Acetate-free Biofiltration Research Articles

Model-based study of the effects of the hemodialysis technique on the compensatory response to hypovolemia

Hemodialysis technique (dialysate composition, filter, convection/diffusion ratio, etc.) can have an impact on the patient's tendency to acute hypotension. We have examined the hypothesis that the dialysis technique affects the hypotension risk by altering the cardiovascular compensatory response to hemodialysis-induced hypovolemia. Twelve hypotension-prone subjects were studied during six sessions of conventional bicarbonate dialysis (BD) and six sessions of acetate-free biofiltration (AFB). Blood volume (BV) control system was used in AFB to provide a BV change equivalent to the BV change observed in BD. The efficacy of reflex compensatory mechanisms was assessed by a model-based computer analysis of the BD and AFB sessions. BD sessions were complicated by hypotension more frequently than the AFB ones (34/66 BD vs. 18/66 AFB). Hypotension arose about 60 minutes earlier in BD (123 +/- 41 minutes in BD vs. 183 +/- 25 minutes in AFB, P < 0.01), and after a smaller BV reduction (hypotension BV 7.9%+/- 2.0% in BD vs. 10.9%+/- 2.6% in AFB, P < 0.05). Model-based computer analysis of the sessions without hypotension revealed differences in peripheral resistance adaptation (9%+/- 9% BD vs. 19%+/- 7% AFB, P < 0.05) as well as in the stroke volume reduction (19%+/- 8% BD vs. 10%+/- 8% AFB, P < 0.001). Model analysis of sessions with hypotension indicated that compensatory mechanisms were almost inoperative in BD, whereas a residual capacity to control peripheral resistance and cardiac contractility was present in AFB. Model simulations demonstrated that hypotension occurred later in AFB since the residual compensatory capacity in AFB was able to sustain the arterial pressure for larger BV reductions (8.3% BD vs. 11.2% AFB). The increased risk of acute hypotension in BD compared to AFB is caused by a therapy-induced inhibition of reflex compensatory response to hypovolemia.

Effect of acetate-free biofiltration and bicarbonate hemodialysis on neutrophil activation

Background: Activation of polymorphonuclear neutrophils (PMNs) and monocytes has been described during hemodialysis (HD), which results in the release of reactive oxygen species and cytokines. Acetate-free biofiltration (AFB) has been shown to cause less monocyte activation and cytokine release than bicarbonate HD (BHD). No data are available to date on the effect of AFB on PMN activation. Methods: We studied ex vivo superoxide anion release by PMNs isolated from nine patients treated in random order with AFB or BHD (three sessions each). Plasma interleukin-1β (IL-1β) levels and the nitric oxide (NO) synthetic pathway also were evaluated. A polyacrylonitrile (AN69; Hospal, Bologna, Italy) dialyzer was used for both treatments. Fourteen healthy volunteers were used as controls. Blood samples were drawn predialysis and 5 and 15 minutes after starting dialysis to obtain plasma and PMNs. Results: Neither ex vivo superoxide anion release nor blood PMN count was affected by AFB. Conversely, a peak in superoxide anion production associated with a decrease in PMN count was observed at 5 minutes during BHD. Results of superoxide anion production by control PMNs exposed in vitro to AFB or bicarbonate dialysis bath or Hank's balanced salt solution supplemented with bicarbonate or acetate indicated that BHD-induced PMN activation could be attributed to the amount of bicarbonate present in the dialysis bath. IL-1β plasma levels did not change during dialysis with AFB and were numerically higher at 5 and 15 minutes with respect to predialysis values during BHD. Uremic plasma obtained during either AFB or BHD induced greater NO synthesis by human umbilical vein endothelial cells than control plasma. Conclusion: AFB, unlike BHD, does not cause PMN and monocyte activation, which could have a positive impact on dialysis-associated cardiovascular disease of dialyzed patients. © 2002 by the National Kidney Foundation, Inc.

