Short Term Clinical Study with Bicarbonate-Containing Peritoneal Dialysis Solution

Objective

The evaluation of the efficacy, adequacy, clinical tolerance, and safety of a new bicarbonate continuous ambulatory peritoneal dialysis (CAPD) solution.

Design and Patients

A 6–week cross-over clinical study in 6 stable CAPD patients was performed. After a control period (2 weeks) with a standard CAPD solution (lactate, 35 mmol/L), a two-chamber bag containing 34 mmol/L of bicarbonate was used for 4 weeks. A breakable valve divided the two chambers, one containing bicarbonate and the other calcium. The two solutions were mixed just before use, thus avoiding the calcium and magnesium carbonate precipitation.

Results

No differences between control and study periods were found for blood urea nitrogen, creatinine, total proteins, albumin, total and ionized calcium, phosphate, sodium, potassium, chlorine, and hemoglobin. Blood bicarbonate significantly increased from 21.25±2.02 to 23.36±1.15 (p<0.05) during the study. The peritoneal equilibration tests for urea nitrogen, creatinine, proteins, sodium, potassium, and glucose were slightly reduced during bicarbonate dialysate, but this effect was compensated for by a slight increase of ultrafiltration, thus keeping peritoneal clearances constant. Residual renal function did not change during the study. No side effects occurred during the bicarbonate period.

Conclusion

A CAPD bicarbonate solution is effective in uremic acidosis correction, does not affect dialysis adequacy, is safe, and well tolerated.

Factors Affecting Bicarbonate Transfer with Bicarbonate-Containing CAPD Solution

Objective

To evaluate bicarbonate fluxes across the peritoneal membrane and bicarbonate gain in patients treated with continuous ambulatory peritoneal dialysis (CAPD) using dialysis solutions with different bicarbonate concentrations.

Patients and Design

Ninety-seven exchanges, using different dwell times and glucose and bicarbonate concentrations were performed in 43 stable CAPD patients. Dialysate effluent bicarbonate concentration and volumes were measured at different dwell times. Net dialytic bicarbonate gain was calculated. Patients’ acid-base status was determined at the middle of the dwell.

Results

In prolonged dwells (6 –12 hours)thedialysate effluent bicarbonate concentration correlated with arterial plasma bicarbonate concentration (F = 129, p < 0.0001), but not with ultrafiltration rate or dialysis solution bicarbonate concentration. In 4-hour dwells, effluent bicarbonate concentration correlated with both plasma bicarbonate concentration and ultrafiltration rate (F = 32.52, p < 0.0001 and F = 4.4, p < 0.05, respectively). The effluent bicarbonate concentration may be predicted from the patient's plasma bicarbonate concentration and net ultrafiltration rate for either a 4-hour or prolonged (6 –12 hours) dwell time. Net bicarbonate gain by the patient correlated with ultrafiltration rate, plasma bicarbonate, and dialysis solution bicarbonate concentration (F = 100.56, p < 0.0001 at 4 hours and F = 108.08, p < 0.0001 at 6 12 hours), with the ultrafiltration rate being the predominant parameter.

Conclusions

The effluent bicarbonate concentration is related to plasma bicarbonate concentration, with ultrafiltration playing a marginal role only during short dwells. However, the ultrafiltration rate has a profound effect on net patient bicarbonate gain. Multiple linear regression analysis allows the prediction of the effect of acid-base status, ultrafiltration, dwell time, and dialysis solution bicarbonate content on net patient bicarbonate gain. It seems that bicarbonate content in the CAPD dialysis solution should be progressively increased with increasing solution osmolality.

Fungal Peritonitis in Peritoneal Dialysis: Our Experience and Review of Treatments

From January 1975 to April 1982, 10 of our patients undergoing chronic peritoneal dialysis developed fungal peritonitis. Of six treated without removing the catheter two survived after intraperitoneal (IP) administration of imidazole derivatives, and four died despite combined IP and intravenous (IV) therapy. Of four patients treated by catheter removal, all survived, two without any additional therapy and two after IV antifungal treatment. Three of the deaths followed cardiac or cerebral accidents, while one was related to Candida sepsis.

Bacterial peritonitis is a frequent complication of peritoneal dialysis (FD). In addition fungal peritonitis has been reported with increasing frequency with the growing diffusion of FD, the subsequent increase in infectious episodes, the antibiotic treatment, which such complications require and the improvement in technique for mycological diagnosis.

This paper describes our experience with the clinical manifestations of fungal peritonitis and its treatment in 10 patients undergoing intennittent peritoneal dialysis (IFD) or continuous ambulatory peritoneal dialysis (CAFD).

Pathophysiology of Ultrafiltration in Peritoneal Dialysis

Pathophysiology of peritoneal ultrafiltration is analyzed in the present study. Peritoneal equilibration test is the easiest procedure to study in detail the possible causes of failure to control the ultrafiltration rate in patients undergoing peritoneal dialysis. Membrane failure, reduction in peritoneal blood flow, excessive lymphatic reabsorption catheter malposition, and fluid sequestration are the most common causes of ultrafiltration loss. Pharmacologic manipulation of peritoneal membrane, correction of mechanical inconvenients, reduction in peritonitis rate and in the level of immunostimulation of the mesotelial macrophages, together with a careful policy in terms of glucose concentration in the dialysate and dwell times may contribute not only to treat different forms of ultrafiltration loss but also to prevent their incidence.

