Direct Dialysis Quantification: Investigation of the Impact of Dialysate Preservation Techniques on Solute Assays

<i>Aims:</i> Urease-producing microorganisms may lower urea nitrogen (UN) during dialysate-side dosing. We investigated the impact of 3 proven preservatives (acetic acid, ceftazidime, thimerosal) on UN concentration, and the concentrations of creatinine (CR) and β₂-microglobulin (β₂M). <i>Methods:</i> The UN, CR and β₂M concentrations were assayed in 3 separate aliquots from 20 spent dialysate samples (ceftazidime, 125 mg/l, or 1% thimerosal, 1 ml/l, vs. control). The β₂M concentration was assayed in 10 further spent dialysate collections (concentrated glacial acetic acid, 5 ml/l, vs. control). Solute concentrations were compared with the concordance correlation coefficient (r_c). <i>Results:</i> Ceftazidime and thimerosal had little effect on the concentrations of UN and CR (r_c >0.97). For the β₂M concentration, agreement remained good (r_c >0.96) for ceftazidime and thimerosal (although the former tended to lower concentrations) but acetic acid was less optimal (r_c = 0.893). <i>Conclusions:</i> Ceftazidime and thimerosal may be used as dialysate preservatives without affecting the UN or CR concentrations. Thimerosal is to be preferred when studying β₂M. Acetic acid produces unacceptable inaccuracy when measuring β₂M.

Estimate the insulin absorption in diabetic patients on peritoneal dialysis

Good control of blood glucose obtains both with subcutaneus and with intraperitoneal insulin administration. Intraperitoneally administered insulin is absorbed more rapidly and evenly than subcutaneously administered insulin. It passes directly into the portal vein system. But insulin requirement in peritoneal insulin administration is higher then in subcutaneous. Factors affecting this insulin absorption are unclear, and our aim was to find the relationship of insulin absorption with the parameters, which theoretically might be play role in insulin absorption process. 10 diabetic patients on peritoneal dialysis were studied. Transport status was determined by a standard 4-hour peritoneal equilibration test (PET). Dialysate insulin was analyzed using the enzyme-linked immunosorbent assay (ELISA). As it was expected, intraperitoneal insulin absorption is related with membrane transport status, glicemia, infusion volume of dialysate and insulin dose. According to our results obese and dislipidemia are not important factors in insulin absorption process.

[Determination of the cations concentrations in the dialysis fluid by an atom absorption spectrometer]

The atom absorption spectrometer is introduced to determine the cation concentrations such as potassium, sodium, calcium and magnesium in the dialysis fluid. They are accurately determined by proper preparation and correct dilution ratio under the optimized measuring conditions. Compared with the current arbitrate methods (EDTA titration determination of calcium and magnesium), it supplements the methods of international and industrial standards for determination of cations.

3,4-DGE in peritoneal dialysis fluids cannot be found in plasma after infusion into the peritoneal cavity

OBJECTIVE

Glucose degradation products (GDPs) are important in the outcome of peritoneal dialysis (PD) treatment. 3,4-dideoxyglucosone-3-ene (3,4-DGE) is the most cytotoxic GDP found in conventionally manufactured fluids and may, in addition, be recruited from 3-deoxyglucosone (3-DG). It is not known what happens with those GDPs in patients during PD. The aim of this study was to investigate if the 3,4-DGE and 3-DG in PD fluids can be found in plasma during treatment.

DESIGN

PD patients were dialyzed with a conventional PD fluid containing 43 micromol/L 3,4-DGE and 281 micromol/L 3-DG. Parallel experiments were performed in rats as well as in vitro with human plasma. The rats were dialyzed with a PD fluid containing 100 micromol/L 3,4-DGE and 200 micromol/L 3-DG.

RESULTS

The concentration of 3,4-DGE in the peritoneum decreased at a much higher rate than 3-DG during the dwell. 3,4-DGE was not, however, detected in the plasma of patients or rats during dialysis. The concentration of 3-DG in plasma peaked shortly after infusion of the fluid to the peritoneal cavity. The concentration of 3,4-DGE during experimental incubation in plasma decreased rapidly, while the concentration of 3-DG decreased only 10% as rapidly or less.

