Acetate-free Biofiltration Research Articles

Plasma advanced glycosylation end-products in maintenance haemodialysis patients

Pentosidine is a useful marker of advanced glycation end-products (AGE) which form cross-links between proteins and have been found elevated in plasma and tissues of uraemic and haemodialysed subjects. The origin and fate of these molecules are not clearly understood, but they might play a role in the cardiovascular complications of end stage renal failure. The aim of this study was to evaluate the effect of different types of substitutive therapy on the removal of pentosidine. Pentosidine was measured by a two-step HPLC methodology. Its concentration was evaluated in plasma before and after dialysis session, in 24-h urine, and in dialysate of subjects treated with three types of chronic substitutive therapy: bicarbonate haemodialysis, acetate-free biofiltration, and haemofiltration. Pentosidine levels were compared among the three therapy modalities and correlated with clinical and biochemical parameters. Plasma pentosidine level was extremely high (23.7 +/- 2.0 pmol/mg protein) in the patients treated with the different dialysis modalities. The dialysis session had no significant effect on its plasma concentration, but haemofiltration seemed to be the most efficient method (300-2000 nmol of pentosidine removed per session versus 250-700 nmol per session with the two other approaches). An interesting correlation was found between pentosidine and blood urea nitrogen (r = 0.58, P < 0.01) and pentosidine with uric acid (r = 0.48, P < 0.05). These results suggest that none of the methodology showed a good removal of pentosidine, but among them haemofiltration has the best efficiency. The statistical relationships between pentosidine and urea and uric acid respectively might provide insight into the origin of pentosidine. The accumulation of reactive AGE in uraemic patients may be implicated in the organ and tissue damage observed in uraemia.

Clinical observation and nutritional assessment in biofiltration without acetate: three years experience in elderly patients

Acetate free biofiltration (AFB) has been proposed as an alternative method to standard hemodialysis for patients with acetate intolerance, cardiovascular instability and severe metabolic acidosis. Aim of the study is to retrospectively analyze the prevalence of morbidity and mortality in a population of elderly patients treated with AFB (3 and a half hours session).

Correction of chronic metabolic acidosis in haemodialysed patients by acetate-free biofiltration does not influence parathyroid function

In eight patients remaining acidotic after more than 1 year of bicarbonate haemodialysis, we studied the effect of correcting the chronic metabolic acidosis using acetate-free biofiltration for 4 months on the course of secondary hyperparathyroidism. An AN69 capillary membrane was employed with a bicarbonate infusion rate initially set at 1.8 l/h in all patients and then adjusted in each one to obtain a predialysis bicarbonate of > or = 23 mmol/l. Standard blood chemistry parameters were determined every 2 weeks. Measurements of PTH, calcifediol and calcitriol, as well as calcium-PTH curves were determined at the beginning and end of the study. While acetate-free biofiltration appears to be an adequate technique for the correction of chronic metabolic acidosis when bicarbonate dialysis fails, this study indicates that it does not influence secondary hyperparathyroidism in haemodialysed patients. The level of intact PTH did not vary significantly and the calcium-PTH curves at 0 and 4 months were superimposable with no significant differences in the set point and the slope of the curves.

Paediatric experience with acetate-free biofiltration.

We describe our preliminary experience with five children who received acetate-free biofiltration, a modification of haemodiafiltration without buffer in the dialysate and simultaneous infusion of bicarbonate through a venous port. Adequacy of haemodialysis (HD) was achieved with 3 h treatments three times per week (mean Kt/v 1.35 +/- 0.29, mean protein catabolic rate (PCR) 1.4 +/- 0.3 mg/dl). During the session, pH increased from 7.4 pre HD to 7.5 post HD. The mean bicarbonate infused as a 0.166 M solution averaged 235 +/- 35 mEq/h. Hypertension did not occur. There were no cramps, hypotension or vomiting. Bicarbonate requirements correlated significantly with dialyser surface area and body weight (r = 0.76, P < 0.001).