Acid-Base Balance with Different Capd Solutions

Our objective is to investigate transperitoneal buffer fluxes with solution containing lactate and bicarbonate, and to compare the final effect on body base balance of the two solutions.

One hundred and four exchanges, using different dwell times, were performed in 52 stable continuous ambulatory peritoneal dialysis (CAPD) patients. Dialysate effluent lactate and bicarbonate and volumes were measured. Net dialytic base gain was calculated. Patients’ acid-base status and plasma lactate were determined.

In lactate-buffered CAPD solution, lactate concentration in dialysate effluent inversely correlated with length of dwell time, but did not correlate with plasma lactate concentration and net ultrafiltration. Bicarbonate concentration in dialysate effluent correlated with plasma bicarbonate and dwell time but not with ultrafiltration.

The arithmetic sum of the lactate gain and bicarbonate loss yielded the net dialytic base gain. Ultrafiltration was the most important factor affecting net dialytic base gain.

A previous study demonstrated that in patients using a bicarbonate-buffered solution the net bicarbonate gain is a function of dwell time, ultrafiltration, and plasma bicarbonate.

By combining the predicted data of the dialytic base gain with the calculated metabolic acid production, an approximate body base balance could be obtained with both lactate and bicarbonate-buffered CAPD solutions.

The body base balance in CAPD patients is self-regulated by the feedback between plasma bicarbonate concentration and dialytic base gain. The level of plasma bicarbonate is determined by the dialytic base gain and the metabolic acid production. This can explain the large interpatient variability in acid-base correction. Bicarbonate-buffered CAPD solution is equal to lactate solution in correcting acid-base disorders of CAPD patients.

Clinical Experience with a 39 Mmol/L Bicarbonate-Buffered Peritoneal Dialysis Solution

Objective

To investigate the effect on the patient's acidbase status of a 39 mmol/L bicarbonate-buffered continuous ambulatory peritoneal dialysis (CAPD) solution.

Design

This was an open, controlled, cross-over, two-center study in 9 patients. After three months of treatment with a 34 mmol/L bicarbonate-buffered solution (to) patients were switched to a 39 mmol/L bicarbonate-containing solution for four weeks. At the end of the study period (t4) patients were again treated with a 34 mmol/L bicarbonate-buffered CAPD solution for one month (t8).

Results

Mean venous plasma bicarbonate level significantly increased during the study and decreased at the baseline level during the control period (to = 22.94±2.54, t1 = 26.74±3.07, t2=28.47±2.68, t3=28.11±3.56, t4=28.71±3.27, t8=24.94±2.56). Arterial blood pH and plasma bicarbonate significantly increased during the study and significantly decreased attheend of the control period (pH: to= 7.37±0.04, t4= 7.42±0.04, t8= 7.37±0.06. Bicarbonate: t0= 21.97±2.57, t4= 25.85±2.02, t8= 21.87±2.89). The changes in plasma bicarbonate during the study period were inversely correlated with the metabolic acid production calculated from the protein catabolic rate and with the apparent distribution space for bicarbonate (ABS) of patients.

Conclusions

The 39 mmol/L bicarbonate-buffered CAPD solution improved the patient's acid-base status. Potential undesirable metabolic alkalosis could be prevented by analyzing the ABS and the metabolic acid production of patients.

Impacts of agricultural practices on pyrethroid resistance in Culex pipiens pipiens, an important vector of human diseases, from Tunisia

Agricultural pesticides may play a profound role in selection of resistance in field populations of mosquito vectors. The aim of the present study was to examine the relationship between agricultural pesticide use and development of resistance to insecticides in Culex pipiens pipiens from Tunisia. Entomological surveys were conducted in three various districts from Tunisia differ in insect control in agriculture and in public health. A reference locality without any chemical activities was used to do different comparisons. Our results revealed that the level of permethrin resistance ranged from 40.9 to 7438. Practically no susceptible populations were found and resistance to permethrin was important, but significantly higher in site submitted to both agricultural and public health applications. However, resistance ratio has been decreased 7000 folds in site not submitted to agricultural pests. These observations expressed an important influence of agricultural applications on permethrin resistance and need an urgent coordination between the integrated vector control program and the Ministry of Agriculture to reduce the development of resistance in populations. The recorded resistance was slightly associated with DDT suggest the involvement of their common mechanism (target site). Synergist's tests indicated that different enzymes played an important role in the detoxification of this insecticide.

