Evaluation of a new online hemodiafiltration mode with automated pressure control of convection.

BACKGROUND: Postdilution hemodiafiltration (HDF) still remains the gold standard for solute removal, but with high hemoglobin levels transmembrane pressure (TMP) may reach high levels, reducing filter performance. We compared three online postdilution HDF treatments without TMP alarms for convective volume and plasma changes following treatment. METHODS: Twelve patients were enrolled in a trial with three online postdilution HDF treatments. In the volume-controlled mode (VOLc), we set the exchanged volume to obtain a filtration fraction close to 25% without TMP alarms. In the pressure-controlled mode (TMPc), we set the TMP at 100 mm Hg. In the ULTRAc mode (TMP scan combined with TMPc), the dialysis machine automatically selects the TMP with a scan. All treatments were performed with an AK200 ULTRA-S system. RESULTS: Even with hemoglobin levels >12 g/dl, we found a 57% rise in ultrafiltration rate in TMPc versus VOLc and a 92% rise in ULTRAc versus VOLc. Phosphates and myoglobin levels were significantly affected by treatment type. CONCLUSIONS: ULTRAc may be a useful tool to achieve an excellent purification performance without the constraints associated with the risk of hemoconcentration.

A new method to evaluate patient characteristic response to ultrafiltration during hemodialysis.

BACKGROUND: Several factors are involved in the pathogenesis of dialysis discomfort interfering with optimal fluid removal and reducing the efficacy of the treatment; the most important one is a decrease in blood volume caused by an imbalance between ultrafiltration (UF) and plasmarefilling (PR) rates. OBJECTIVES: This study is aimed at devising a method to tailor the dialysis therapy to each individual patient, by analyzing the relationship between PR and UF during the sessions in stable patients and widening the knowledge of fluid exchanges during the treatment. METHODS: Thirty stable patients undergoing maintenance hemodialysis were enrolled. Three dialysis sessions were monitored for each patient; systemic pressure, blood composition, blood volume % variation, weight loss and conductivity were recorded repeatedly. A Plasma Refilling Index (PRI), defined and calculated by means of parameters measured throughout the dialysis, was introduced as a novel instrument to study plasma refilling phenomena. Results. The PRI provides understanding of patient response (in terms of plasma refilling) to the set UF. In the monitored sessions, the PRI trend is found to be characteristic of each patient; a PRI course that is at variance with the characteristic trend is a signal of inadequate or unusual dialysis scheduling. Moreover, statistical analysis highlights two different PRI trends during the first hour and during the rest of the treatment, suggesting the presence of different treatment phases. CONCLUSION: The main advantage of the PRI index is that it is non-invasive peculiar to each patient and easy to compute in a dialysis routine based on online data recorded by the monitor. A deviation from the characteristic trend may be a warning for the clinician. The analysis of the PRI trend also suggests how to modulate UF as a function of interstitial to intravascular fluid removal balance during dialysis.

Microcirculation as a novel marker of membrane biocompatibility.

BACKGROUND: It is possible to consider microcirculation as a kind of OwitnessO of the complex biological reactions triggered by the dialytic treatment. The reactivity of microcirculation to the dialytic stress may represent a measure of the overall biocompatibility of the membrane. In this study we tested the hypothesis that different synthetic membranes may have different biological effects, particularly related to microcirculation. SUBJECTS AND METHODS: In this crossover study, we observed 16 chronically hemodialyzed patients. All patients were treated with the EVAL membrane; we recorded the TcPO2 during the second treatment of the week. All patients were then switched to the hf-PS membrane. During the study observation we did not change the dialytic prescription or the pharmacologic treatment. RESULTS: From the beginning of the session until 90O, the behavior of TcPO2 is similar for both the membranes. From 120O to the end of the treatment in sessions with the EVAL membrane, the TcPO2 values come back to the starting level, whereas in the treatments with hf-PS the TcPO2, the values remain at a lower level; there was a significant difference between EVAL and hf-PS in the values recorded. Arterial blood gas values of paO2 and paCO2 are quite similar in the treatments with both the membranes, without any significant difference. CONCLUSIONS: The analysis of microcirculation by means of TcPO2 measurement is a useful tool to obtain a OclinicalO measure of biocompatibility of the dialytic treatment and different membranes may have different impacts on TcPO2.

[Guidelines on water and solutions for dialysis. Italian Society of Nephrology]. / Linee Guida su acque e soluzioni per dialisi.

The National Society of Nephrology has promoted the development of specific Italian Guidelines for dialysis fluids. Two previous national inquiries showed a wide variety in the type and frequency of both microbiological and chemical controls concerning dialysis water, reinforcing the need for specific standards and recommendations. An optimal water treatment system should include tap water pre-treatment and a double reverse osmosis process. Every component of the system, including the delivery of the treated water to the dialysis machines, should prevent microbiological contamination of the fluid. Regular chemical and microbiological tests and regular disinfection of the system are necessary. 1. Chemical quality (Table: see text). Treated tap water used to prepare dialysis fluid should be within European Pharmacopoeia limits at the water treatment system inlet and at the reverse osmosis outlet. In addition dialysate, concentrate and infusion fluids must comply with specific Pharmacopoeia limits. The physician in charge of the dialysis unit is advised to institute a multidisciplinary team to evaluate the requirement for added chemical controls in the presence of local hazards. 2. Microbiological quality (Table: see text). High microbiological purity of dialysis fluid--regularly verified--is a fundamental prerequisite for dialysis quality and every dialysis unit should aim as a matter of course to obtain "ultra-pure" dialysate (microbial count <0.1 UFC/mL, endotoxins <0.03 U/mL). On-line dialysate ultrafiltration and regular disinfection of dialysis machines greatly enhance microbiological purity. On-line dialysate reinfusion requires specific devices used according to corresponding instructions and to more frequent microbiological tests. Dialysis fluids for home dialysis should comply with the same chemical and bacteriological quality. The appendix reports the water treatment system's technical characteristics, sampling and analytical methods, monitoring time-tables, as well as the origin and effects of the main toxic substances. Suggestions and questions concerning these guidelines are welcome to nefrologia@sin-italy.org.

