Preservation of residual renal function in peritoneal dialysis patients: still a dream?

The results of the randomized trial by Fan et al. suggest that 'biocompatible' peritoneal dialysis solutions have no major advantage over standard solutions in peritoneal dialysis patients in relation to residual renal function (RRF) and technique survival. The possible effect of more biocompatible peritoneal dialysis solutions on RRF should be tested in patients starting peritoneal dialysis programs with relatively well-preserved RRF. When RRF is already very poor, it is very unlikely that a more biocompatible peritoneal dialysis solution can preserve highly damaged and sclerotic kidneys.

Simultaneous measurement of peritoneal glucose and free water osmotic conductances.

Ultrafiltration (UF) failure is one of the most important causes of long-term peritoneal dialysis (PD) failure in patients. Osmotic forces acting across small and ultra-small pores generate a UF with solutes through the small pore and free water transport (FWT) through the ultra-small pore. The ability of glucose to exert an osmotic pressure sufficient to cause UF is the so-called 'osmotic conductance to glucose' (OCG) of the peritoneal membrane. Our study proposes a simple method to determine both the OCG and FWT. In 50 patients on PD, a Double Mini-Peritoneal Equilibration Test (Double Mini-PET), consisting of two Mini-PET, was performed consecutively. A solution of 1.36% glucose was used for the first test, whereas a solution of 3.86% glucose was used for the second test. The sodium removal values and the differences in UF between the two tests were used to calculate FWT and the OCG. Patients with UF failure showed significant reductions not only in the OCG and the FWT but also of UF of small pores. The Double Mini-PET is simple, fast, and could become useful to evaluate patients on PD in everyday clinical practice.

Color Doppler ultrasonography percutaneous transluminal angioplasty of vascular access grafts.

Percutaneous transluminal angioplasty (PTA) is a possible treatment for stenosis. This study aimed to verify the impact of a vascular access (VA) surveillance protocol, based on the detection of functional changes and their correction by a new PTA method for VA performed under color Doppler ultrasonography (CDU) guidance. We divided the patients into two groups: group A, before May 1999 (retrospective study) without the surveillance protocol, and group B, from 1 May 1999 to January 2001 (prospective study) with the surveillance protocol. Access blood flow (Qa) was assessed every 4 weeks by ultrasound velocity dilution. In cases of a reduction of >or=35% from the baseline value, VA was examined using CDU: if a stenosis >50% was detected, angioplasty was performed. In cases of Qa reduction <35% we continued monitoring. By Coxs multivariate analyses, only the use of PTA with or without stenting reduced the relative risk of thrombosis by 64% during the follow-up (p=0.017 confidence intervals 88%-15%) in group B patients. Secondary patency was 80% for VA in which we performed PTA with or without stenting at 18 months, and 58% at 18 months in which we did not perform PTA. Our data show how PTA under CDU is useful to maintain and to improve graft patency. This PTA under CDU guidance allows patients to avoid surgical intervention, hospitalization, and adverse reactions to contrast media and exposure to ionizing radiation, with reduced cost and with better graft survival.

[Antimicrobial agents for preventing peritonitis in peritoneal dialysis: guideline from the Italian Society of Nephrology]. / Strategie antimicrobiche per la prevenzione delle peritoniti in dialisi peritoneale: Linea Guida.

BACKGROUND: The current 3rd edition of the Italian Society of Nephrology guidelines has been drawn up to summarize evidence of key intervention issues on the basis of systematic reviews (SR) of randomized trials (RCT) or RCT data only. The present guideline reports evidence of the use of antimicrobial agents for preventing peritonitis in peritoneal dialysis (PD). METHODS: SR of RCT and RCT on treatments aiming at preventing peritoneal dialysis peritonitis were identified referring to a Cochrane Library and Renal Health Library search (2005 update). Quality of SR and RCT was assessed according to current methodological standards. RESULTS: One SR and 19 RCT were found addressing this issue. Staphylococcus Aureus nasal carriage treatment with mupirocin reduces exit-site and tunnel infections but not peritonitis. Topical gentamicin treatment on the exit site reduces Staphylococcus Aureus infection and peritonitis incidence. Intravenous antibiotics administration prior to catheter placement significantly reduces the risk of early peritonitis but not exit-site and tunnel infections. Oral nistatin associated with antibiotic treatment significantly reduces the incidence of Candida peritonitis. No other prophylaxis measure seems to be effective based on available evidence. CONCLUSION: In patients on peritoneal dialysis current evidence supports the hypothesis that topical mupirocin reduces the risk of Staphylococcus Aureus peritonitis, intravenous antibiotics prior to catheter placement prevent the risk of early peritonitis, and oral nistatin reduces the risk of Candida peritonitis. Further studies are necessary to test the effectiveness of other interventions.

