Helmut Mann

A Critical Review of Sodium Profiling for Hemodialysis

In sodium profiling, the sodium concentration in the dialysis fluid, instead of being constant, follows a time‐dependent profile over the course of a hemodialysis session. The main aim of this manipulation is to avoid osmotic disequilibrium by keeping plasma osmolality in the physiological range. Further advantages of sodium profiling are a reduction in the incidence of muscle cramps, improved sodium removal, and improved vascular stability. Many different profiles have been used by various investigators. However, if sodium profiling is not appropriately conducted, sodium accumulation with resulting augmented thirst, increase of interdialytic weight gain, and hypertension may result. Sodium accumulation may, in fact, explain the reduced intradialytic morbidity reported in some short‐term sodium profiling studies. Randomized, double‐blind studies meeting strict statistical criteria and providing a careful control to maintain equivalent sodium balances between the compared treatments are difficult to perform and have not yet been published. However, because sodium profiling has potential benefits, provided that sodium balance is carefully controlled, it should nevertheless be regarded as a tool that experienced nephrologists can use for the treatment of patients who experience intolerable side effects during standard dialysis.

Pathological excretion patterns of urinary proteins in miners highly exposed to dinitrotoluene.

A cohort of 161 underground miners who had been highly exposed to dinitrotoluene (DNT) in the copper-mining industry of the former German Democratic Republic was reinvestigated for signs of subclinical renal damage. The study included a screening of urinary proteins excreted by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and quantitations of the specific urinary proteins &agr;1-microglobulin and glutathione-S-transferase &agr; (GST &agr;) as biomarkers for damage of the proximal tubule and glutathione-S-transferase &pgr; (GST &pgr;) for damage of the distal tubule. The exposures were categorized semiquantitatively (low, medium, high, and very high), according to the type and duration of professional contact with DNT. A straight dose-dependence of pathological protein excretion patterns with the semiquantitative ranking of DNT exposure was seen. Most of the previously reported cancer cases of the urinary tract, especially those in the higher exposed groups, were confined to pathological urinary protein excretion patterns. The damage from DNT was directed toward the tubular system. In many cases, the appearance of Tamm-Horsfall protein, a 105-kD protein marker, was noted. Data on the biomarkers &agr;1-microglobulin, GST &agr;, and GST &pgr; consistently demonstrated a dose-dependent increase in tubular damage, which confirmed the results of screening by SDS-PAGE and clearly indicated a nephrotoxic effect of DNT under the given conditions of exposure. Within the cluster of cancer patients observed among the DNT-exposed workers, only in exceptional cases were normal biomarker excretions found.

Plasma endothelin-1 in hemodialysis treatment - the influence of hypertension.

In patients on chronic hemodialysis hypotensive episodes are frequently encountered during the course of treatment and the prevalence of atherosclerosis is increased. Endothelin-1 (ET-1), an endothelium-derived peptide with vasoconstrictive and mitogenic effects on smooth muscles, is involved in vascular tone regulation and in the pathogenesis of atherosclerosis. The aim of the present study was to investigate plasma ET-1 during hemodialysis treatment and to explore the probable influence of pre-existing hypertension. Forty-seven hemodialysis patients (21 females, mean age 62 ± 12 years) were evaluated and hypertensive patients (n = 33) were compared to normotensive patients (n = 14). Relative blood volume changes (hemoglobinometry) and blood pressure were measured. Samples were taken before, every hour during and after hemodialysis. Plasma ET-1 was measured by enzyme-linked immunosorbent assay and results were corrected according to hemoconcentration. Hemodialysis with an ultrafiltration rate of 2224 ± 933 mL was performed. Total blood volume at the end of hemodialysis was 89.4 ± 8.2% of the pretreatment volume. The fall in blood pressure (137/74 ± 22/11 mmHg vs 127/73 ± 30/14 mmHg) correlated with the decrease in blood volume (mean blood pressure: r = 0.33). Plasma ET-1 increased from 1.29 ± 0.47 pg/mL before to 1.46 ± 0.56 pg/mL (reference range 0.3-0.9) at the end of hemodialysis (P < 0.05). This rise was more pronounced in patients with hypertension than in normotensive individuals (P < 0.05). The change in blood volume (r = 0.41) and blood pressure (mean blood pressure: r = 0.34) correlated with plasma ET-1 at the end of hemodialysis (P < 0.05). Plasma ET-1 was enhanced in hemodialysis patients compared to normal subjects. During the hemodialysis session an increase in ET-1 was encountered, which was more pronounced in hypertensive than in normotensive patients and paralleled the hemodynamic changes. Apart from pre-existing hypertension, further factors potentially influencing ET-1 include local endothelial injury (arteriovenous fistula) and generalized bioincompatibility reactions (e.g. foreign surface contact) occurring during hemodialysis.

