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Biomedical subjects

A Válek

Publications and source records attributed to A Válek.

At least 19 recordsLinked to original sources
PubMed1995

Influence of the dialyzer membrane material on sodium transport in hemodialysis.

Traditionally Gibbs-Donnan coefficients based on the mean charge of plasma proteins are used as the only correction factor in equations describing sodium transport across the dialyzer membrane. This ignores the possible impact of the membrane material. Correction coefficients (CC) of the whole dialyzer were measured during in vivo dialysis as a quotient of dialysate to plasma sodium in an equilibrated state for different membrane materials used in commercially available dialyzers. Their mean value and correlation with total plasma protein content (TPP) were evaluated. CC for the six materials evaluated differed both in the intercept and slope of the regression line CC versus TPP: Cuprophan 1: CC = 1.0253 - 0.00017 x TPP; Hemophan 1: CC = 1.119 - 0.00175 x TPP; Hemophan 2: CC = 1.095 - 0.00111 x TPP; PMMA: CC = 1.0353 - 0.00044 x TPP; SCE:CC = 1.114 - 0.00145 x TPP; and Cuprophan 1:CC = 1.0562 - 0.00065 x TPP. The observed differences are attributed to the different charge densities of the membrane materials and suggest that for a precise description of sodium transport, the role of the membrane material needs to be considered.

Blood Proteins↗
PubMed1995

Analysis of the urea generation rate and the protein catabolic rate in hemodialyzed patients.

The urea generation rate (G) and the protein catabolic rate (PCR) have been investigated in two groups of hemodialyzed patients over a whole week cycle, one with zero residual renal function (Kr = 0) dialyzed thrice weekly and the other dialyzed twice weekly with nonzero residual renal function. The two-pool model of urea kinetics was used. No relationship between patients' age and the PCR was found, and also no difference in the PCR between males and females was seen. All patients with a PCR < 0.8 g/kg/day had a midweek predialysis plasma urea level well below 25 mmol/L, which clearly documents the value of a kinetic approach in early detection of patients at risk for malnutrition. In the thrice weekly dialyzed group, a statistically significant relationship was found between PCR and KT/V:PCR = 0.582 + 0.253 x KT/V, r = 0.374 with p < 0.05. In the twice weekly dialyzed group with nonzero Kr, contribution of the residual renal function had to be included into KT/V to reach a level of statistical significance of PCR = 0.697 + 0.18 x KT/V, r = 0.481 with p < 0.05. With regard to values of Kr encountered in the investigated group (0-3.5 ml/min), its influence upon PCR is higher than a volumetrically equal increase in excretorial efficacy of the artificial kidney. The G in the thrice weekly dialyzed group was found to be dependent on the length of the interdialytic interval over which it was evaluated. Over the intervals Friday-Monday, Monday-Wednesday, and Wednesday-Friday the following mean values of G were obtained: 0.155, 0.180, and 0.188 mmol/min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclic AMP Receptor Protein↗
PubMed1993

Clinical study of high-flux cuprammonium rayon hemodialysis membranes.

The aim of this crossover clinical study was to gain basic information on the hemocompatibility and effectiveness of recently developed high-flux membranes made of cuprammonium rayon with ultrafiltration coefficients of 10, 17, and 19 ml/mm Hg/h (S12W, SU12W, and SS12W dialyzers, respectively), and to identify any possible differences from a conventional membrane made of the same material with an ultrafiltration coefficient of 6 ml/mm Hg/h (C12W dialyzer). All the tested membranes led to an abrupt drop in leukocyte count in the initial phase of hemodialysis. In high-flux membranes, C5a anaphylatoxin would pass into the dialysate, but mean C5a anaphylatoxin concentrations in the dialysate were lower by orders of magnitude than its plasma concentrations, which behaved, in high- and low-flux membranes alike, typically of those made of nonsubstituted cellulose with no intermembrane differences. As judged by the concentrations of the thrombin-antithrombin III complex, the coagulation system was activated--again, without differences between membranes. The reduction rates for urea, creatinine, and phosphates were comparable for all the tested membranes. Compared with baseline, the post-dialysis serum concentrations of beta 2-microglobulin in high-flux membranes, unlike the low-flux membrane, were significantly lower. We conclude that there are no significant differences between the tested high- and low-flux membranes made of cuprammonium rayon in the monitored hemocompatibility parameters, and that high-flux membranes are capable of reducing serum beta 2-microglobulin concentrations.