Online Hemodiafiltration Versus Acetate‐Free Biofiltration: A Prospective Crossover Study

Online hemodiafiltration (online HDF) and acetate-free biofiltration (AFB) are 2 innovative renal replacement therapies. Convincing evidence has shown that both techniques are superior to conventional hemodialysis in many aspects. The aim of the present investigation was to compare online HDF and AFB in 12 stable maintenance hemodialysis patients in a prospective, randomized crossover trial. Twelve stable dialysis patients, age 49.7 +/- 11.3 years and on dialysis for 83.5 +/- 76.7 months, were treated prospectively and randomly by either AFB, predilution HDF (pre-HDF), or postdilution HDF (post-HDF) for a total of 36 weeks using exclusively F60S high-flux dialyzers. Routine blood biochemical tests, bone metabolism parameters, and clearance for both small and larger molecular weight substances were measured at defined intervals. During the trial period inter- and intradialysis symptoms, e.g., hypotensive episodes and intradialysis arterial blood gas analyses, were recorded. Both online HDF and AFB were well accepted by the overwhelming majority of patients and also by the dialysis staff. Pretreatment sodium, total and ionized calcium, chloride, bicarbonate, and urea did not differ within or between the 3 treatment groups. Potassium increased slightly in HDF patients while phosphate and beta2-microglobulin (beta2-M) decreased in all groups. After dialysis, AFB patients exhibited a significantly higher bicarbonate concentration and lower potassium level when identical potassium concentrations in dialysate were used. Patients receiving AFB manifested less intradialysis partial pressure of oxygen drop and partial pressure of carbon dioxide rise than those on HDF treatments. HDF treatments could afford higher single-pool and double-pool Kt/V, higher effective urea and beta2M clearance, and lower total interdialysis symptom scores than the AFB treatment method. While bone metabolism parameters did not differ between the 3 dialysis modalities, some parameters such as deoxypyridinoline in HDF and osteocalcin, pyridinoline, and deoxypyridinoline in AFB deteriorated at the end of the crossover study. Aluminum concentration decreased progressively to about one-third of prestudy values at the end of the study with all 3 treatments. AFB was associated with a lower predialysis mean arterial pressure (MAP), a smaller drop in MAP during treatment, and similar hypotension episodes compared with the 2 HDF treatments. Albumin concentration showed a trend to decrease during the first 2 months of the trial period followed by a slight increase thereafter but still significantly lower than initial value at the end of crossover. Both online HDF and AFB share most of the features of optimal renal replacement therapy. Online HDF is superior to AFB in such aspects as increased delivered dialysis dose both for small and larger molecular weight toxins and less interdialysis symptoms. On the other hand, AFB is associated with a smaller effect on arterial blood gas values and improved intradialysis hemodynamic tolerance. Some dialysis-related symptoms and complications in the case of our AFB practice could be attributable, at least in part, to low dialysate calcium level.

Hémodialyse : actualités et perspectives

In all blood purification systems, as in the native kidneys, waste products are removed through a semi-permeable membrane. However, in contrast with the native kidneys, the solute transfer through the semi-permeable membrane is not necessarily a ‘convective transfer’ due to ultrafiltration. In conventional hemodialysis the transfer is mainly by diffusion, but the convective transfer can play an important role in particular hemodialysis procedures (hemofiltration,hemodiafiltration) requiring the infusion of a substitution fluid. In conventional hemodialysis, as in hemofiltration and hemodiafiltration, the qualitative and quantitative composition of dialysis and substitution fluids is usually similar to that of extracellular fluid. Newer dialysis procedures use dialysis and substitution fluids with a quantitatively non-physiologic composition. In acetate-free biofiltration, the dialysis fluid is base-free (without acetate or bicarbonate): the bicarbonate repletion of the patient is obtained by infusion of a solution containing sodium bicarbonate. In duo-cart biofiltration, the dialysis fluid contains only sodium chloride and bicarbonate: the ionic complement (potassium, calcium and magnesium chlorides) and glucose are infused in the extracorporeal blood line.