CONCLUSION

3,4-DGE could not be detected in plasma from either PD patients or rats during dialysis. This is presumably due to its high reactivity. 3-DG may, on the other hand, pass through the membrane and be detected in the blood.

Suppression of ethanol-reinforced behavior by naltrexone is associated with attenuation of the ethanol-induced increase in dialysate dopamine levels in the nucleus accumbens

The opiate antagonist naltrexone suppresses ethanol-reinforced behavior in animals and decreases ethanol intake in humans. However, the mechanisms underlying these actions are not well understood. Experiments were designed to test the hypothesis that naltrexone attenuates the rewarding properties of ethanol by interfering with ethanol-induced stimulation of dopamine activity in the nucleus accumbens (NAcc). Simultaneous measures of the effects of naltrexone on dialysate dopamine levels in the NAcc and on operant responding for oral ethanol were used. Male Wistar rats were trained to self-administer ethanol (10-15%, w/v) in 0.2% (w/v) saccharin during daily 30 min sessions and were surgically prepared for intracranial microdialysis. Experiments began after reliable self-administration was established. Rats were injected with naltrexone (0.25 mg/kg, s.c.) or saline and 10 min later were placed inside the operant chamber for a 20 min waiting period with no ethanol available, followed by 30 min of access to ethanol. A transient rise in dialysate dopamine levels was observed during the waiting period, and this effect was not altered by naltrexone. Ethanol self-administration reliably increased dopamine levels in controls. Naltrexone significantly suppressed ethanol self-administration and prevented ethanol-induced increases in dialysate dopamine levels. Subsequent dose-effect analyses established that the latter effect was not merely a function of reduced ethanol intake but that naltrexone attenuated the efficacy of ethanol to elevate dialysate dopamine levels. These results suggest that suppression of ethanol self-administration by opiate antagonists is the result of interference with dopamine-dependent aspects of ethanol reinforcement, although possible additional effects via nondopaminergic mechanisms cannot be eliminated as a factor in opiate antagonist-induced reduction of ethanol intake.

Same therapy, same calcium mobilization? Exploring calcium exchange across body compartments using a patient-specific predictive model

BACKGROUND

Comprehensive, patient-specific models are essential to study calcium deposition and mobilization during dialysis. We aim to develop tools to support clinical prescriptions with a more accurate approach for the prediction of calcium mobilization while also considering major electrolytes and catabolites.

METHODS

We modified a multi-solute model predicting patient-specific dialysis response by incorporating a calcium buffer to represent bone exchanges. Data from four centers, involving 127 patients with six sessions each, were utilized. For each patient, three sessions were allocated for model training (ID123), while the remaining sessions were for validation (PRED456). The normalized root mean square error (nRMSE%) was used to evaluate both descriptive and predictive accuracy. Correlations between initial data and calcium exchanges were also assessed.

RESULTS

The overall nRMSE% for ID123 was 3.92%. For PRED456, it was 3.46% (ranging from a minimum of 1.17% for [Na+] to a maximum of 6.62% for [urea]). The median nRMSE% for plasma calcium varied between 1.13 and 8.32 for SHD sessions, depending on whether Ca_dialysis fluid (Cad) was ≥ or <1.50 mmol/L, respectively. For HDF sessions, the range was between 2.90 and 5.89. A significant and moderate correlation was found between overall calcium removal and the buffer balance. The most robust correlation observed was between the amount of calcium administered via post-dilution fluid and the overall calcium removal in the dialysis filter.

CONCLUSIONS

Identical therapy settings do not uniformly affect calcium mobilization, and our approach offers insight into calcium distribution across body compartments. This understanding will enhance clinical prescription practices.

HPLC study of uremic fluids related to optical dialysis adequacy monitoring

PURPOSE

The aim of this study was to investigate uremia-related high-performance liquid chromatography (HPLC) ultraviolet (UV) absorbance profiles of serum and spent dialysate and to study the removal of uremic retention solutes in connection with optical dialysis adequacy monitoring.

METHODS

10 uremic patients were investigated using online spectrophotometry at a wavelength of 280 nm over the course of 30 hemodialysis treatments. The dialysate and blood samples were taken and analyzed simultaneously using standard biochemical methods and reversed-phase HPLC. Filters with cutoff at 3 kDa and 70 kDa were used for the pre-treatment of the serum. The chromatographic peaks were detected by a UV detector at wavelengths of 254 and 280 nm.