[Catheter-related interventions to prevent peritonitis in peritoneal dialysis: guideline from the Italian Society of Nephrology]. / Strategie correlate al catetere per la prevenzione delle peritoniti in dialisi peritoneale: Linea Guida.

BACKGROUND: The current 3rd edition of the Italian Society of Nephrology guidelines has been drawn up to summarize evidence of key intervention issues on the basis of systematic reviews (SR) of randomized trials (RCT) or RCT data only. The present guideline report evidence of catheter-related interventions to prevent peritonitis in peritoneal dialysis (PD). METHODS: SR of RCT and RCT of catheter-related interventions to prevent peritonitis in PD were identified referring to a Cochrane Library and Renal Health Library search (2005 update). RESULTS: Two SR and 17 RCT were found addressing this issue. Methodological quality of available RCT was suboptimal according to current methodological standards. The use of the Y-set systems with disinfectant and the twin-bag systems was associated with a significantly lower risk of peritonitis. No other catheter-related interventions were found to be of proven efficacy in preventing the risk of peritonitis and exit-site/tunnel infection in PD patients. CONCLUSION: It is still unknown whether any particular PD catheter design or implantation technique are effective to prevent peritonitis in patients on peritoneal dialysis. Further studies are necessary to test the effectiveness of new interventions.

[Treating peritonitis in peritoneal dialysis: guideline from the Italian Society of Nephrology]. / Terapia iniziale della peritonite in dialisi peritoneale: Linea Guida.

BACKGROUND: The current 3rd edition of the Italian Society of Nephrology guidelines has been drawn up to summarize evidence of key intervention issues on the basis of systematic reviews (SR) of randomized trials (RCT) or RCT data only. The present guideline reports evidence of interventions to treat peritonitis in peritoneal dialysis (PD). METHODS: SR of RCT and RCT on treatments for peritoneal dialysis peritonitis were identified referring to a Cochrane Library and Renal Health Library search (2005 update). Quality of SR and RCT was assessed according to current methodological standards. RESULTS: Thirty-six RCT were found addressing the intervention issue. Vancomycin or first generation cephalosporins may be used for treating peritoneal dialysis peritonitis due to Gram-positive agents. Third-generation cephalosporins or amino-glycosides may be used for Gram-negative agents peritonitis. Association of first-generation cephalosporins and agents against Gram-negative bacteria via the intraperitoneal route represents the most frequently used approach. Intraperitoneal administration of antibiotic agents is the most effective treatment of peritoneal dialysis peritonitis. Intermittent administration may be preferred to continuous administration of antibiotic agents in peritoneal dialysis peritonitis. CONCLUSION: In peritoneal dialysis peritonitis current evidence supports the hypothesis that intraperitoneal administration of antibiotics agents and intermittent administration may be preferred to other routes of administration and continuous administration. Further studies are necessary to test this hypothesis in selected patient populations.

[Peritoneal equilibration test: actuality and future perspectives]. / Test di equilibrazione peritoneale: attualità e prospettive future.

The most widely used peritoneal function test is the peritoneal equilibration test (PET), developed and described by Twardowski in 1987. PET is performed using a 2.27% glucose solution and it lasts 4 hours. It measures peritoneal solute transport and ultrafiltration. PET gives the possibility to categorise patients (high, high-average, low-average and low transporters). However, a PET with 3.86% glucose provides better information on ultrafiltration and the phenomenon of sodium sieving provides an assessment of free water transport. Two recently developed tests (Mini-PET, Double Mini-PET) are promising tools to assess the free water transport and the osmotic conductance to glucose. The above new insights in the peritoneal function need of a new standardization of the PET. It possible that the ''new PET'' will be performed by a machine (PET-machine) in order to avoid the mistakes during the performance of manual PET and to allow an universal standardization of the test.

Peritoneal transport assessment by peritoneal equilibration test with 3.86% glucose: a long-term prospective evaluation.