Preocupante incremento de la diabetes como causa de insuficiencia renal terminal: Evaluación del tratamiento sustitutivo

To study the incidence, prevalence, treatment modalities and prognosis of diabetic patients on renal replacement therapy. We studied all end-stage renal failure (ESRF) diabetic patients on renal replacement therapy in "Area Sanitaria 1" in Madrid from 1978 to 1998. Diabetes mellitus has become the leading cause of ESRF in our health area of Madrid, 30% of all causes of ESRF. Incidence of diabetics beginning RRT was 33.3 per million population (pmp) in 1998, while in 1993-94 diabetes was 15% and 21 pmp, respectively, table 1. The proportion of diabetics on RRT has increased from 7.4% 1986 to 12.7% 1998. The prevalence of diabetics on RRT in 1998 was 135 pmp, with an overall prevalence of 1054 pmp. At the mean time, the proportion between incident diabetics type 2/diabetics on RRT has increased from 15% in 1987-88, to 54% in 1993-94 and to 81% in 1997-98, consequently, mean age of diabetic patients at beginning RRT has increased from 47 years before 1988, 58 in 1989-90, 61 in 1993-94, 62 in 1995-96 and 63 in 1997-98 (Table I). We studied 182 diabetics admitted for renal replacement therapy, 106 males and 76 females, 105 were diabetics type 1 and 77 type 2. Their mean age at RRT beginning was 57.12 years (SD). Hemodialysis (HD) was the first modality of treatment for 128 (70%) diabetics and CAPD for 54. Seventy out of 128 patients on HD were dialyzed in the Hospital Unit, 40% on AFB (acetate free biofiltration) and 58 in two Satellite Units, that means a higher proportion of diabetics on CAPD and on HD in Hospital Unit. Diabetics allocated to CAPD were 5 years, as mean, younger than patients allocated to HD (p < 0.01) and the proportion of diabetes type 1 was higher in CAPD (72%) than in HD (51%), p 0.05. During the mean follow-up period (51.45 months) 79 patients changed their treatment modality and 45 of them received a kidney allogral. Relative risk of drop-out was higher in CAPD technique when compared to HD. Clinical complications were frequently observed: ocular (77%), cardiovascular (Myocardial infarction 1.7%), acute cerebrovascular disease (21%) and distal angiopathy (35%), 10% amputee. At December of 1998, 89 patients were dead. Cardiovascular and cerebrovascular diseases (29%) and Infections (27%) were the two most frequent causes of death. Unknown-origin deaths represent 19% of all deaths. The overall survival (Kaplan Meier) was 92%, 80%, 72%, 61% and 54% at 1, 2, 3, 4 and 5 years, respectively (57 patients completed last period). Survival was better on HD than on CAPD, but without statistical significance, although the significant difference in age and in proportion of diabetes type 2 between both groups. Data analysis estimated by Cox proportional hazards regression shows that younger age and ki,r transplantation had a positive independent effect on survival, whik clinical distal angiopathy had important negative effect on survival. Diabetes mellitus has become the leading case of ESRF in our health area of Madrid. Young age and kidney transplantation had a positive independent effect on survival, while clinical distal angiopathy had important negative effect.

The Effect of Hemodialysis and Acetate-Free Biofiltration on Anemia

The authors monitored, for a period of 12 months, anemia-, nutrition-, and free radical-related parameters and the rHuEPO dose required to maintain target hemoglobin (Hb) in 20 patients with chronic renal failure. Ten patients each were randomized for treatment by either acetate-free biofiltration (AFB) or low-flux hemodialysis (HD). At baseline, Hb levels were 102+/-2 (AFB) vs. 98+/-2 g/L (HD) (not significant difference, NS), the rHuEPO dose was 4050+/-976 vs. 5100+/-1538 lU/week (NS). Compared with baseline and with HD, lower rHuEPO doses were required during AFB at months 8, 9, 10 and 11, and 12 when they were 2100+/-510 (AFB) vs. 6000+/-1153 (HD), p=0.008. Prealbumin, transferrin and cholinesterase levels rose in the AFB group. Kt/V, albumin, transferrin saturation, aluminium, bicarbonate in serum, superoxide dismutase and glutathione peroxidase in erythrocytes, and malondialdehyde and antioxidant capacity in plasma did not differ between the AFB and HD groups. In terms of anemia control, AFB using an AN69 membrane was found to be more advantageous than low-flux HD, AFB improves some nutritional parameters. The compared methods do not differ in their effect on lipid peroxidation and the antioxidant system.