RESULTS

This study indicated that the main solute responsible for UV absorbance in the spent dialysate is a low-molecular-weight, water-soluble, non-protein-bound compound uric acid (UA). Three additional uremic retention solutes - creatinine (CR), indoxyl sulphate (IS) and hippuric acid (HA) - were identified from the HPLC profiles. The number of detected HPLC peaks was not significantly different for a serum filtered through the 3 kDa or 70 kDa cutoff filters, and was lower for the spent dialysate, indicating that the molecular weight (MW) of the main UV chromophores in the uremic fluids did not exceed 3 kDa. The reduction ratio (RR) estimated by the total area of HPLC peaks at 254 nm and 280 nm in the serum and by the online UV absorbance at 280 nm was best related to the removal of small water-soluble non-protein bound solutes like urea (UR), CR and UA.

CONCLUSIONS

The present study contributes new information on the removal of uremic retention solutes during hemodialysis and on the origin of the optical dialysis adequacy monitoring signal.

Cytotoxicity of mononuclear cells as induced by peritoneal dialysis fluids: insight into mechanisms that regulate osmotic stress-related apoptosis

OBJECTIVE

High glucose content of peritoneal dialysis fluids (PDFs) has been shown to contribute to loss of peritoneal function during long-term peritoneal dialysis. However, hyperosmolality and hypertonicity of PDF are usually seen as similar stress events inducing osmotic stress-induced programmed cell death. In this study, we examined the impact of various osmotic agents on apoptosis induced by hyperosmolar PDFs, focusing on the mechanisms underlying the lethal effects of PDFs on peripheral blood mononuclear cells (PBMCs).

METHODS

We assessed apoptosis and necrosis by annexin V-propidium iodide (PI) labeling, and caspase-3 activity by fluorescence assay. F-actin remodeling was measured using fluorescent phalloidin labeling.

RESULTS

Hyperosmolality does not cause the cytotoxicity observed with PDF, but exposure to agents incapable of permeating cell membranes results in a significant increase in the percentage of apoptotic PBMCs by annexin V-PI labeling, which is confirmed by the increase in caspase-3 activity. Interestingly, inhibition of caspase-3 by Z-VAD-FMK did not suppress apoptosis. Extracellular hypertonicity produced polymerization of filamentous actin and cell shrinkage, which displayed similar time courses. Cell shrinkage was blocked by cytochalasin D, indicating an active role for actin cytoskeleton in hypertonicity-induced cell shrinkage. F-actin polymerization was related to an increase in intracellular ionic strength. Finally, we excluded a direct role for actin remodeling in osmotic stress-induced programmed cell death.

CONCLUSIONS

Exposure to osmolytes that cannot penetrate cell membranes results in a hypertonicity-induced apoptosis that cannot be blocked by the broad-spectrum caspase inhibitor Z-VAD-FMK. In addition, extracellular hypertonicity induced by impermeant solutes produces F-actin polymerization through an increase in intracellular ionic strength. The remodeling of the cytoskeleton does not modulate apoptosis but participates in cell shrinkage.

[Role of genistein in enzymatic albumin hydrolysis in the presence of nitrates (III) and (V)]

Polyphenols and nitrates are essential ingredients of human diet. Harm caused by nitrates is well know and studied. Positive role of polyphenols is investigated. The aim of the study was to analyze interactions between nitrates (III) and (V) and genistein in systems of enzymatic protein (albumin) hydrolysis. In vitro model of enzymatic acidic-alkaline albumine hydrolysis in the presence of nitrates, polyphenols and vitamin C in different concentrations was used. Content of nitrates was measured in dialysation fluid spectrophotometrically according to Griess' method. The study revealed inhibiting influence of genistein on nitrares(III) concentration in external compartment. The influence depended on polyphenol dose (for nitrates (III) between 11.21% and 7.27%, for nitrates (V) between 95.64% and 79.64% of dialysis). When genistein was introduced in too high concentrations--over 2,4 mg/system--it did not improve the effect, but inhibited it. The influence of genistein was synergic with resveratrol and vitamin C.