Our Experience with Acetate-Free Biofiltration

Our Experience with Acetate-Free Biofiltration

A scheme for acetate-free biofiltration and programmable hemodialysis

A scheme for acetate-free biofiltration and programmable hemodialysis

The Plasma Glutathione Peroxidase Enzyme in Hemodialyzed Subjects

The kidney is probably the major site of production of the plasma enzyme glutathione peroxidase (GSHPx-P). For this study, GSHPx-P activity was determined in 40 healthy people, in 34 patients with differing degrees of renal impairment, and in hemodialysis patients from whom blood samples were withdrawn either before or after each session (18 patients) or throughout the dialysis session (27 patients). Hemodialysis patients were treated by means of different techniques (bicarbonate hemodialysis, hemodiafiltration, and acetate free biofiltration), and different membranes (cuprophane, polyacrylonitrite, and polymethylmethacrylate). The following results were obtained: 1) GSHPx-P activity was significantly decreased in renal impairment patients; 2) GSHPx-P activity negatively correlated with serum creatinine values in renal impairment patients (r= −0.55; p < 0.001); and 3) the enzyme activity slightly increased after the session in hemodialysis patients. The following conclusions can be drawn: GSHPx-P activity could be a new index of renal function, because it was decreased in patients with renal failure; the decrease in GSHPx-P activity paralleled the severity of renal impairment, and was maximal in hemodialysis patients; GSHPx-P activity was slightly raised at the end of the hemodialysis session, concomitant with other enzyme activities (aspartate transaminase, alanine transaminase, and alkaline phosphatase) and total protein concentration. This seems to be attributable to the process of water loss rather than other hypothetical mechanisms, such as A) enzyme activation by either peroxide generation during blood-membrane contact, or by the removal of a hypothetical inhibitor; and B)de novosynthesis in the residual renal mass or in other sites of production.ASAIO Journal1994; 40:968-971.

The Plasma Glutathione Peroxidase Enzyme in Hemodialyzed Subjects

The kidney is probably the major site of production of the plasma enzyme glutathione peroxidase (GSHPx-P). For this study, GSHPx-P activity was determined in 40 healthy people, in 34 patients with differing degrees of renal impairment, and in hemodialysis patients from whom blood samples were withdrawn either before or after each session (18 patients) or throughout the dialysis session (27 patients). Hemodialysis patients were treated by means of different techniques (bicarbonate hemodialysis, hemodiafiltration, and acetate free biofiltration), and different membranes (cuprophane, polyacrylonitrite, and polymethylmethacrylate). The following results were obtained: 1) GSHPx-P activity was significantly decreased in renal impairment patients; 2) GSHPx-P activity negatively correlated with serum creatinine values in renal impairment patients (r = -0.55; p < 0.001); and 3) the enzyme activity slightly increased after the session in hemodialysis patients. The following conclusions can be drawn: GSHPx-P activity could be new index of renal function, because it was decreased in patients with renal failure; the decrease in GSHPx-P activity paralleled the severity of renal impairment, and was maximal in hemodialysis patients; GSHPx-P activity was slightly raised at the end of the hemodialysis session, concomitant with other enzyme activities (aspartate transaminase, alanine transaminase, and alkaline phosphatase) and total protein concentration. This seems to be attributable to the process of water loss rather than other hypothetical mechanisms, such as A) enzyme activation by either peroxide generation during blood-membrane contact, or by the removal of a hypothetical inhibitor; and B) de novo synthesis in the residual renal mass or in other sites of production.

Calcium Mass Balance and Behavior of Intact Immunoreactive Parathyroid Hormone in Acetate-Free Biofiltration: Acute and One-Year Evaluation

The present study evaluated calcium mass balance (MB) during acetate-free biofiltration (AFB) with a dialysate calcium concentration of 2 mmol/l and different ultrafiltration rates (UF; 42.5 ml/min in schedule 1 and 48.5 ml/min in schedule 3), and with a calcium concentration of 1.75 mmol/l but an UF of 43 ml/min (schedule 2). We also examined the effects of these schedules on the behavior of intact parathyroid hormone (I-PTH). AFB according to schedule 1 and 3 achieve a positive calcium MB (8.49 +/- 1.56 and 5.59 +/- 1.06 mmol, respectively), while in schedule 2 calcium MB merely balanced (0.07 +/- 2.29 mmol/l). A significant acute intradialytic I-PTH decrease was observed with all schedules; after 1 month, however, predialytic PTH values were unchanged in schedules 1 and 3, but worsening was noted in schedule 2. Subsequently, AFB was performed for 12 months employing a dialytic schedule (No. 1) involving a positive calcium balance. A year later I-PTH was significantly lower, thus proving that AFB may play an additional part in controlling secondary hyperparathyroidism.