Homocysteine as a Cardiovascular Risk Factor

Hyperhomocysteinemia (HH), a known risk factor for vascular diseases, is a frequent condition in hemodialysis (HD) patients. HH induces an oxidant stress to the vascular endothelium, causing a failure of vasodilation and an impairment of the antithrombotic properties. Vitamins B₆, B₁₂ and folic acid are important cofactors for the enzymes in the catabolism of homocysteine (Hcy). Failure of Hcy catabolism forces the cell to export Hcy into the plasma. The kidney is an important metabolic site for removal (up to 70%) of plasma Hcy (P-Hcy). HD lowers the P-Hcy concentration by 29 and 41% with cellulosic and noncellulosic membranes, respectively, yet values return to normal in only a few patients. Clearly, we must decrease the dangerous high levels of Hcy in different ways. Vitamin Supplementation: Vitamins B₆, B₁₂ and folic acid decreased the basal level of Hcy by about 40%, starting from the sixth month. Membranes: Some membranes performed better than the others. Techniques: On the chronic basis, in our 1-year experience, paired filtration dialyis led to the best results, when compared to bicarbonate dialysis and acetate-free biofiltration. Finally, as in HD patients no one type of treatment can normalize the P-Hcy concentration, we should try other, different strategies such as absorption, the use of liposomes and new types of supplementation.

Short-term outcome of diabetic patients in renal replacement therapy.

Diabetic nephropathy or diabetes-related nephropathies represents one of the most relevant causes of renal failure in recent years. This complex pathological picture becomes particularly severe as time elapses and after starting renal replacement therapy (RRT). In an attempt to investigate the evolution of the major clinical features, a retrospective study was carried out on a cohort of 76 diabetic patients on RRT. Sixty-five have been treated by haemodialysis (HD) and 11 by peritoneal dialysis (CAPD), for at least 1 year. In these patients change in modality of treatment, metabolic control, cardiovascular, and ophthalmological complications, peripheral neuropathy, state of vascular access, and intradialytic complications were surveyed at initiation and after 1 year of treatment. A modified Karnofski's score was utilized, to evaluate the degree of rehabilitation. The comparison of prevalence was evaluated, using Student's t-test for paired samples. After 1 year, 11 patients on CAPD remained on the same type of treatment. Out of 65 patients on standard bicarbonate HD, 11 were moved to acetate free biofiltration, two to paired filtration dialysis and one to haemofiltration. A worsening in arrhythmias was recorded with an increased prevalence from 25.0 to 35.0% (n.s.), and one more patient (15 vs 16 and 19 vs 20 respectively) experienced ischaemic cardiomyopathy and cerebrovascular insufficiency. Hypertension showed a significant improvement (72 vs 42, P<0.01). Nausea and vomiting, hypotensive episodes, and muscular cramps were more frequently observed. A worsening in patient's welfare was also recorded but without statistical significance. This clinical evaluation even if retrospective and lasting 1 year, may suggest that RRT does not per se represent a cause of the development and progression of the major complications related to diabetic disease.

Dialysis kinetics of homocysteine and reactive oxygen species.