Adult↗
PubMed1992

[Clinical study of biocompatibility of dialysis membranes made from non-modified and modified cellulose].

Basic biocompatibility parameters of dialysis membranes made of non-substituted regenerated cellulose (NRC) and cellulose membranes with hydroxyl groups substituted, to a higher (H) or lower (L) degree, by dl-ethyl-amino-ethyl groups (DEAE), or by acetate (CA) were investigated in a 16-week clinical study, involving 10 long-term haemodialysis patients. In the 15th minute of dialysis, the decrease in blood leukocyte count, while using NRC (0.24 +/- 0.03 of baseline value, arithmetic mean +/- SEM) was deeper compared with that seen in DEAE-L (0.88 +/- 0.10, p < 0.001), in DEAE-H (0.79 +/- 0.10, p < 0.01), and in CA (0.73 +/- 0.05. p < 0.05). In the 15th minute of the procedure, C5a concentrations, reflecting complement activation, were higher in NRC (4.4 +/- 0.51 micrograms/L) than in DEAE-L (1.41 +/- 0.22, p < 0.001), in DEAE-H (1.68 +/- 0.47, p < 0.01), and in CA (1.68 +/- 0.22, p < 0.01). Activated clotting times were, in the 10th minute of the procedure, significantly longer in NRC (2.94 +/- 0.37 of baseline value) than in DEAE-H (1.74 +/- 0.10, p < 0.05) and, by the end of dialysis, the difference between these membranes (NRC: 1.47 +/- 0.21, DEAE-H: 0.85 +/- 0.08, p = 0.07) was close to the level of statistical significance. The authors conclude: 1. Substitution of the hydroxyl groups of regenerated cellulose reduces the decrease in leukocyte count and complement activation in the initial phase of haemodialysis. 2. At the same time, substitution by DEAE groups may raise thrombogenicity, as indicated by the shorter activated clotting times.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[14 years of the peritoneal dialysis program at the internal medicine department in Strahov (1978-1991)].

The authors present an account of 14 years experience of the department as regards treatment of chronic renal failure by peritoneal dialysis. Initial experience revealed that this method is feasible as an alternative of haemodialyzation treatment even in case of limited technical possibilities (using the so-called bottle system) but treatment was associated with a high incidence of peritonitis. During the subsequent period the incidence of peritonitis was substantially reduced in conjunction with the elaboration of hygienic provisions, enlightment of patients and a change from the regime of continual exchanges in a home environment to a regime of intermittent peritoneal dialysis performed mostly in hospital. Experience assembled in the department was also important. The longest period of treatment is 60 months. In another 18 patients it is more than 20 months. The most frequent cause of termination is loss of the ultrafiltration capacity of the peritoneum. Several patients had successful transplantations. The prolonged experience can be used at present when the so-called bag system is introduced.

Adult↗
PubMed1992

[Does therapeutic membrane plasmapheresis increase protein synthesis?].