Peritoneal dialysis solutions low in glucose degradation products--evidence for clinical benefits

In Japan, two types of new peritoneal dialysis fluid (PDF) are ordinarily used: two-chambered PDF, and icodextrin PDF. Two-chambered PDF has several biocompatible characteristics, one being low glucose degradation products (GDPs). Of the several GDPs in PDF, 3,4-dideoxyglucosone-3-ene (3,4-DGE) is thought to be strongly associated with the cytotoxicity of standard PDF. Using a PDF low in GDPs may reduce exposure of the peritoneum to 3,4-DGE, helping to preserve peritoneal function in PD patients. Additionally, use of a PDF low in GDPs may reduce plasma levels of advanced glycosylation end-products in PD patients, a change that may help to preserve vascular function in PD patients. Peritoneal rest for 24 hours after exposure to a PDF with low GDPs improves the activity of human peritoneal mesothelial cells. As compared with the use of standard PDF, the use of low-GDP PDF in combination therapy (peritoneal dialysis plus hemodialysis) may more effectively preserve peritoneal function. The new PDF low in GDPs has biocompatible characteristics relative to peritoneum and system that may help to preserve peritoneal function or reduce complications such as atherosclerosis or dialysis-related amyloidosis in dialysis patients.

[Effect of high glucose-based peritoneal dialysis fluids on NLRP3-IL-1β in human peritoneal mesothelial cells]

OBJECTIVE

To explore the effect of high glucose-based peritoneal dialysis fluids on NLRP3-IL-1β in human peritoneal mesothelial cells.

METHODS

HMrSV5 cells (SV40 immortalized human peritoneal mesothelial cell line) were grown in type I collagen-coated dishes in DMEM/F12 containing 10% fetal calf serum (FCS). All experiments on HMrSV5 cells were performed between passages 5 and 10. The cells were divided into 7 groups: control, 1.5% dextrose, 2.5% dextrose, 4.25% dextrose, rotenone, thenoyltrifluoroacetone (TTFA), and antimycin A. Immunoblotting was used to evaluate the expression of IL-1β. Small interfering RNA (siRNA) targeting NLRP3 was used to downregulate the expression of NLRP3 and Western blot was used to evaluate the expression of IL-1β in human peritoneal mesothelial cells exposed to 4.25% dextrose. In the meanwhile, resveratrol (RSV) was used to induce autophagy, 3-methyladenine (3-MA) and siRNA against Beclin 1 or ATG5 were used to block auto-phagy, flow cytometric was used to analyze the respiring (mitotracker deep red), total (mitotracker green) and reactive oxygen species (ROS)-generating mitochondria (mitoSOX); Western blot was used to evaluate the expression of IL-1β.

RESULTS

The IL-1β relative expressions were 0, 0.175±0.082, 0.418±0.163, 2.357±0.288, 2.642±0.358, 3.271±0.462, and 0.123±0.091, indicating that the cells exposed to high glucose-based peritoneal dialysis fluids and cells treated with mitochondria respiratory chain key enzyme complex I, and complex III inhibitors increased the IL-1β expression. And we found that NLRP3 knock-down significantly blocked the upregulation of IL-1β. In addition, the fluorescence intensity of total mitochondria and ROS-generating mitochondria in the following groups: control, negative control, RSV, 3-MA, ATG5 siRNA, Beclin1 siRNA were 1.76±0.42, 1.83±0.55, 1.85±0.62, 7.36±0.92, 5.35±0.77, 5.06±0.62 and 821.68±95.12, 868.15±102.82, 723.39±92.56, 1 660.08±113.65, 1 433.01±107.24, 1 562.36±112.88 respectively. The increased concentrations of mitochondrial ROS and IL-1β upregulation were confirmed in the inhibition but not the induction of auto-phagy. We also found that downregulation of ATG5 and Beclin1 sensitized cells for the release of IL-1β induced by MSU (monosodium urate) or nigericin which was the NLRP3 inflammasome activator. RSV treatment attentuated this effect.