In patients with chronic renal failure who undergo hemodialysis (HD), the antioxidant system is inadequate to correct the imbalance between the generation and scavenging of reactive oxygen species. To clarify the role of six different membranes on oxidative stress, the authors measured plasma lipid peroxidation and erythrocyte (E) concentrations of several antioxidant enzymes in 30 HD patients: 20 on bicarbonate HD, 4 on paired filtration dialysis, 3 on acetate free biofiltration, and 3 on hemodiafiltration. Before, during, and after the first session of the week (at times 0, 30, 60, and 120 min, end, and 30 min after end of HD), several blood samples were drawn. Plasma (P) homocysteine (HCY), cysteine (CYS), malondialdehyde (MDA), E-glutathione (GSH), glucose-6-phosphodehydrogenase, glutathione reductase (GR), glutathione peroxidase (GP), catalase (CAT), and superoxide dismutase (SOD) were determined. All six membranes (Hemophan [HEMO]; cellulose diacetate [DIAC]; acrylonitrile-69 [AN69]; polymethylmethacrylate [PMMA]; cuprammonium rayon [CURAY]; polysulfone plus hemophan [PS + HEMO]) induced a significant decrease in plasma lipid peroxidation (p < 0.001) and an increase in E-GSH, GR, GR + flavinadenine dinucleotide, GP, and SOD (p < 0.001). Some membranes, however, showed some peculiar effects on reactive oxygen species: HEMO is better than DIAC, as far as P-MDA and P-HCY are concerned; PMMA induces higher changes in E-GR and P-CYS than does HEMO; and patients chronically using PMMA and PS + HEMO membranes show the lowest P-HCY levels both before and after dialytic sessions. Based on these changes, implications as to the effects on vascular disorders could be derived.

Effect of acetate, bicarbonate dialysis, and acetate-free biofiltration on nitric oxide synthesis: Implications for dialysis hypotension

The effect of acetate dialysis (AD), bicarbonate dialysis (BD), and acetate-free biofiltration (AFB) on nitric oxide (NO) synthesis and the implications for dialysis hypotension was studied. The finding that uremic plasma is a potent inducer of NO synthesis by endothelial cells in vitro suggested that the cardiovascular instability of dialysis patients might result from excessive NO formation. Cardiovascular instability is more frequent in patients undergoing AD than BD. To see whether these differences were attributable to NO, we studied the NO synthetic pathway ex vivo in patients undergoing different dialysis procedures. Five patients were treated, in a random order, with AD, BD, and AFB, a technique using a buffer-free dialysate and postdilution of a sterile bicarbonate solution. Each type of dialysis was used for 1 week, comprising three dialysis sessions. A polyacrylonitrile dialyzer was used for all three methods. Before and after the third dialysis, plasma was collected, added to [3H]L-arginine, and incubated with human umbilical vein endothelial cells (HUVECs) for 24 hours. NO synthesis was evaluated as [3H]L-citrulline formation. Plasma concentrations of interleukin-1beta (IL-1beta), a potent inducer of inducible NO synthase (iNOS) in endothelial cells, were also measured. Plasma collected from patients after AD stimulated endothelial NO synthesis more than plasma from the same patients before the dialysis session (pre-AD, 0.173+/- 0.028 nmol/10(5) cells v post-AD, 0.280+/-0.093 nmol/10(5) cells; P < 0.05). A slight, although not significant, increase was also observed when HUVECs were incubated with plasma drawn after BD (pre-BD, 0.151+/- 0.014 nmol/10(5) cells; post-BD, 0.230+/-0.055 nmol/10(5) cells). AFB did not aggravate the stimulatory effect of uremic plasma on endothelial NO synthesis (pre-AFB, 0.184+/-0.038 nmol/10(5) cells; post- AFB, 0.189+/-0.040 nmol/10(5) cells). Plasma IL-1beta was greater (P < 0.01) after AD than after BD and AFB (post-AD, 0.234+/-0.028 pg/mL; post-BD, 0.124+/-0.019 pg/mL; post-AFB, 0.120+/-0.013 pg/mL). With AD, there was a greater intradialytic decrease in systolic blood pressure than with BD or AFB. Weight and blood volume loss and sodium balance were similar in AD, BD, and AFB. These data were consistent with the possibility that NO and cytokines, released in excessive amounts during AD, may contribute to hemodynamic instability. (Am J Kidney Dis 1998 Jul;32(1):115-24)

Estimation of mass transfer through a hemodialyzer: theoretical approach and clinical applications.