The objective of the investigation was to assess whether therapeutic membrane plasmapheresis accelerates protein synthesis. To this end pseudouridine (PSI), a modified nucleoside was investigated which provides information on the tRNA turnover and thus indirectly also on protein synthesis. The authors made 10 plasmapheresis on a A 2008 PF monitor with Plasmaflux P2 filters which they use to exchange 1 plasma volume of the patients. Laboratory indicators were investigated one day before plasmapheresis, on the day of plasmapheresis and during its course, and on the 1st, 2nd and possibly 3rd day after plasmapheresis. They revealed that the clearance of the plasma filter for PSI (0.41 +/- 0.04 ml/s, arithmetical mean +/- SEM) did not differ significantly from the filtration rate (0.49 +/- 0.01 ml/s, p = 0.15). As compared with the initial examination (0.49 +/- 0.06 ml/s) on the first day after plasmapheresis as a result of reduced glomerular filtration rate the renal clearance of PSI was reduced (0.33 +/- 0.05, p less than 0.01). PSI serum concentrations were therefore expressed as the serum PSI/serum creatinine ratio. This ratio was, as compared with the initial examination (80.4 +/- 4.8 nmol/mumol), raised midway during the procedure (100.8 +/- 8.6, p much less than 0.05) and after its termination (132.3 +/- 6.1, p much less than 0.01). The increase was not due to disintegration of cells or dietary factors. The rise of the serum PSI/serum creatinine ratio was due to a more rapid tRNA turnover and thus provided evidence that therapeutic membrane plasmapheresis accelerates protein synthesis.

Humans↗
PubMed1992

An equation for calculating postdialysis plasma sodium.

Well defined dry weight is a must for adequate UF control during haemodialysis (HD). However, interdialytic weight gain (delta BW) must not be excessive. delta BW is closely related to interdialytic thirst which in turn is strongly influenced by post-dialysis plasma sodium (CPNa post), but little is known about the desired CPNa post. The points below serve as a basis for establishing this value. a) Thirst is mediated by osmoreceptors. b) A strong correlation has been found between delta BW and intradialytic increase in plasma sodium but no such correlation exists with the interdialytic increase in plasma urea. This indicates that fluid intake between dialyses depends solely on electrolytes. c) Pre-dialysis plasma sodium in an individual is stable, indicating that the patient is at his "set value" of electrolyte osmolality. d) Half of the potassium removed during HD comes from the extra- and half from the intracellular space. Assuming that it is desirable not to disturb a patient's pre-dialysis osmotic steady state, it can be calculated that the desired CPNa post should be higher than the pre-dialysis value by half of the intradialytic plasma potassium drop, i.e., approx. CPNa post = CPNa pre + 1 to 2 mmol/l.

Humans↗
PubMed1991

What are the factors contributing to the changes in tissue-type plasminogen activator during haemodialysis?

Haemodialysis (HD) is associated with stimulation of the fibrinolytic system. The increase of fibrinolytic activity seems to be primarily due to tissue-type plasminogen activator (t-PA) released from the vessel wall. The aim of our study was to determine whether the t-PA release is the consequence of uraemic intoxication adjustment, extracorporeal circulation effect, heparin administration, or whether a mere reflection of the circadian rhythm of fibrinolysis is involved. To identify the factor, fibrinolytic system parameters were determined during HD, sham HD (SD), after the administration of heparin alone outside HD, and during a control period (CP). The plasma concentrations of t-PA antigen indicate that HD is associated with the release of t-PA from the vessel wall; 3.70 ng/ml before HD, 4.35 (NS) at the 15th min, 4.88 (P less than 0.05) at the 20th min, and 5.09 (P less than 0.05) after HD (medians). The respective values for a CP are 4.05, 4.37 (NS), 4.40 (NS), and 4.22 (NS). The effect of heparin alone and SD was evaluated for 120 min only, with the following t-PA concentrations determined after heparin: 5.10, 6.22 (NS), 4.72 (NS), 4.72 (NS); during SD and 4.50, 5.14 (NS), 5.20 (P less than 0.05). We conclude that t-PA is released from the vessel wall during HD. A factor contributing to its release is the extracorporeal circulation system.

Adult↗
PubMed1991

Haemofiltration or haemodialysis in aluminium elimination?