CONCLUSION

Long-term application of high glucose-based peritoneal dialysis fluids can trigger the consistent activation of NLRP3-IL-1β in peritoneal mesothelial cells. Timely initiation of autophagy may block the NLRP3-IL-1β activation and provide a basis for the further development of a potential therapeutic strategy for delay of chronic inflammation and peritoneal fibrosis associated with peritoneal dialysis.

Prevalence and determinants of low plasma zinc levels in adult peritoneal dialysis patients

OBJECTIVE

Zinc is an essential trace element, being a cofactor for almost 300 enzymes. As zinc is widely available in the diet, the European Best Practice Guidelines do not recommend routine supplementation in dialysis patients. However, some medicines prescribed to dialysis patients may potentially reduce absorption, and there may be increased losses with dialysis. As older and co-morbid patients are now treated by peritoneal dialysis (PD) we wished to determine the prevalence of patients with low plasma zinc levels.

DESIGN AND METHODS

We prospectively measured plasma zinc in 550 PD patients attending for their first peritoneal membrane assessment using atomic absorption spectroscopy. Body composition was determined by bioimpedance.

RESULTS

Plasma zinc was measured in 550 patients, mean age 58.7 years, 60.6% male, mean value 10.8 ± 2.2 umol/L, with 66.5% having low zinc levels (<11.5 umol/L). Normal plasma zinc was associated with haemoglobin (odds ratio (OR) 1.41 (95% confidence limits (95%CL) 1.22-1.63), serum albumin (OR 1.04 (95%CL 1.002-1.087), higher glucose dialysates L/day (OR 1.06 (1.001-1.129), and negatively with 24-hour urinary protein losses (OR 0.786 (95%CL 0.673-0.918) and age (OR 0.985 (95%CL 0.972-1.0). There was no association with dialysis adequacy, original renal disease or dietary protein estimation. Prescription of phosphate binders had no effect on zinc levels (10.7 ± 2.2 vs 10.8 ± 2.3 umol/L).

CONCLUSIONS

Most PD patients had low plasma zinc levels, associated with older age, probably reflecting reduced intake, urinary protein losses, and lower albumin and haemoglobin most likely linked to greater co-morbidity, low grade inflammation and volume expansion requiring higher glucose dialysates.

On the total albumin losses during haemocatharsis

Excessive albumin losses during HC (haemocatharsis) are considered a potential cause of hypoalbuminemia-a key risk factor for mortality. This review on total albumin losses considers albumin "leaking" into the dialysate and losses due to protein/membrane interactions (i.e. adsorption, "secondary membrane formation" and denaturation). The former are fairly easy to determine, usually varying at the level of ~ 2 g to ~ 7 g albumin loss per session. Such values, commonly accepted as representative of the total albumin losses, are often quoted as limits/standards of permissible albumin loss per session. On albumin mass lost due to adsorption/deposition, which is the result of complicated interactions and rather difficult to determine, scant in vivo data exist and there is great uncertainty and confusion regarding their magnitude; this is possibly responsible for neglecting their contribution to the total losses at present. Yet, many relevant in vitro studies suggest that losses of albumin due to protein/membrane interactions are likely comparable to (or even greater than) those due to leaking, particularly in the currently favoured high-convection HDF (haemodiafiltration) treatment. Therefore, it is emphasised that top research priority should be given to resolve these issues, primarily by developing appropriate/facile in vivo test-methods and related analytical techniques.

Viability of, and basic fibroblast growth factor secretion by, human peritoneal mesothelial cells cultured with various components of peritoneal dialysis fluid

In patients on long-term continuous ambulatory peritoneal dialysis (CAPD), peritoneal dysfunction is considered to be due to the loss of peritoneal mesothelial cells and to subsequent peritoneal fibrosis and neovascularization. Our aim in the present study was to clarify the role of various components of peritoneal dialysis fluid in the occurrence of peritoneal dysfunction in CAPD patients. We used a cell counting assay and ELISA to study the viability of human peritoneal mesothelial cells and their secretion of basic fibroblast growth factor (bFGF)--which induces peritoneal fibrosis and neovascularization--by cells cultured with various components of peritoneal dialysis fluid. The viability of cultured cells, ranked from highest to lowest by solution type, was bicarbonate (40 mEq/L) > lactate (15 mEq/L) + bicarbonate (25 mEq/L) > lactate (40 mEq/L). Viability also showed a concentration-dependent decrease in the presence of advanced glycation end-products of bovine serum albumin. The bFGF level in the supernatant showed a concentration-dependent increase in the presence of glucose and glycated albumin; bFGF level decreased as the bicarbonate concentration increased. Low levels of glucose, lactate, and glycated albumin, and a high concentration of bicarbonate may preserve the viability of peritoneal mesothelial cells and prevent bFGF secretion.