Characterization of resistance to pirimiphos-methyl (an organophosphate insecticide) in Culex pipiens pipiens (Diptera: Culicidae) from Northern and Southern Tunisia

Despite the public health importance of Culex pipiens pipiens, their resistance to pirimiphos-methyl insecticides has not been explored enough. Late third and early fourth larvae of Culex pipiens pipiens were collected from three localities between 2003 and 2005 in Northern and Southern Tunisia. All bioassays were carried out using pirimiphosmethyl and propoxur insecticides. Populations of Culex pipiens pipiens were susceptible, moderate and resistant to pirimiphos-methyl insecticide. Resistance to this compound ranged from 2.62 in sample # 2 to 19.9 in sample # 1. The moderate resistance (5.25) was recorded in sample # 3. Synergist's tests showed that the resistance to pirimiphos-methyl was not affected by detoxification enzymes. However, biochemical assays showed the involvement of both metabolic (esterases) and target site (insensitive acetylcholinesterase) resistance mechanisms. The highest frequencies of the resistant phenotypes ([RS] and [RR]) (<0.74) were detected in the most resistant samples (#1). Four esterases enzymes including C1 encoded by the Est-1 locus and three esterases encoded by the Ester super locus: A2-B2, A4-B4 (or A5-B5, which has the same electrophoretic mobility) and B12 were detected. The highest (0.61) and the lowest (0.22) frequencies of these esterases were recorded in samples # 1 (Sidi Hcine) and # 2 (El Fahs) which recorded the highest and the lowest level of resistance, respectively. Monitoring of insecticide resistance should be evaluated regularly for management of vector control.

Multiple resistance mechanisms associated with low pirimifos-methyl resistance in Culex pipiens pipiens in three populations of Tunisia

The aim of this study was to evaluate the resistance status of Culex pipiens pipiens to pirimiphos-methyl insecticide. Three field populations of mosquitoes were collected from Tunisia and analyzed in laboratory. The samples studied showed low level of resistance not exceeding 5-folds. The low resistance recorded is particularly interesting, because it leaves a range of tools useable by vector control services. Both metabolic and target-site resistance mechanisms were identified. Different esterases of high activity including A2-B2, A4-B4 (and/or A5-B5) and B12 were observed in studied field samples using starch electrophoresis although opposite results were found using synergists tests on samples # 1 and 3. The polymorphism of AChE1 (Acetylcholinesterase) was analyzed and three phenotypes were detected: susceptible (ACHE1S, phenotype [SS]), resistant (ACHE1R, phenotype [RR]), and heterozygous (phenotype [RS]) of ACHE1. The resistance of Culex pipiens pipiens to pirimiphos-methyl remains low although the occurrences of multiple resistance mechanisms are able to confer high resistance levels to organophosphate insecticides. Therefore, continuous monitoring of resistance is fundamental for rational use of insecticides and mosquito control programs.

Different Buffers for Hemodiafiltration: A Controlled Study

Hemodiafiltration (HDF) is usually performed using a dialytic solution (D) containing acetate (A) or bicarbonate (B) and a replacement fluid (RF) containing lactate (L).

To clarify the role of buffers in HDF, 11 patients underwent different study periods, each three months long: bicarbonate hemodialysis (BHD = Baseline period); HDF with (A) in D and (L) in RF (first period of HDF); HDF with (A) in D and (B) in RF (second HDF); HDF with (B) in D and (L) in RF (third HDF); HDF with (B) in D and (B) in RF (fourth HDF = BHDF).

HDF achieved: 1) an increase in dialytic efficiency (kt/V, 1.28), reducing the time-session (197 min); 2) an improvement in acid-base status (pre-dialytic values in BHDF: pH 7.36; pCO2 39.8 mmHg; HCO−3 21.8 mM/L); 3) better “dry weight” gain (reached in 92.8% of HDF and in 81% of BHD sessions); 4) a significant decrease, in dialytic side-effects (mainly during the third and fourth periods).

On the whole, BHDF (HDF done using only bicarbonate buffer) represents an easy and safe technique, leading to better cardiovascular stability than BHD and HDF without bicarbonate buffer.

Comparison of Four Different Short Dialysis Techniques

The goal of shortening dialysis treatment time has stimulated the development of new, highly efficient dialytic strategies. In this study the Authors compared four different short dialysis treatments in terms of efficiency, clinical tolerance, technological investment and costs: 1) Rapid bicarbonate dialysis with 1.5 sq.m. cuprophane membrane; 2) High flux biofiltration with 1.2 sq.m. AN69S hollow fiber membrane; 3) Hemodiafiltration with 1.2-1.9. sq.m. polysulphonic hollow fiber hemodiafilters, and 4) High flux hemodiafiltration with two serial hemodiafilters with AN69s membrane (total 2.4 sq.m.).

Hydraulic properties and solute clearances at different blood flows (300-500 ml/min) were tested for each technique. Once the optimal operative level was established three patients were treated with each technique for at least six months. Since BUN clearance averaged 310 ml/min, the treatment duration varied from 120 to 180 min/session with KT/V always higher than 1. The average protein catabolic rate was 0.9 g/kg/24h. Clinical tolerance was generally good, slightly better in treatments with a high convective component. Despite the greater efficiency of treatment No. 4, the technological requirements and costs are such that the others are currently more feasible and acceptable in clinical routine.

The study demonstrates that reduction of dialysis treatment time is possible in all centres in a selected population with adequate blood access. Treatment No. 1 can even be performed with standard equipment and cuprophan membranes, while bicarbonate in the dialysate is mandatory. The real limit to shortening treatment time seems to be related to the maximal rate of ultrafiltration achievable in the patient during dialysis.