High- and low-flux acetate-free biofiltration: experimental assessment of calcium mass balance and intact parathyroid hormone behaviour

We studied total calcium mass balance and plasma intact parathyroid hormone behaviour in 10 uraemic patients who underwent acetate-free biofiltration carried out in accordance with six different dialytic schedules, where either a polyacrylonitrile or a polysulphone membrane was used. Schedules 1 and 2 involved a reinfusion flow rate of 33.3 ml/min with a dialysate calcium concentration (DCa) of 1.75 and 2 mmol/l respectively; in schedule 3, 4, 5 and 6 reinfusion flow rate amounted to 50 ml/min and DCa was respectively of 1.75, 2, 2.25 and 2.5 mmol/l. Dehydration remained unchanged in all schedules: 700 g/h. Finally high- and low-flux acetate-free biofiltration are able to induce different Ca mass balance which may suit different therapeutic contexts. Ca mass balance was either positive or negative depending on reinfusion flow rate and DCa. With a reinfusion flow rate of 33.3 ml/min a DCa of at least 2 mmol/l was necessary to obtain a positive mass balance, while with a reinfusion flow rate of 50 ml/min DCa had to equal 2.25 mmol/l. In high-flux acetate-free biofiltration, the estimation of predialytic Ca2+ and DCa values, using a simple formula, allows prediction of the mass balance that will be attained. At the end of acetate-free biofiltration, intact parathyroid hormone always decreased when a polyacrylonitrile membrane was employed while it increased, in the presence of negative Ca mass balance with a polysulphone membrane.

Acetate‐Free Biofiltration in Acute Renal Failure

Hemodialysis treatment for acute renal failure is associated with a high incidence of adverse reactions. Hemodynamic stability and adequate correction of acid-base and hydroelectrolyte imbalance are the main goals of dialytic strategy in acute renal failure. However, the variety of etiology and the diversity of clinical conditions suggest that individualized treatment may be advisable. To this purpose, in 26 patients suffering from "isolated" acute renal failure of different etiologies, we have used acetate-free biofiltration. We have performed 411 dialyses with an extremely low incidence of symptomatic treatments and remarkable cardiovascular stability. Correction of fluid, electrolyte, and acid-base imbalance proved excellent. Dialytic efficacy proved adequate. Our data show that acetate-free biofiltration is an easy technique suitable for individualized treatment and adaptable to changing needs during hemodialysis in patients with isolated acute renal failure.

Correction of a metabolic alkalosis induced by lemon consumption by acetate-free biofiltration

Correction of a metabolic alkalosis induced by lemon consumption by acetate-free biofiltration

Plasma lipids and fatty acid levels in chronically uremic patients undergoing blood purification with different methods.

Levels of plasma lipids and the fatty acid composition of major plasma lipid classes have been determined in chronically uremic patients before and after treatments with hemofiltration, high efficiency paired filtration dialysis, or acetate-free biofiltration. The major findings are a decrease of triglycerides and an increase of total free fatty acids (FFAs) at the end of the dialytic session--already reported in the literature--that do not appear to be strictly dependent on heparin administration. The changes in the plasma concentrations of selected saturated and polyunsaturated fatty acids, which may contribute to alteration of functional parameters in the cardiovascular system in dialyzed patients, are different in the various types of techniques.

Acetate Free Biofiltration

Acetate free biofiltration (AFB), a new hemodiafiltration (HDF) technique characterized by a buffer free dialysate and postdilution infusion of a sterile HCO3 solution, was recently proposed as an alternative to HDF performed with acetate or bicarbonate dialysate. To evaluate the effects of dialysate buffer on immune cell activation, release of interleukin-1 (IL-1), tumor necrosis factor (TNF), prostaglandin E2 (PGE2), and leukotriene B4 (LTB4) from peripheral blood monocytes was studied in 12 uremic patients before and after HDF with polyacrylonitrile membranes (Filtral 12, Hospal Laboratories, Bologna, Italy) and consecutive dialysis with acetate, bicarbonate, and AFB. Data were correlated with the monocyte cytoplasmic concentration of Ca++, an index of early cell activation. Levels of bacterial endotoxins in the acetate, bicarbonate, buffer free dialysate, and infusate for AFB were also determined. Results showed that release of IL-1, PGE2, and LTB4, was greater after HDF with acetate than with bicarbonate; after bicarbonate dialysis, however, TNF production was significantly higher. On the other hand, after AFB, minimal production of these cytokines was seen and TNF, in particular, was undetectable. There was a direct correlation between release of cytokines in the monocytes and cytoplasmic Ca++ content. In the bicarbonate dialysate, detectable levels of bacterial endotoxins were found, whereas the acetate, buffer free dialysate, and infusate were endotoxin free. It was concluded that acetate dialysis directly activates peripheral blood monocytes to produce IL-1, PGE2, and LTB4, whereas bicarbonate induced TNF activation occurs through endotoxins. In AFB, which uses a buffer free dialysate and sterile bicarbonate infusion, monocyte activation is negligible.