[Relative hypoparathyroidism associated with CAPD treatment using normo-calcemic (3.5mEq/1) dialysate: an approach from transperitoneal calcium balance]

We investigated factors affecting net transperitoneal calcium balance (Ca-BL) and the level of parathyroid hormone in relation to stepwise changes in serum calcium, by short PET (peritoneal equibrium test during 240 min: using 2000 ml of 2.5% dextrose dialysate containing 1.75 mmol/L Ca) in uremic patients undergoing stable CAPD. We calculated Ca-BL (mg/effluent/PET) of 244 effluents obtained from 90 patients receiving calcium carbonate as a phosphate binder without vitamin D supplementation. Their serum calcium level corrected with albumin (cSCa), alkaline phosphatase activity (ALP) and intact-PTH level was 9.7 +/- 0.9 mg/dl, 236 +/- 83 mIU/ml and 153.0 +/- 172.4 pg/ml, respectively. We proposed two statistic significant regression lines between Ca-BL and total drainage effluent volume (Ca-BL = 133X - 0.056: r = 0.981, P < 0.001), cSCa (Ca-BL = -12.9X + 123.6: r = 0.941, P < 0.01). Total drainage volume (TDV) and cSCa were two major factors affecting Ca-BL. A TDV level of 2430 ml/240 min-PET or more was required for positive Ca-BL in cases with 9.5-10.0 mg/dl of cSCa, using this linear regression analysis. A cSCa level of 9.6 mg/dl or more was also required for positive Ca-BL in cases with 2400-2600 ml/240min-PET. We also proposed a significant linear regression line between the intact-PTH level and cSCa (i-PTH = -90.5X + 1015.8, r = 0.973, P < 0.01). This line suggest that 200 pg/ml of intact PTH was obtained by 9.0 mg/dl or less of cSCa level in 90 CAPD uremic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of acidity, glucose degradation products, and dialysis fluid buffer choice on peritoneal solute and fluid transport in rats

OBJECTIVE

To evaluate the effects of acidity, glucose degradation products (GDP), and different solution buffer systems on solute and fluid transport during acute peritoneal dialysis (PD) in rats.

DESIGN

Dialysis fluid (16 mL) containing 2.5% glucose as the osmotic agent was instilled intraperitoneally in Wistar rats (280 g) via a thin catheter in dwells lasting 4 hours. Blood and dialysis fluid samples (25 microL) were taken for measurement of glucose, sodium, and radioactive markers. The mass transfer area coefficient (MTAC or PS) for glucose and for 51Cr-EDTA (given as an intravenous infusion) and the peritoneal clearance (Cl) of 125I albumin (RISA), as well as the clearance of RISA to plasma (Cl --> P) were assessed for a commercial, heat-sterilized, acidic PD solution (2.5% glucose, pH 5.5; Gambrosol, Gambro, Lund, Sweden), containing GDP, and for four filter-sterilized solutions containing either lactate (40 mmol/L, pH 5.5 or 7.2), bicarbonate (38 mmol/L, pH 7.2), or pyruvate (40 mmol/L, pH 7.2) as buffers and being devoid of GDP.

RESULTS

The initial pH of the acidic solutions increased rapidly, and attained physiological levels within 40 minutes. The initial drop of sodium, which is expected during the first part of the dwell, was significantly more pronounced with neutral than with acidic lactate. The PS for glucose and 51Cr-EDTA were slightly, but significantly, higher with the acidic and heat-sterilized solution (Gambrosol) than with the neutral, sterile-filtered lactate-buffered solution (p < 0.01), especially early during the dwell. Such an increase may be due to initial vasodilatation, and hence, recruitment of capillaries by the combination of acidity and GDP. However, there were no significant differences with respect to small solute PS values among sterile-filtered solutions, regardless of the presence of acidity or of buffer choice.