The estimation of the solute mass transfer through a dialyzer is generally based on the solute dialysance, but the concept of dialysance has been precisely defined only in the case of a merely diffusive transfer. In actuality the mass transfer of a solute is also influenced by the ultrafiltration responsible for a convective transfer and, if the solute is an ionic substance, by the transmembrane gradient of electrical potential due to the Gibbs-Donnan effect. The aim of this paper is to generalize the concept of dialysance when the diffusive, convective, and electric components of the transfer are simultaneously active. There are at least 3 modes to generalize the concept of dialysance for it to be identical, when the amount of ultrafiltration and the Gibbs-Donnan effect are negligible, to the usual dialysance defined in the case of a merely diffusive transfer. The dialysance can be defined so that it can be equal to the clearance for a solute absent from the dialysate again, so that it still represents the rate at which the plasma concentration of a given solute is reaching its equilibrium value, or so that it represents the merely diffusive component (independent of the ultrafiltration rate) of the mass transfer. This generalized concept of dialysance can be useful to provide a real-time estimation of the effective dialysis dose actually delivered to the patient; to automatically optimize, by a biofeedback process, the sodium balance during a hemodialysis session; and to adapt dialysate concentrations for new hemodialysis techniques with convective transfer (acetate-free biofiltration).

Investigation of fluoride elimination during a dialysis session

We have conducted a study of the elimination kinetics of fluoride ions by a log linear regression analysis of plasma levels obtained during a bicarbonate hemodialysis session, with a dialyzer in polymercaprin for six patients with chronic renal failure. Using plasma fluoride levels of 35 patients studied for 20 months, we have validated these kinetics for hemodialysis with sodium bicarbonate, acetate-free biofiltration, hemodiafiltration with low flow rate and other dialyzers. Our results show that the decrease in plasma fluoride levels is statistically significant only after the first hour, and the fall reaches approximately 30% after a 4 h dialysis session. We propose that post-dialysis measurements of plasma fluoride are now not necessary if levels before dialysis are known.

Acetate-free biofiltration in two patients simultaneously

Acetate-free biofiltration in two patients simultaneously

Accidental Aluminum Intoxication in Patients Undergoing Acetate-Free Biofiltration

Eight patients undergoing acetate-free biofiltration (AFB) suffered aluminum intoxication. The source of this outbreak was parenteral exposition to high concentrations of aluminum in sodium bicarbonate solutions. The manufacturer of bicarbonate solutions used in AFB was substituted in May 1994 and the solutions were stored in glass containers. At the peak of intoxication (July 1994) serum aluminum determination revealed an average value of 147.3 ± 21 µg/l. Aluminum levels in bicarbonate solutions were 400 µg/l. Serum ferritin rose from 307.4 ± 161 to 735.6 ± 206 ng/ml, whereas MCV decreased significantly from 98.4 ± 9 to 90.1 ± 10 fl. No significant changes were found in hemoglobin, neither in plasma iron, nor in iron transferrin saturation. The doses of recombinant human erythropoietin showed a considerable increase. The replacement solutions were changed and a new solution, stored in plastic containers and with aluminum levels lower than 10 µg/l, was used. The biochemical parameters were normalized. This outbreak demonstrates the need for a stringent control of aluminum-containing replacement fluids.