Hemofiltration in diabetic uremic patients.

The increasing number of Diabetic Uremic Patients (DUP) starting the substitutive treatment (ST) constitutes a difficult and often disappointing problem in terms of efforts, clinical results and side-effects. While treatment of these patients by C.A.P.D. is well documented, the adoption of Hemofiltration (HF), has been, up to now scarcely considered. In order to define the potentialities of a HF policy in the treatment of these patients, data from 6 DUP treated with postdilutional HF for a 10.6 months/patient period were collected on a multi-center basis and retrospectively examined. Good results were achieved in terms of vascular stability, control of arterial hypertension and of retinopathy, clinical complications and hospitalization rate. Although C.A.P.D. may represent a first choice treatment for DUP with residual function, satisfactory glicemic control, difficult blood access and a motivation to full autonomization, HF may constitute a logical alternative when C.A.P.D. should be unmanageable (visus impairment, history of repeated peritonitis and dismetabolism, considerable weight gain): an integration of HF and C.A.P.D. can assure PDU with a continuative treatment.

Is the dialysate fluid source of complement activating factors?

To distinguish between membrane-induced and dialysate-induced mechanism of complement activation attending hemodialysis (HD), the C3a plasma level and blood neutrophil count profiles have been determined during procedures performed with noncellulosic membranes, as PAN and PMMA (with minimal complement-activating potential) and, by comparison, with new cuprophane (that displays the greatest complement-activating potential). Furthermore, PAN and PMMA membranes have been used in 2 other blood purification methods: high efficiency hemofiltration (HEHF), in which there is no dialysate on the other side of the membrane, and hemofiltration without substitution fluid and with reinfusion of dialysis-regenerated hemofiltrate (HWSF), in which the dialysate is separated from the blood circuit by the hemofiltrate circuit. In addition, sequential dialysis-ultrafiltration (UFD) experiments with PAN membranes have been performed, where dialysate was present only in the second part of the procedure. In all the HD and UFD procedures LAL test assays were performed on dialysate at the same times as C3a and neutrophil determinations. Our findings seem to suggest that the dialysate can be a source of complement activating factors; complement activation detectable by C3a plasma levels can ensue when LAL test-positive material is present in the dialysate.

Haemofiltration without substitution fluid.

Haemofiltration at its best is able to give excellent clearances of solutes in a wide molecular weight range, but the need of large amounts of reliable substitution fluid makes this technique too expensive for more widespread application. In order to give an 'adequate' treatment by a safe, well tolerated, effective and comparatively cheaper method, haemofiltration without substitution fluid (HWSF) has been carried out. This method, consisting of the regeneration of appropriate amounts of pure convected plasma water by highly permeable, high surface area dialysis membranes, has been utilised for several months in four patients, with encouraging clinical results.

High-flux acetate haemodialysis: a single-centre experience.

One hundred haemodialysed patients have been treated for 4 h thrice weekly by acetate haemodialysis with high-flux dialysers (HAHD) 1.4-1.8 m2 and automated ultrafiltration control for 18.9 +/- 8.3 months. The aim of the study was to evaluate the efficacy of treatment as regards urea and beta 2-microglobulin removal, cardiovascular stability, acid-base balance and plasma Il-1 variations. Moreover medium-term observation of both lipid profile and basal beta 2-microglobulin concentrations were performed. With our current adequacy criteria (urea clearance greater than or equal to 120 l/week; KT/V greater than or equal to 1.2; beta 2-microglobulin removal greater than or equal to 150 mg/treatment), the occurrence of hypotension was 6% during 24,500 treatments. Cardiovascular stability was preserved by the increase of total peripheral resistances in response to cardiac output decrease. No disturbances of acid-base parameters were observed in spite of plasma acetate concentrations greater than 6 mmol/l. No variations of plasma Il-1 occurred during the session or 2 h later.

Erythrocyte ferritin in patients on chronic hemodialysis treatment.

Serum ferritin (SF) and erythrocyte ferritin (EF) were evaluated in 35 patients on chronic hemodialysis treatment (CHD), in 45 healthy subjects and in 22 nonnephropathic females with iron deficiency anemia. Twenty-five CHD patients with basal SF less than 500 micrograms/l were treated orally with 200 mg of Fe2+ for 2 months and the positive (hemoglobin increase greater than 1 g/dl) or negative response to the therapy was correlated to the basal levels of SF and EF. Three groups of CHD patients could be defined on the basis of their basal SF levels (hypo-, normo- or hyperferritinemic). Nine patients with increased SF levels had also EF levels significantly higher than the other CHD patients and controls since they were probably iron-overloaded. In the other 2 groups of CHD patients, EF levels were significantly higher than in controls for each level of SF probably because of the reduced utilization of iron by uremic bone marrow. Among the 25 treated CHD patients, only 5 responded to the therapy: 3 were hypoferritinemic while the other 2 responders had basal SF within the normal range. Four hypoferritinemic patients did not respond to the therapy. Four out of five responders had the lowest EF levels among CHD patients. EF measurement could be an important and useful test in detecting the presence of an iron deficiency erythropoiesis in CHD patients.