CONCLUSION

There were no major differences in fluid and solute transport among sterile-filtered PD solutions having differing buffer systems and pH. Neither were there any effects of GDP alone. However, the combination of a low pH and the presence of GDP in the PD solutions seemed to cause significant increases in peritoneal small solute transport.

Outcome for continuous ambulatory peritoneal dialysis patients is not predicted by peritoneal permeability characteristics

For the present study, we investigated the peritoneal transport of fluid and solutes and the clinical outcomes of 44 continuous ambulatory peritoneal dialysis (CAPD) patients with various peritoneal transport characteristics. Based on 24-hour urine and dialysate collections and 4-hour dwell studies [peritoneal equilibration test (PET)], the patients were divided into two transport groups by dialysate-to-plasma ratio of creatinine at 240 minutes (D/PCr240). The groups consisted of 21 high transporters (D/P = 0.81; mean age: 63.9 +/- 8.2 years) and 23 patients of other transport types (D/P < 0.81; mean age: 67.1 +/- 7.3). Mean CAPD duration was 57.14 +/- 30.4 months and 39.14 +/- 30.4 months respectively (p = 0.07). Estimations were made of weight, body surface area (BSA), percent body water, plasma albumin (PA), Kt/Vurea, weekly creatinine clearance (TCCr), fluid removal, residual renal function, and normalized protein catabolic rate (nPCR). The results showed that high transporters had statistically significant, lower values for: (1) peritoneal fluid (p = 0.02); (2) estimated glomerular filtration rate (GFR: 0.5 +/- 0.77 mL/min vs 2.15 +/- 2.2 mL/min, p = 0.002); and (3) nPCR (0.66 +/- 0.16 g/kg/day vs 0.84 +/- 0.23 g/kg/day, p = 0.003). No statistically significant differences were observed with regard to the other parameters (BSA, PA, Kt/Vurea, TCCr). Cumulative survival rates at two and five years were 90% and 70% for all patients. No statistically significant difference was seen when comparing the survival curves of high transporters and patients of other transport types (p = 0.33, Cox's F-test). In conclusion, we saw no clear evidence that higher peritoneal permeability negatively influences clinical outcome. Other comorbid factors may be related in a more important way to the survival rate for CAPD patients.

Cost-effective dialysis for the developing world

INTRODUCTION

Dialysis is an effective treatment for end-stage renal disease, but it is available to only approximately half of those who need it in the world.

METHODS

Two prototype passive-flow dialysate delivery systems were constructed.

RESULTS

Each dialysate delivery system provided a flow of dialysate in the range of 200-300 mL/minute. In one example, flow regulation was good, but ultrafiltration could not be monitored. The second prototype could monitor and regulate ultrafiltration but required repeated manual adjustment to maintain nearly constant dialysate flow. Approaches to the remaining obstacles to a fully passive dialysis system are outlined, but these will require further work to prove feasibility.

CONCLUSION

In principle, costs of providing hemodialysis could be reduced and equipment created to function without electricity by exploiting passive-flow techniques.

In situ lipolysis measured by in vivo microdialysis during acute cold exposure

The lipolytic responsiveness of interscapular white adipose tissue was measured, in male Sprague-Dawley rats (355 +/- 12 g, n = 7), by microdialysis before, during, and after an acute cold exposure (1 h at 4 degrees C). Microdialysis probes were perfused with standard Krebs-Ringer buffer to determine basal and stimulated rates of lipolysis. The concentration of glycerol in the dialysate was measured and considered as the lipolytic index. During the experiment, energy expenditure was measured by indirect calorimetry. Cold exposure at 4 degrees C doubled energy expenditure. At the same time, it resulted in a 2.7-fold increase in glycerol release. The present study shows that microdialysis is a perfectly adapted tool to investigate in vivo regulation of adipose tissue on awake, unrestrained rats.