Dialysis efficacy during acetate-free biofiltration

Dialysis efficacy during acetate-free biofiltration

Acetate-free biofiltration for acute renal failure

The characteristics of acetate free biofiltration (AFB) are now well documented in patients with chronic renal failure: hemodynamic tolerance, correction of acid-base imbalance, buffer free dialysate (without acetate) and absence of backfiltration. This hemodialysis technique can be beneficial to patients with acute renal failure (ARF). In our intensive care unit, we prospectively studied 29 patients with isolated ARF or ARF associated with failure of other organs. All eligible patients were randomly assigned to undergo dialysis with bicarbonate hemodialysis (BH) or with (AFB). All used the same high flux biocompatible dialysis membranes. Effectiveness and hemodynamic tolerance of hemodialysis sessions and evolution of patients were analyzed.Correction of metabolic disorders, although better in the AFB group was not statistically different from that in the BH group. Re-equilibration of acid-base balance was also similar, with or without mechanical ventilation. Heparin consumption was significantly higher in the AFB group, with no effect on haemorrhagic complications. Analysis of hypo- and hypertensive episodes, defined as arterial pressure (AP) variations 20% greater than initial pressure, showed no difference in terms of number or degree of AP variation. However, weight loss and the rate of ultrafiltration led to a higher hypotensive risk in the BH group (p < 0.05). Finally, the clinical course and prognosis was similar in both groups.In summary, AFB may be considered as effective a hemodialysis technique as BH in patients with ARF. Weight loss was better tolerated in the AFB group and can be a favorable factor considering the deleterious effect of overhydratation in patients admitted to an intensive care unit. This study invites a comparison of longer dialysis session of AFB therapy and continuous hemodiafiltration.

The influence of correction of acidosis on plasma level of branched-chain amino acids in chronic hemodialysis patients

Seven patients undergoing chronic hemodialysis three times a week and whose plasma bicarbonate concentration on predialysis was consistently under 18 mmol/l due to bicarbonate dialysis (BCD), were treated with BCD for 2 weeks, then switched to acetate-free biofiltration (AFB) for 8 weeks. In both periods, the same high flux dialyzer (AN69HF) was used. The treatment time, dialysate flow rate and blood flow rate were kept constant in each patient during both periods. Plasma bicarbonate concentration (HCO3-), serum urea nitrogen (SUN), serum creatinine (Cr) and plasma amino acids concentrations (AA) were measured before dialysis and KT/V was calculated on the 2nd days of the last week in both periods. HCO3- on AFB was significantly higher than that on BCD (16.4 +/- 0.9 vs 19.9 +/- 1.8 mmol/l; p < 0.05). SUN on AFB was significantly lower than that on BCD even though the dialysis schedule and dietary content were not changed (84.7 +/- 3.7 vs 76.6 +/- 3.8 mg/dl; p < 0.05). TP, Cr and KT/V were not significantly different. Plasma total amino acid concentration (TAA) and plasma essential amino acid concentration (EAA) were not significantly different in both periods. In contrast, plasma branched-chain amino acid concentrations (BCAA) on AFB were significantly higher than that on BCD (313.5 +/- 44.3 vs 390.3 +/- 50.7 mumol/l; p < 0.05). Plasma BCAA concentrations, valine (VAL), leucine (LEU) and isoleucine (ILE), were significantly higher on AFB than that on BCD, respectively (p < 0.05). These findings suggest that optimal correction of the metabolic acidosis in chronic hemodialysis patients by AFB leads to a significant increase in plasma BCAA concentration.

44. Improved dialysis efficacy during acetate free biofiltration

44. Improved dialysis efficacy during acetate free biofiltration

A prospective comparison of bicarbonate dialysis, hemodiafiltration, and acetate-free biofiltration in the elderly