Sodium modeling in hemodiafiltration

A computer model was developed to simulate sodium and water kinetics during hemodiafiltration (HDF), acetate-free biofiltration (AFB) and hemodialysis (HD). Multiple regression analysis of the results of 3,240 simulated applications of the model (1,620 HDF, 1,080 AFB, 540 HD) showed that, during HDF and AFB, there is a close correlation (R2 = 0.92 and 0.91) between plasma water sodium concentration [( Na+P]) and a set of three variables: 1) the sodium gradient between plasma water and dialysate, 2) the sodium concentration of the substitution fluid and 3) ultrafiltration (UF) rate. With HD, a close correlation (R2 = 0.94) was found between changes in [Na+P] and combined changes in sodium gradient and the UF rate. On this basis, a regression equation was formulated for each procedure which allowed a reliable prediction of final [Na+P] to be made on the basis of knowledge of the imposed Na gradient, the programmed infusion (during HDF and AFB), and the UF rate. Clinical validation of the model was obtained in 12 patients: predicted final [Na+P] agreed well with the values measured by means of direct potentiometry (141.9 vs. 142.1 mEq/liter; P = NS), with a mean difference (-0.16 mEq/liter) and limits of agreement (+0.8 to -1.03 mEq/liter) fully acceptable for clinical purposes.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphate kinetics in acetate-free biofiltration.

The phosphate kinetics during bicarbonate dialysis (BCD) and Acetate-free Biofiltration (AFB) were determined in 3 stable regular dialysis patients. These patients were switched to a 6-month period of AFB after a 12-month period of BCD. The plasma levels of phosphate, urea, and bicarbonate, and mass removal of phosphate and urea were measured every hour, during 3 consecutive dialysis sessions on BCD and AFB. The plasma phosphate behavior revealed a peculiar form with two main components, which differed from that of urea. The plasma phosphate level fell sharply during the first 2 hours of treatment, and then remained at a plateau towards to the end of the session. The plasma bicarbonate levels during the treatment sessions in the case of AFB were significantly higher than that in BCD. The actual mass removal in AFB was similar to that BCD, despite a significantly lower value of pre-plasma phosphate. A high ultrafiltration rate and better control of acidosis might be the reason for the better performance of phosphate mass removal in AFB. Better control of phosphatemia due to AFB can lead to a reduction in the amount of phosphate binders which have several untoward side effects.

Forecasting Correct Sodium Balance in Hemodiafiltration Procedures Involving Infusions

Four patients, stable on acetate hemodialysis (AHD), were switched to acetate-free biofiltration (AFB) which differs from AHD and bicarbonate hemodialysis (BHD) in that the dialysate contains no buffer, which is given intravenously as a hypertonic (1/6 M) Na bicarbonate solution. Within the 1st month the patients developed thirst and hypertension attributed to a positive Na balance. The aim of this investigation was to check this (1) by a study based on the predictable changes induced in the body compartments of 13 patients by the infusion and ultrafiltration (UF) of a hypertonic solution and (2) by direct determination and calculation of 28 Na mass balances in BHD and AFB. The theoretical model indicated that infusion of 4.87 liters of a 166.7 mEq/l Na bicarbonate solution and UF of the same amount caused a positive balance of 233 mosm of Na. The Na mass balances showed a relationship between Na transmembrane gradient and loss or gain of Na in both methods (p less than 0.0001). The slopes of the regression lines were not significantly different but there was a highly significant difference between the y axis intercepts (p less than 0.0001), which indicates that the same Na transmembrane gradient that gives no net change of Na in BHD, induces a net gain of 240 mosm (120 mEq of Na) in AFB and that to obtain the same Na balance dialysate Na should be reduced by about 8 mEq/l in AFB. These data are the same as the theoretical forecast which could be extended to all hemodiafiltration methods in which solutions of any tonicity have to be infused, in order to correctly predict the Na balance.