Persistent transforming growth factor beta 1 expression may predict peritoneal fibrosis in CAPD patients with frequent peritonitis occurrence

The efficiency of continuous ambulatory peritoneal dialysis (CAPD) depends on the permeability of the peritoneal membrane. Peritoneal fibrosis (PF) causes the loss of dialytic function. Several studies have indicated that PF is closely related to the proliferation of peritoneal fibroblasts and the deposition of extracellular matrix (ECM). Transforming growth factor beta 1 (TGF beta 1) plays a major role in stimulating ECM deposition. Frequent peritonitis occurrence may cause persistent TGF beta 1 mRNA expression. In an attempt to search for a factor related to PF, we designed a longitudinal study to measure TGF beta 1 levels in dialysate and TGF beta 1 mRNA expression in peritoneal mononuclear cells (PMNCs) from peritoneal dialysate before, at the onset of and once a week during peritonitis and after peritonitis in patients with high peritonitis occurrence (HPO) and patients with low peritonitis occurrence (LPO). Fifteen patients with a LPO rate and 5 patients with a HPO rate were followed up longitudinally. Meanwhile, TGF beta 1 levels and TGF beta 1 mRNA expression were augmented in peritoneal dialytic fluid before, during, and after the episodes of peritonitis. Peritoneal permeability was evaluated by the peritoneal equilibration test (PET). The results revealed that in the LPO group, TGF beta 1 and TGF beta 1 mRNA were detectable at early stages of peritonitis, but the levels decreased rapidly and were undetectable 2 weeks after peritonitis. On the other hand, in the HPO group, TGF beta 1 and TGF beta 1 mRNA persisted for a long time. We could detect TGF beta 1 and TGF beta 1 mRNA in dialytic fluid and PMNCs even 2, 3, and 4 weeks after episodes of peritonitis. When compared with that of the first or second episode of peritonitis, peritoneal function evaluated with the PET was found to obviously deteriorate at the third episode of peritonitis. These findings were confirmed by an in situ hybridization technique to evaluate the relationship between TGF beta 1 mRNA expression and PF from biopsied peritoneal specimens. These findings suggest that the high TGF beta 1 levels in the dialysate are related to an increased expression of TGF beta 1 in the peritoneum. Persistent TGF beta 1 expression in the peritoneum may serve as a useful parameter in predicting PF in CAPD patients with frequent peritonitis occurrence.

[The effect of dialysis solutions containing amino acids on the nutritional status of patients treated with continuous ambulatory peritoneal dialysis]

BACKGROUND

In the patient population which is subjected to haemodialysis or peritoneal dialysis is a high prevalence of protein-energy malnutrition which independently on the causal factor causes a deterioration of their prognosis. To influence protein nutrition in patients on peritoneal dialysis Nutrineal was developed, i.e., a dialysis solution using as an osmotic agent a 1.1% amino acid mixture instead of glucose used as a rule. The objective of the present study was to evaluate the effect of its administration on some nutritional indicators in patients treated by continuous ambulatory peritoneal dialysis (CAPD) and to assess its tolerance.

METHODS AND RESULTS

The authors investigated eight patients aged 45.5 years (29-78 years, median, minimal and maximal value), treated for 19.9 (5-42) months by CAPD. For a period of four weeks Nutrineal was administered once a day instead of glucose based solution to patients without diseases complicating nutrition, with a serum albumin concentration (ALB) below 35 (20-34) g/l. Before treatment and after its termination an anthropometric examination was made, the rate of protein catabolism was examined (PCR), plasma concentrations of total proteins were assessed, as well as ALB, transferrin (TRF) and 14 free amino acids substituted by the dialysis solution. For statistical comparison the paired Wilcoxon test was used. As compared with the baseline value of 0.83 g/kg/24 h after treatment a significant increase of PCR was recorded--to 0.96 g/kg/24 h (p < 0.05) as well as a significant increase of the urea concentration from 18.4 (10.9-34.8) mmol/l to 26.7 (19.6-33) mmol/l (p < 0.05). The value of phosphorus declined significantly from 2.25 (1.6-2.6) to 1.9 (0.9-2.5) mmol/l (p < 0.05). No significant difference was recorded in the anthropometric findings and in concentrations of total proteins, ALB, TRF and amino acids.

CONCLUSIONS

Four weeks administration of a solution with amino acids raised significantly the PCR which may be indirect evidence of an anabolic effect and it reduced plasma phosphates which participate in uraemic toxicity. The solution was well tolerated by the patients. Final evaluation of the values of the solution containing amino acids calls for long-term and controlled studies.