Anatomical Bases of Peritoneal Permeability: A Reappraisal. Anatomy of Peritoneum

The peritoneal membrane consists of flat mesothelial cells linked together with digitations and containing vesiculae with pinocytic capacity, of endothelial cells (containing Weibel-Palade's bodies and vesiculae) and of an interstitial tissue consisting of a network of watery channels.

The cellular structures of mesothelium and endothelium are characterized by tight and gap junctions or perhaps by macular junctions. The visceral peritoneum shows a prevalence of gap junctions, the pericytic veins contain only tight junctions while both types can be found in the arterioles.

Two different ways for solute transport are theoretically possible: the vesicles of plasmalemma (via pinocytosis) and the junctions (via size-sieving effect). Studies with tracers did not furnish unequivocal data on this problem and did not clarify if these structures could be the equivalent of the pores of the Landis-Pappenheimer's theory. The studies of Karnowsky and Simionescu, using tracers, have in fact given opposite results.

The role of Neurotransmitters in the Genesis of Uremic Encephalopathy

To classify the influence of neurotransmitters in the genesis of uremic encephalopathy we studied cerebrospinal fluid (CSF) and plasma (P) amino acid (AA) concentration, in patients undergoing various dialytic treatments (hemodialysis = HD, intermittent and continuous peritoneal dialysis = IPD and CAPD).

HD causes a significant decrease in CSF/P ratios of branched chain AA (BCAA) and a significant increase in CSF Glycine/Valine ratio, suggesting an augmented brain uptake of Glycine at detriment of Valine. In IPD the general trend of Aromatic AA/BCAA ratio suggests a preferentilal transport of Aromatic AA through the blood brain barrier. The differences between IPD and HD are confirmed by data concerning metabolites of Serotonin and Dopamine: CSF concentrations of 5-Hydroxyndoleacetic acid and Homovanillic acid are low in HD but high in IPD.

So, a reduced (in HD) and an increased (in IPD) activity of monoamine systems could be at the basis of some neurological disturbances appearing in uremia.

Technical and clinical evaluation of a new polyamide hollow fiber hemofilter for CAVH

We carried out an in-vivo and in-vitro evaluation of a new polyamide hollow fiber hemofilter especially designed to operate under conditions of low pressure and low blood flow, such as in continuous arteriovenous hemofiltration (CAVH).

The results obtained suggest that this filter is a prototype of a new generation of hemofilters especially designed for CAVH. Its low resistance permits its use even in patients with severe hypotension. The high blood flows achieved at a given pressure reduce the risk of clotting and increase the ultrafiltration rate. When an average ultrafiltration of 20-25 ml/min is achieved in 24 hours CAVH becomes very efficient, and alternative techniques to increase its efficiency are no longer required.

Hyperprolactinemia as a Marker of Neurotransmitter Imbalance in Uremic Population

Serum prolactin (PRL) levels are elevated in patients with chronic renal failure (CRF) but the mechanisms responsible for these abnormalities are not fully understood. PRL secretion is undoubtedly influenced by many substances, which can be variously altered in uremia: monoamines, endogenous opiates and PTH. Our data suggest that in early renal failure PRL levels are already significantly high and the 24-h pattern of PRL secretion is significantly different from that in controls.

PRL derangements could be due in mild renal failure, to unknown factors (GABA?); in severe CRF, to a major change in dopaminergic activity; in hemodialysis (HD), to a low turnover of monoamines, and in peritoneal dialysis (PD) to increased activity of sero-toninergic and dopaminergic systems.

Solute and Water Transport during Continuous Arteriovenous Hemofiltration (CAVH)

The transport mechanisms governing solvent and solute removal during CAVH were elucidated on the basis of in vitro and in vivo observations.

Using a typical hemofilter (Diafilter D-20, AMICON), filtration rate rose with inlet blood flow rate until an asymptote was reached at blood flows of approximately 150 ml/min. The onset of the asymptote coincided with transition from a regime controlled by oncotic pressure (filtration pressure equilibrium), to one governed by simple Darcy's law filtration behaviour. Subsequent measurements showed that under clinical conditions, CAVH is generally in the pre-asymptotic regime and operates at filtration pressure equilibrium.

These observations offer the theoretical bases for a new design for CAVH hemofilters.

As a possible corollary, middle-molecule sieving coefficients were found to be stable with time during CAVH in vivo, whereas in chronic mechanical hemofiltration they declined significantly during clinical treatment. The sieving coefficients, however, were lower in mechanical hemofiltration from the beginning of the session.

These observations suggest that the measured sieving coefficient for a membrane is not necessarily a constant directly and solely related to the membrane standard reflection coefficient for a given solute. Concentration polarization and the ultrafiltration rate per unit of surface area may in fact have a major effect on the final concentration of solutes in the ultrafiltrate.