Hemodiafiltration (HDF) and more recently acetate-free biofiltration (AFB) have shown good blood purification and cardiovascular stability in young and middle-aged hemodialysis patients. It is not clear if this is also valid for elderly patients. Twelve patients aged more than 70 years (mean age ± SD, 76 ± 4 years) on regular dialysis for at least 5 months were treated with bicarbonate dialysis (BD), HDF, or AFB in a randomized sequence and prospectively followed for 6 months (72 dialysis sessions/patient) for each procedure. The dialysis solution (containing bicarbonate), blood flow rate, and dialysate flow rate were the same with all the methods. During HDF and AFB solutions containing bicarbonate at a concentration of 27 to 30 mEq/L and 145 mEq/L, respectively, were infused postdilution at a rate of 66 ± 7 mL/min and 2.81 ± 0.12 L/hr, respectively. During the period of observation we evaluated the number of intradialytic hypotensions, the episodes of nausea, vomiting, headache (dialysis intolerance), body weight, the interdialysis weight gain, the duration of the dialysis session, the number of hospitalizations/patient, and the length of hospitalization/patient. At the end of each observation period we determined: Kt/V, protein catabolic rate, acid base balance, serum creatinine, serum calcium, serum phosphorus, alkaline phosphatases, and serum intact parathyroid hormone. After the switch from BD to either HDF or AFB, the results have shown a significant reduction of dialysis hypotension episodes (18% on BD, 14% on HDF, and 13% on AFB; BD v HDF, P = 0.001; BD v AFB, P = 0.0001; and HDF v AFB, P = NS) and of dialysis intolerance (3.3% on BD, 1.3% on HDF, and 1.1% on AFB; BD v HDF, P = 0.021; BD v AFB, P = 0.019; and HDF v AFB, P = NS). Kt/V improved significantly after the switch from BD to either HDF or AFB (1.17 ± 0.06 on BD, 1.32 ± 0.12 on HDF, and 1.32 ± 0.13 on AFB; BD v HDF, P = 0.021; BD v AFB, P = 0.003; HDF v AFB, P = NS). Protein catabolic rate also improved in HDF and AFB compared with BD (0.90 ± 0.12 on BD, 1.03 ± 0.15 on HDF, and 1.04 ± 0.14 on AFB; BD v HDF, P = 0.001; BD v AFB, P = 0.009; and HDF v AFB, P = NS). AFB showed a better correction of acidosis compared either with BD or HDF (serum bicarbonate, 20.3 ± 1.1 mEq/L on BD, 20.8 ± 2.2 mEqL on HDF, and 22.2 ± 2.4 mEq/L on AFB; BD v HDF, P = NS; BD v AFB, P = 0.01; and HDF v AFB, P = 0.030). The other parameters observed did not differ. In conclusion HDF and AFB show a better dialysis efficiency and a better hemodynamic tolerance compared with BD. This fact is associated with an improvement in protein intake as assessed by kinetic criteria. Acetate-free biofiltration has the further advantage of a better control of the acid-base balance compared with BD and HDF. HDF and AFB are useful dialytic options to traditional BD hemodialysis even in patients older than 70 years.

Preventing haemodynamic instability in patients at risk for intra-dialytic hypotension.

Although as yet no major breakthroughs have occurred to improve long-term survival of haemodialysis patients with impaired cardiovascular function, it is possible to reduce morbidity by intra-dialytic hypotension in these patients by the use of relatively simple manoeuvres. In our experience, this can be achieved using the following approach (Table 1). First, the decline in plasma volume can be reduced by adequate estimation of the optimal dry weight by objective methods, such as echography of the inferior caval vein or bioimpedance measurements. Furthermore, the ultrafiltration rate during haemodialysis should be moderate and should be limited to a maximum value, which has to be defined empirically for each individual patient. Especially in patients with excess inter-dialytic weight gain, isolated ultrafiltration should be used when the required amount of fluid cannot be removed during haemodialysis. The use of low-sodium dialysate should be avoided. Probably it is best to use a physiological sodium concentration of the dialysate because a greater sodium concentration may result in increased thirst and intra-dialytic weight gain. Sodium profiling should be based on further studies concerning plasma volume changes during haemodialysis in different patient groups. Because of the deleterious impact of acetate on vascular reactivity, it should never be used in patients prone to hypotensive periods. Vascular reactivity can also be impaired by the use of vasoactive medication prior to haemodialysis treatment. Therefore, in patients prone to hypotensive periods, vasoactive medication should be withheld the morning before haemodialysis, if possible. Also, one should be very cautious with the use of low-calcium dialysate in patients with frequent hypotensive periods, and ideally it should be avoided. If the use of these manoeuvres fails to control intra-dialytic hypotension, one should consider the use of cold dialysate. Switching to haemofiltration or to continuous treatment modes such as CAPD are other options. Future studies should address haemodynamics during other treatment modes, such as haemodiafiltration or acetate-free biofiltration.