Elimination of aluminium from the body during haemodialysis and haemofiltration was investigated. Without desferrioxamine administration there was no aluminium removal from the body. After DFO administration (1 g intravenously 24-40 h before dialysis or haemofiltration) removal of aluminium during blood purification methods was achieved. During haemodialysis (n = 28, cuprophane plate dialyser with urea clearance 150 ml/min, 5 h) serum aluminium decreased by 41%. Aluminium clearance was 28 ml/min. During haemofiltration (n = 36, polyamide FH 77, volume exchange 60% of body-weight, on-line system) serum aluminium decreased by 66% and a total of 1962 micrograms of aluminium was removed during one procedure. In the 60th minute of the procedure, calculated clearance was 42 mmol/l. Because of the rebound phenomenon it is reasonable to perform two haemofiltrations after a single dose of DFO. Haemofiltration is superior to haemodialysis in aluminium removal from the body.

Aluminum↗
PubMed1990

[The effect of 1,25-dihydroxycholecalciferol on immunity and the clinical state and on parameters of phospho-calcium metabolism in dialyzed patients].

Sixteen months of administration of 1,25-dihydroxycalciferol (Rocaltrol) to twelve patients with chronic renal failure led to a substantial reduction of infectious complications during the investigation period and to improvement of the clinical condition of the patients evaluated with regard to bone and muscle pain. In laboratory indicators of immunity the authors observed an increase of the originally reduced values of phagocytosis of C, albicans and candidacidal after two weeks' administration of the drugs. Changes in the ratio of sub-populations of lymphocytes were apparent also after 16 months therapy: the authors observed a continuous decline of the lymphocyte B and lymphocyte T4 ratio and rise of the cytotoxic suppressor fraction CD8+ of lymphocytes. The different trend of changes of some immunological, biochemical and clinical indicators was apparent when the patients were subdivided according to the aetiology of renal failure.

Adult↗
PubMed1990

[Comparison of the effectiveness of hemodialysis and hemofiltration in the removal of aluminum from the body].

The authors compare the excretion of aluminium from the organism of patients with chronic renal failure during haemodialysis and haemofiltration. Aluminium can be eliminated from the organism only after previous administration of Desferal. Haemodialysis and haemofiltration alone practically do not eliminate aluminium from the organism. During haemodialysis made 24-40 hours after administration of 1 g Desferal (24 procedures, cuprophan plate dialyzer Chiraplat, urea clearance 2.5 ml/s, time 5 hours) the Al serum concentration declined by 41% and the dialyzer clearance for aluminium was during the 60th minute of haemodialysis 0.47 ml/s. During haemofiltration made 24-40 hours after administration of 1 g Desferal (36 procedures, polyamide haemofilter FH 77 on-line system of fluid exchange = 60% body weight) the Al serum concentration declined by 66% and the clearance of the haemofilter for Al was during the 60th minute 0.70 ml/s. Contrary to haemodialyzation treatment of Al intoxication, treatment with haemofiltrations was not associated with clinical complications. Haemofiltration treatment is a safe and effective method for the treatment of Al intoxication and accumulation in patients with chronic renal failure.

Aluminum↗
PubMed1990

Beta 2-microglobulin serum levels during dialysis: effect of cuprophan and serum osmolality changes.

New cuprophan dialysers were used in twenty, re-used dialysers in twelve dialyses and new dialysers in ten sequential ultrafiltrations. Serum beta 2-microglobulin (beta 2m) concentration was measured before and after all these procedures. Serum osmolality changes were compared with changes in serum beta 2m concentrations. These concentrations rose in dialyses with new and re-used dialysers, but remained unchanged during sequential ultrafiltration. beta 2m increased with serum hypo-osmolality, decreased with serum hyperosmolality and did not change during iso-osmolar dialysis. These results indicate that cuprophan membrane does not raise beta 2m concentration during dialysis. It is hypo-osmolality that is responsible for the increment of beta 2m in serum.

Cellulose↗