Dynamic Catheterography in the Early Diagnosis of Peritoneal Catheter Malfunction

The dynamic catheterography is an imagin technique that allows to study the peritoneal solution inflow and outflow phases in case of catheter malfunction. The examination is carried out in three subsequent steps: 1) direct examination without contrast media in order to define the position of the catheter inside the abdomen; 2) low speed catheterography by normal injection of 10 ml of hydrosoluble contrast medium to verift the patency of the cannula; 3) high speed catheterography by 30 ml hydrosoluble dye injected with an automateds high pressure system to study the inflow phase, the fluid distribution in the peritoneal cavity and the patency of the catheter holes. Different radiographic patterns can be found: dislocation of the catheter tip, KinKing, one way obstruction, inner lumen obstruction. The procedure is simple, safe and reliable for a correct diagnosis and for the choice of a successfull therapeutic approach to peritoneale catheter malfunction.

A New Blood Module for Continuous Renal Replacement Therapies

A new blood module for continuous renal replacement therapies has been utilized to perform CVVH in critically ill patients. The features of the new module named (HP300 and manifactured by Medica srl (Medolla, Modena) are the easy installation and transportability to the bedside, the simple and safe management and the continuous measurement of the pre and post filter pressure with automatic calculation of the end-to-end pressure drop inside the filter. The last feature permits to detect early malfunctions of the filter due to fibers clotting or due to the internal coating of the hollow fibers by plasma proteins. In both cases the efficiency of the treatment can be reduced because of a significant reduction of the ultrafiltration rates or a remarkable decay of the membrane permeability and solute sieving coefficients. In many cases this reduction is only detected when important effects on solute removal have already occurred. In our experience, the new module permitted the substitution of the filters when early malfunctions were detected and maximal treatment efficiency was therefore guaranteed over extended periods of time.

Effect of balance Solution on the Peritoneal Membrane in Automated Peritoneal Dialysis

Interference of conventional peritoneal dialysis fluids (cPDFs) with peritoneal membrane cell functions may be attributed to the dialysis fluid's low pH, high glucose concentration, and/or the presence of glucose degradation products (GDPs), the last of which leads to higher levels of advanced glycation end-products (AGEs). It has been suggested that the peritoneal membrane might be better preserved by using biocompatible solutions, including cancer antigetn 125 (CA125). This prospective, open-label, multicentre, randomized, controlled, cross-over phase IV study compared the in vivo biocompatibility of a neutral-pH, low-GDP peritoneal dialysis (PD) solution (balance) with a cPDF in automated PD (APD) patients. Our study revealed a significantly increased appearance rate and concentration of CA125 in the peritoneal effluent of APD patients treated with the neutral-pH, low-GDP solution balance versus a conventional PD solution.

Peritoneal Equilibration Test Reference Values Using A 3.86% Glucose Solution during the First Year of Peritoneal Dialysis: Results of a Multicenter Study of a Large Patient Population

Background

The original peritoneal equilibration test (PET) was used to classify peritoneal dialysis (PD) patients using a 2.27% glucose solution. It has since been suggested that a 3.86% glucose solution be used because this provides better information about ultrafiltration (UF) capacity and the sodium (Na) sieving of the peritoneal membrane.

Objective

The aim of this study was to determine reference values for a PET using a 3.86% glucose solution (PET-3.86%).

Methods

We evaluated the PET-3.86% in a large population of incident PD patients attending 27 Italian dialysis centers.

Results

We evaluated the results of 758 PET-3.86% in 758 incident PD patients (1 test per patient). The mean duration of PD was 5 ± 3 months. The ratio of the concentrations of creatinine in dialysate/plasma (D/PCreat) was 0.73 ± 0.1 (median 0.74). The ratio between the concentrations of glucose at the end/beginning of the test (D/D0) was 0.25 ± 0.08 (median 0.24). Ultrafiltration uncorrected and corrected for bag overfill was respectively 776 ± 295 mL (median 781 mL) and 675 ± 308 mL (median 689 mL). Sodium sieving was 8.4 ± 3.8 mmol/L (median 8.0 mmol/L).

Conclusion

The results of the study provide PET-3.86% reference values for the beginning of PD that can be used to classify PD patients into transport classes and monitor them over time.

[Peritonitis and catheter-related infections in peritoneal dialysis]

The incidence of peritoneal dialysis-related infections has decreased markedly over the past 20 years. This is commonly believed to be the result of improvements in connection technology and eradication of nasal and exit-site Staphylococcus aureus. However, peritonitis is still the most important cause of technique failure. The good results of single centers with a long experience of peritoneal dialysis and the excellent randomized trial results have proved to be incomparable with those of nonselected populations. The analysis of organism-specific infections joined to the identification of the entry pathway into the peritoneum could allow individual centers to focus on the weaknesses of the used protocols and procedures.

Twenty years of bicarbonate solutions

For many years, lactate has been used successfully as a buffer in peritoneal dialysis solutions although its effectiveness in the correction of uremic acidosis and its biocompatibility on peritoneal resident cells have been questioned. In addition, some investigators have suggested other potential adverse metabolic effects resulting from the unphysiologically high lactate flux into the body during CAPD. These potential problems associated with lactate-containing CAPD solution prompted the search for alternative buffer-containing solutions. Bicarbonate, the physiological buffer, was considered when the problem of calcium and magnesium carbonate solubility was solved by the use of a two-compartment bag system allowing the mixing of bicarbonate and divalent cations immediately before infusion. The long-term tolerance, safety, efficacy and therapeutic value of a bicarbonate-buffered peritoneal dialysis solution have been evaluated for about 15 years. RCT studies demonstrated a benefit for acid base improvement, while observational reports showed other clinical effects such as a preservation of residual renal function, less inflammatory effect and peritonitis prevention. In addition, there is a consensus that local biocompatibility is improved. Therefore, as bicarbonate is the physiological buffer of the body, it should become the solution of choice in PD patients.

