodium concentration of the ultrafiltrate was considerably lower than plasma sodium concentrations (27.0 mval/1 and 36.9 mval/1 respectively, resulting in a new sieving coefficient of 0.20 and 0.27 respectively. Therefore, the free water deficit resulting from peritoneal ultrafiltration is directly responsible for the hypernatremia observed during peritoneal dislysis. While the potassium and chloride transport observed in these studies can be explained by diffusion processes along a given concentration gradient, sodium transport and sodium concentrations raise the question of more complex mechanisms. The data are discussed with reference to the relative significance of diffusion processes versus bulk flow and solvent drag.

Biological Transport↗

PubMedDate not supplied

[Study of ultrafiltration of trypsin solutions].

The dependence of the rate of trypsin ultrafiltration on the concentration, pressure and structure of membranes was studied. During ultrafiltration of diluted trypsin (0.3 mg/ml), water and sodium chloride the flow rate increased linearly with a pressure increase in the range of 0.4-4.2 kg/cm2. During ultrafiltration of trypsin solutions of a concentration of 1 mg/ml and over at a pressure of 2-3 kg/cm2 deviations from linear proportionality occurred which enhanced with an increase in the protein concentration and a decrease in membrane permeability.

Binding Sites↗