The clinical value of correction of acidosis by acetate-free biofiltration in patients on regular dialysis treatment

Effects of metabolic acidosis were compared between bicarbonate dialysis (BCD) and acetate-free biofiltration (AFB). Three stable dialysis patients (1M, 2F, mean age 30 yrs) were selected for the study because their bicarbonate (BC) pre-dialysis plasma concentration were always under 16 mmol/l while they were on 33 mmol/l-BCD thrice weekly for 12 months. They were switched to a 6 months period of AFB. Pre- and post-dialysis BC plasma concentration, other blood chemical parameters and mass removal (total collection of used dialysate) of urea (U), creatinine (Cr), uric acid (UA), and phosphate (P) were measured during the last week of each period, including 3 dialysis sessions. Mean calorie and protein intake were 29.4 KCal/kg.d and 1.5 g/Kg.d (BCD period) and 38.2 Kcal/Kg.d and 1.5 g/Kg.d (AFB period) respectively. BC plasma concentration (Mean +/- SE, mmol/l) at the pre and post-dialysis in AFB were significantly higher than those in BCD (16.6 +/- 0.7 vs 20.8 +/- 0.6; p less than 0.001, 22.7 +/- 0.8 vs 25.8 +/- 0.8; P less than 0.02). Pre- and post-dialysis U plasma concentration (Mean +/- SE, mmol/l) in AFB were significantly lower than those in BCD (34.3 +/- 2.51 vs 20.8 +/- 0.59, 10.5 +/- 1.32 vs 7.5 +/- 0.92; P less than 0.001). Pre-dialysis P plasma concentration (Mean +/- SE, mmol/l) in AFB was significantly lower than that in BCD (1.85 +/- 0.09 vs 1.50 +/- 0.15; P less than 0.01). Cr, UA and P mass removal in BCD and AFB were not significantly different. However, U mass removal in AFB was significantly lower than that in BCD.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetate-Free Biofiltration: Hemodiafiltration with Base-Free Dialysate

Bicarbonate dialysis has several clinical advantages compared to conventional acetate hemodialysis. However, the use of bicarbonate in the dialysate requires complicated hardware with considerable maintenance and servicing. We have developed a new dialysis technique, a modification of hemodiafiltration, called acetate-free biofiltration (AFBF), with no base replacement agents in the dialysate and with the infusion of bicarbonate solution in postdilution fluid. This study consisted of two parts, an acute phase (8 dialysis patients) and a chronic phase (4 patients) lasting up to 12 months. In the first phase we evaluated the effects of different amounts of infused bicarbonate (from 751 to 1,002 mEq per session) on acid-base balance. The best correction of uremic acidosis was obtained with the infusion of 900-1,000 HCO3 mEq during a 3-hour AFBF. There was a significant (p less than 0.0001) positive correlation between infused and gained bicarbonate. In the chronic part, 880-910 HCO3 mEq was infused per session and there was an increase in mean pretreatment plasma bicarbonate from 18.1 +/- 2.2 upon starting to 22.8 +/- 0.4 mEq/l by the end of the 12-month period. A very low incidence of intradialytic hypotension and stable serum chemistries were achieved with this technique as compared with standard hemodialysis despite a reduction of 3 h in weekly treatment time. AFBF is an easy-to-use, safe alternative to bicarbonate dialysis thanks to the absence of pyrogen reactions and comparatively low-cost maintenance.

Acetate-free biofiltration: a viable alternative to bicarbonate dialysis.

Eight patients were studied during four sessions of acetate-free biofiltration (AFBF). AFBF is a new dialysis technique with no base replacement agents in the dialysate and with the addition in postdilution mode of bicarbonate (HCO3) solution directly into the extracorporeal blood circuit. In this study the effects on acid-base balance of different infusions of sodium bicarbonate (NaHCO3) ranging from 751 to 1,002 mEq per session was evaluated. There were significant positive correlations between the HCO3 infused and net HCO3 gained (r = 0.776, p less than 0.0001) and between HCO3 infused and plasma intratreatment HCO3 changes (n = 0.562, p less than 0.001). Stepwise multiple linear regression analysis demonstrated that HCO3 infused and plasma predialysis HCO3 values played the major role in HCO3 balance in AFBF. The best correction of metabolic acidosis was obtained with the infusion of 900-1,000 mEq of HCO3. The use of substitution fluid with 145 mEq/L of Na concentration avoids the risk of a positive intratreatment Na balance.