Predictors of haemoglobin levels and resistance to erythropoiesis-stimulating agents in patients treated with low-flux haemodialysis, haemofiltration and haemodiafiltration: results of a multicentre randomized and controlled trial

Background

Predictors of haemoglobin (Hb) levels and resistance to erythropoiesis-stimulating agents (ESAs) in dialysis patients have not yet been clearly defined. Some mainly uncontrolled studies suggest that online haemodiafiltration (HDF) may have a beneficial effect on Hb, whereas no data are available concerning online haemofiltration (HF). The objectives of this study were to evaluate the effects of convective treatments (CTs) on Hb levels and ESA resistance in comparison with low-flux haemodialysis (HD) and to evaluate the predictors of these outcomes.

Methods

Primary multivariate analysis was made of a pre-specified secondary outcome of a multicentre, open-label, randomized controlled study in which 146 chronic HD patients from 27 Italian centres were randomly assigned to HD (70 patients) or CTs: online pre-dilution HF (36 patients) or online pre-dilution HDF (40 patients).

Results

CTs did not affect Hb levels (P = 0.596) or ESA resistance (P = 0.984). Hb correlated with polycystic kidney disease (P = 0.001), C-reactive protein (P = 0.025), ferritin (P = 0.018), ESA dose (P < 0.001) and total cholesterol (P = 0.021). The participating centres were the main source of Hb variability (partial eta² 0.313, P < 0.001). ESA resistance directly correlated with serum ferritin (P = 0.030) and beta2 microglobulin (P = 0.065); participating centres were again a major source of variance (partial eta² 0.367, P < 0.001). Transferrin saturation did not predict either outcome variables (P = 0.277 and P = 0.170).

Conclusions

In comparison with low-flux HD, CTs did not significantly improve Hb levels or ESA resistance. The main sources of variability were participating centres, ESA dose and the underlying disease.

Extended dosing of darbepoetin alfa in peritoneal dialysis patients

BACKGROUND

Anemia is common among peritoneal dialysis (PD) patients, and most patients require erythropoiesis-stimulating agents (ESA) to maintain their hemoglobin concentrations within current guideline recommendations. Darbepoetin alfa is an ESA with a 3-fold longer half-life and greater in vivo biological activity than recombinant human erythropoietin, allowing less frequent dosing that may simplify anemia management in these patients, providing benefits to patients, care givers and health care providers. Clinical studies have confirmed the efficacy and safety of darbepoetin alfa administered at extended dosing intervals. However, there are limited data on the management of anemia with ESAs in PD patients in routine clinical practice. The aim of this multicenter observational study in European and Australian dialysis patients was to evaluate darbepoetin alfa administered once every 2 weeks (Q2W) in routine clinical practice for 12 months.

METHODS

PD patients ≥18 years old and converting to treatment with darbepoetin alfa Q2W were eligible for enrollment regardless of previous or current ESA use. Patients enrolled in the study were treated according to local usual clinical practice. Data were collected up to 6 months prior to and 12 months after conversion to darbepoetin alfa Q2W. The primary endpoint was hemoglobin concentration 12 months after conversion to darbepoetin alfa Q2W.

RESULTS

Of the 741 eligible PD patients (mean age, 61 years; male, 57%), 640 (86%) completed the study. Mean hemoglobin concentration (g/dL) was 11.69 (95% CI, 11.53-11.86) 6 months before the conversion, 12.25 (95% CI, 12.13-12.38) at conversion, and 11.88 (95% CI, 11.74-12.02) 12 months after conversion to darbepoetin alfa Q2W. The weekly equivalent ESA dose (μg/wk) was a geometric mean of 25.24 (95% CI, 23.46-27.15) 6 months before conversion, 20.90 (95% CI, 19.13-22.83) immediately before conversion, 18.89 (95% CI, 18.13-19.68) at conversion and 19.04 (95% CI, 17.69-20.49) 12 months after conversion. Twelve months after conversion, 70% of patients were receiving darbepoetin alfa Q2W and 73% had hemoglobin concentrations >11.0 g/dL.

CONCLUSION

In this large observational study, PD patients were able to maintain mean hemoglobin concentrations >11.0 g/dL after conversion to extended dosing of darbepoetin alfa Q2W, with no mean dose increase.