Response of Vasoactive Substances to Intermittent Ultrafiltration in Normotensive Hemodialysis Patients

The changes in blood volume (BV), atrial natriuretic peptide (ANP), plasma renin activity (PRA), aldosterone (Aldo), norepinephrine (NE), epinephrine (Epi), parathyroid hormone (PTH), arginine vasopressin (AVP) and the cyclic nucleotides cAMP and cGMP were measured during a fluctuating BV cycle in 15 patients with end-stage renal failure maintained on chronic hemodialysis (HD). HD consisted of 4 periods of about 60 min each. The first half of each HD period consisted of ultrafiltration (UF) greater than 1,000 ml/h, and the second half consisted of no UF. Changes in relative BV were measured using continuous hemoglobinometry. Total BV at the end of treatment was 74.3 +/- 6.9% of the pretreatment volume. A significant positive correlation between BV and the levels of ANP, PTH, Epi and cGMP and an inverse correlation between BV and PRA, Aldo, AVP and NE were demonstrated. While mean values of NE and AVP levels were directly related to actual changes in BV, individual values did not homogeneously reflect this relationship. The cyclic nucleotides cGMP and cAMP did not follow immediate BV changes, but showed a significant decrease correlated with diminished BV. Based on a pre-postdialysis analysis, significant changes in PRA and Aldo were missing. It seems possible that vascular stability in dialysis patients may be maintained by the response of NE and AVP, and not by the renin-aldosterone system. The changes in ANP and cGMP values correlated most significantly (r = 0.38 and r = 0.51, p < 0.005) with the changes in BV, but no single variable could explain the blood pressure regulation during HD with intermittent rapid UF.

A Model of Solute Transport Through the Dialyzer Membrane in Hemodiafiltration

Hemodialysis (HD) using highly permeable membranes does not provide sufficient clearance for removal of high molecular uremic toxins such as b2-microglobulin (b2M). With increasing molecular weight the diffusive transport, which in hemodialysis is nearly identical with total transport, becomes ineffective. Hemodiafiltration (HDF) including convective transport can provide sufficient clearance over the total range of molecular weight of uremic toxins. In this article a mathematical model is outlined which calculates dialyzer clearance from dialyzer geometry and membrane permeability in hemodiafiltration for hollow fiber dialyzers. Additionally, transport of endotoxin fragments from dialysate to blood by backfiltration and backdiffusion is considered. The model is based on former work of the authors (1) and on the investigations of A. Wüpper (2, 3) who has evaluated a similar model. Clearance in hemodiafiltration depends on HDF mode: predilution, postdilution HDF parameters: blood flow, dialysate flow, filtration rate, hematocrit Dialyzer geometry: membrane area, length and inner diameter of the capillaries Membrane properties: permeability, sieving coefficient Changes in membrane permeability by a protein layer on the inner surface of the hollow fiber and absorption in the membrane are not included in the model.

Molecular weight distribution in the ultrafiltrates of different filters used for continuous arteriovenous hemofiltration

SummaryThe present study shows that liquid chromatography, especially as high performance size exclusion chromatography, is a useful tool to characterize newly developed highly permeable membranes, which are used for continuous arteriovenous hemofiltration (CAVH) of patients with renal failure. The molecular weight distribution in the ultrafiltrates of three hemofilters are compared using three different chromatographic systems. Especially in the region of the so-called “higher” molecular weight uremic toxins (MW above 2000 Dalton), the elution patterns of the filtrates show typical membrane-dependent differences. As we have shown earlier, the elimination of these higher molecular weight fractions might be of clinical relevance, as they contain inhibitors of DNA-synthesis in vitro.

Apport protéique journalier 1, 2 - est-ce la panacée ?

Resume La malnutrition proteique est un facteur important pour la survie des patients hemodialyses. Pour cela les professionnels de la nutrition recommandent un apport proteique journalier standard de 1,1 a 1,2 g/ (kg × jour) [9]. Mais ceci ne tient pas compte de l’âge ni du sexe des patients. Les analyses du taux du catabolisme proteique ( protein catabolic rate PCR) a l’aide de la cinetique de l’uree presentees ici montrent cependant une correlation avec l’âge et avec le sexe des patients, des que l’on se refere au PCR par rapport au poids absolu. Si le PCR se refere au poids maigre les differences liees au sexe disparaissent. Nous preconisons donc de calculer les besoins proteiques en tenant compte de la masse maigre et non pas par rapport au poids corporel brut et de tenir egalement compte de l’âge des patients dans les recommandations alimentaires.

Sekundärer Hyperparathyreoidismus und Sonographie der Epithelkörperchen bei Dialysepatienten

Der sekundare Hyperparathyreoidismus stellt nach wie vor eine der Hauptkomplikationen der chronischen Niereninsuffizienz bei Langzeitdialyse dar. Im Skelett uberwiegt die osteoklastare Resorption den osteoblastaren Neuanbau; es kommt zur Endostfibrose und zum Auftreten von minderwertigem Faserknochen entsprechend einer Ostitis fibrosa. Daneben konnen aber auch Veranderungen der Knochenmasse wie eine Osteosklerose oder Osteopenie auftreten. Die Patienten klagen uber vermehrte Knochenschmerzen.