Molecular biology-based assessment of vitamin E-coated dialyzer effects on oxidative stress, inflammation, and vascular remodeling

Cardiovascular disease represents the most common cause for the excess of morbidity and mortality found in end-stage renal disease (ESRD) and has prompted the exploration of multiple approaches to improve outcomes in these patients. Cardiovascular risk factors such as increased oxidative stress (OxSt) and inflammation are found in ESRD patients. A vitamin E-coated dialyzer using polysulfone membranes has been suggested to have positive effects on these factors. This 1-year study evaluated in 25 ESRD patients under chronic dialysis, the effects of a vitamin E-coated membrane (VitabranE ViE) "ex vivo" on mononuclear cells, OxSt, and inflammation-related biochemical and molecular biology markers using a molecular biology approach. p22(phox), heme oxygenase (HO)-1, plasminogen activator inhibitor (PAI)-1 protein level, and phosphorylated extracellular signal-regulated kinase (pERK)1/2 status were evaluated at the beginning of the study, after 6 months and after 12 months by Western blot analysis and oxidized low-density lipoprotein (OxLDL) plasma level by enzyme-linked immunosorbent assay, alongside vascular remodeling assessment as measured by carotid intima-media thickness (IMT) in a subgroup of nine randomly selected patients. p22(phox), PAI-1, OxLDL, and pERK all decreased with VitabranE use, while HO-1 increased. Carotid IMT did not increase. Treatment with VitabranE significantly decreases the expression of proteins and markers relevant to OxSt and inflammation tightly associated with cardiovascular disease, and it appears highly likely that VitabranE use will provide a benefit in terms of cardiovascular protection.

Hemofiltration and hemodiafiltration reduce intradialytic hypotension in ESRD

Symptomatic intradialytic hypotension is a common complication of hemodialysis (HD). The application of convective therapies to the outpatient setting may improve outcomes, including intradialytic hypotension. In this multicenter, open-label, randomized controlled study, we randomly assigned 146 long-term dialysis patients to HD (n = 70), online predilution hemofiltration (HF; n = 36), or online predilution hemodiafiltration (HDF; n = 40). The primary end point was the frequency of intradialytic symptomatic hypotension (ISH). Compared with the run-in period, the frequency of sessions with ISH during the evaluation period increased for HD (7.1 to 7.9%) and decreased for both HF (9.8 to 8.0%) and HDF (10.6 to 5.2%) (P < 0.001). Mean predialysis systolic BP increased by 4.2 mmHg among those who were assigned to HDF compared with decreases of 0.6 and 1.8 mmHg among those who were assigned to HD and HF, respectively (P = 0.038). Multivariate logistic regression demonstrated significant risk reductions in ISH for both HF (odds ratio 0.69; 95% confidence interval 0.51 to 0.92) and HDF (odds ratio 0.46, 95% confidence interval 0.33 to 0.63). There was a trend toward higher dropout for those who were assigned to HF (P = 0.107). In conclusion, compared with conventional HD, convective therapies (HDF and HF) reduce ISH in long-term dialysis patients.

[The Veneto Region's Registry of Dialysis and Transplantation: 2006-2007 report]

INCIDENCE

Five hundred and sixty patients began renal replacement therapy in 2006, giving an incidence of 117.51 pmp; in 2007 there were 579 new patients, for an incidence rate of 120.01 pmp. Analysis of the incidence between 1998 and 2007 for both raw and age-standardized data (based on the 2001 census) shows a slow, gradual increase that is statistically significant. Most of the patients were between 55 and 85 years old; the modal class for males was between 65 and 70, and between 75 and 80 for females. The median age of the population beginning replacement therapy is clearly over 65 years old. The year 2000 was particularly significant because the incidence of new patients undergoing renal replacement therapy over the age of 75 definitively exceeded that of the next younger class (65-74 years old), a trend that remained constant until 2007. In 2006 and 2007, males account for 64.4% and 66.4%, respectively, of new patients, a proportion that is constant over the years. The greater incidence of males is also to be found across the other age groups and tends to be even more noticeable in the oldest age class. Incidence by province is highly variable, however, there is a constant trend within provinces during these years, since the incidence in some provinces is lower than the regional average and higher in others. After adjusting for age, there are no significant differences in the incidence between provinces: the age structure of the population accounts for the variability of the incidence of terminal uremia across the Veneto provinces. The conditions most responsible for renal insufficiency requiring replacement therapy are vascular diseases, diabetes and nephropathies of unknown origin. Although diabetic and vascular nephropathies are subject to wide fluctuations, they remain stable over the years, whereas the frequency of nephropathy of unknown origin appears to be on the rise. The first treatment for most of the patients is hemodialysis. In 2006, 436 patients (78%) were given extracorporeal dialysis as first treatment, compared to 122 patients (22%) who were given peritoneal dialysis and 2 (0.35%) who received live-donor kidney transplant. In 2007 the situation was very similar, with 435 patients treated with extracorporeal dialysis, 142 with peritoneal dialysis and 1 by a live-donor transplant. The proportion between patients treated with hemodialysis and peritoneal dialysis was constant from 1998 to 2007. The choice between hemodialysis or peritoneal dialysis as the initial treatment modality depends on many factors, ranging from clinical indications to cultural attitudes at the facility to individual patient preferences. Logistic regression of the factors influencing the choice of dialysis treatment shows that peritoneal dialysis is offered primarily to patients between the ages of 45 and 65 who do not have an underlying systemic or nephropathy of unknown origin and who do not have any comorbidities. This confirms the positive selection made with regard to these patients, widely described in the literature. Initial treatment by transplant is an exceptional event: starting from 2003, it was used in only 1 or 2 patients per year. Seventy-two percent of patients starting replacement therapy present with at least one comorbidity. Thirty-six percent of patients also present with more than one associated disease. The RVDT has been gathering data on the vascular access used for new dialysis patients since 2006. Roughly 43% of patients start treatment with an arteriovenous fistula, 38% with a temporary catheter, less than 1% with a prosthesis, 9% with a tunneled catheter, and 10% with a peritoneal catheter. Logistic regression was used to evaluate what role age, primary nephropathies and comorbidities present at the start of treatment play in determining the choice of a temporary catheter. The logistic model estimates a 29% probability of starting treatment with a temporary access. This probability decreases if the patient suffers from a familiar or hereditary nephropathy but increases if the patient has secondary glomerulonephritis or is affected by a group of various diseases (multiple myeloma or other pathologies) or if the patient suffers at the same time from cardiac insufficiency or an infection. The estimated probability of starting hemodialysis with a mature fistula is 40%, but this figure diminishes significantly in female patients, if the patient has secondary glomerulonephritis, cardiac insufficiency or infections.

PREVALENCE

As of December 31, 2006, there were 4,071 patients being treated with extracorporeal or peritoneal dialysis or by kidney transplant, leading to a prevalence of 852.82 patients pmp; as of December 31, 2007, there were 4,200 patients treated, with a corresponding prevalence of 869.14 pmp. The breakdown in prevalence by age group shows that the increase in prevalence is highly significant in the top two age classes, namely, between 65 and 75 years of age and over 75, while remaining negligible in the other classes. Between 1998 and 2007, the prevalence increased by 40% in patients over 75 and increased by 20% in the class of 65-to-75 year olds. The elderly contribute a greater weight in the renal replacement therapy population, reflected in the gradual increase of the median age of the prevalent population from 1998 to 2007. During 2006 and 2007, males made up 63.99% and 64.36% of the patients, respectively. This relative frequency mirrors the findings for incidence and is constant over the years. The distribution of primary diseases is very different in the prevalent population compared to findings in the incident patients. Primary glomerulonephritis, at fourth place among incident patients, is the most frequent disease in the prevalent population (although there is a clearly downward trend over the years). The percentages of diabetes and vascular disease, on the other hand, are lower compared to what is observed in the incident population. The prevalence expressed by treatment modality pmp increased for all three types. In analyzing the annual percentage rise in prevalence, using 1998 as the baseline, the most significant figure regards transplant patients, whose prevalence increased by over 60% between 1998 and 2007. Prevalence of hemodialysis patients rose moderately by only slightly over 10%. Peritoneal dialysis shows a rather linear increase, similar to the transplant trend. Our study used longitudinal regression models to analyze factors predictive of a patient starting and continuing to undergo the same type of treatment over the years. The results show that a patient has a greater probability of being treated with hemodialysis based on several primary nephropathies, when aged > 45, and in the presence of the main comorbidities. The predictive factors for peritoneal dialysis mentioned earlier have a diametrically opposed role. The presence of comorbidities (except high blood pressure), the type of nephropathy, and age > 65 lead to a lower probability of receiving a transplant. We analyzed peritoneal dialysis failures - defined as changing over to extracorporeal dialysis for any reason (clinical, psychological or social) - and the cumulative incidence of failure, taking into account the two competing outcomes of transplant and death. The only variable associated with peritoneal dialysis failure was the presence of infections. Older patients, patients with peripheral vascular disease, and those with neoplasia are less frequently taken off peritoneal dialysis to receive a transplant, an event occurring more frequently, however, in patients with hypertension. Death is dependent on age, on the presence of peripheral vascular disease and is less frequent in hypertensives. As is the case for peritoneal dialysis, the natural history of kidney transplant can have two competing outcomes: return to dialysis and death. The risk factors associated with return to dialysis are the presence of peripheral vascular disease, hypertension and infections; risk factors associated with death include age, the presence of cerebral vascular disease and neoplasia. From 1998 to 2007, the prevalence of hepatitis C virus-antibody-positive patients decreased by almost one third. The number of antigen-positive hepatitis B patients is declining slowly, but the levels remain in any case very low. The association between the two infections is disappearing: already at very low levels in 1998, that figure was halved by 2007. MORTALITY AND SURVIVAL: The mortality of uremic patients on renal replacement therapy was calculated both as a cumulative incidence, expressed as the number of deaths over patients at risk (alive at the beginning of the study year) and as a mortality rate, expressed as the number of deaths per patients/year. The figure was constant over the years, at around 10%. The mortality of males was no different from that of females; this finding differs from what is observed in the general population where male mortality is markedly higher than that of females. The mortality rate is dependent on the age group of the patient at start of treatment and shows an upward trend that is growing exponentially. The mortality rate in hemodialysis patients remained stable at 15% between 2000 and 2007, while the mortality rate in peritoneal dialysis patients gradually decreased down to 13%. The mortality rate for transplant patients was low and constant, at under 2%. The trend for the various causes of death is stable over the years and shows that the main cause of death is cardiac, accounting for between 30% and 35%, while mortality due to vascular, neoplastic, infection or cachexia-related causes are all roughly at the same rate, between 10% and 15%. (ABSTRACT TRUNCATED)