The peritoneal equilibration test (PET) with 3.86% glucose concentration (3.86%-PET) has been suggested to be more useful than the standard 2.27%-PET in peritoneal dialysis (PD), but no longitudinal data for 3.86%-PET are currently available. A total of 242 3.86%-PETs were performed in 95 incident PD patients, who underwent the first test during the first year of treatment and then once a year. The classical parameters of peritoneal transport, such as peritoneal ultrafiltration (UF), D/D(0), and D/P(Creat), were analyzed. In addition, the absolute dip of dialysate sodium concentration (DeltaD(Na)), as an expression of sodium sieving, was studied. D/D(0) was stable, and a progressive decrease in UF was observed after the second PET, whereas D/P(Creat) firstly increased and then stabilized. DeltaD(Na) was the only parameter showing a progressive decrease over time. On univariate analysis, D/D(0) and DeltaD(Na) were found to be significantly associated with the risk of developing UF failure (risk ratio (RR) 0.987 (0.973-0.999), P=0.04, and RR 0.768 (0.624-0.933), P=0.007, respectively), but on multivariate analysis only DeltaD(Na) showed an independent association with the risk of developing UF failure (RR 0.797 (0.649-0.965), P=0.020). UF, D/D(0), and D/P(Creat) changed only in those patients developing UF failure, reflecting increased membrane permeability, whereas DeltaD(Na) significantly decreased in all patients. The 3.86%-PET allows a more complete study of peritoneal membrane transport than the standard 2.27%-PET. DeltaD(Na) shows a constant and significant reduction over time and is the only factor independently predicting the risk of developing UF failure in PD patients.

[Sodium kinetics in peritoneal dialysis: from theory to clinical practice]. / Cinetica del sodio in dialisi peritoneale: dalla teoria alla pratica clinica.

Cardiovascular disease (CVD) is the leading cause of death in dialysis patients. Among the main risk factors for CV mortality, hydro-saline retention is frequently observed in peritoneal dialysis (PD) patients, due to the transport mechanisms occurring within the peritoneal cavity. The analysis of sodium (Na) kinetics is a useful method to understand better the transport of fluids and solutes in PD. In the absence of peritoneal ultrafiltration (UF), Na removal by diffusion during a peritoneal dwell is extremely low. Therefore, to increase peritoneal Na removal, the attainment of peritoneal UF is a basic requisite; however, achieving this goal requires the use of solutions with hypertonic glucose concentrations. On the other hand, such a type of convective transport induces the transport of free-water, by aquaporin-1 channels located on the endothelial side of the peritoneal membrane; therefore, leading to a disproportionate removal of plasmatic water as compared with the removal of plasmatic Na (hyponatric removal). PD solutions containing icodextrin at 7.5% concentration determine UF with a different mechanism (colloid-osmotic), without inducing any free-water transport. However, clinical studies have failed to show a benefit of icodextrin solution in reducing blood pressure (BP) values and increasing Na removal. Therefore, the use of PD solutions with low Na concentrations (102-120 mmol/L) has been recently proposed as another available therapeutic strategy to prevent the development and reduce the prevalence of hydro-saline retention and hypertension in PD patients.

How to determine ionic dialysance for the online assessment of delivered dialysis dose.

BACKGROUND: Ionic dialysance may be equivalent to blood-water urea clearance corrected for recirculation (effective urea clearance); however, this is controversial. The aims of our study were (1) to verify in vivo whether the value of ionic dialysance is affected by the method of determination, given the effect of cardiopulmonary recirculation on inlet plasma water conductivity when the inlet dialysate conductivity is changed; and (2) to define the operative modalities for determining ionic dialysance to obtain an adequate estimate of effective urea clearance. METHODS: Thirty-three hemodialysis patients were studied during 186 dialysis sessions with low-flux polysulfone dialyzers using a modified Fresenius Medical Care 4008 B machine equipped with meters to measure inlet and outlet dialysate conductivities. This machine varied inlet dialysate conductivity (Cdi) according to the following pattern: starting from baseline (step 0), Cdi was increased by 8% (step 1). After Cdi had reached the target value, which took 8 to 10 minutes, it was lowered to 8% below the baseline value (step 2). After 8 to 10 minutes, when Cdi had reached the new target, it was returned to its starting value (step 3). Four values of conventional ionic dialysance (using the standard formula) and actual ionic dialysance (taking into account cardiopulmonary recirculation) were obtained for each cycle and were compared among them and with effective urea clearance (Kde). RESULTS: Mean conventional dialysance values at steps 0 to 2 and 2 to 3 (190 and 189 mL/min) were similar and higher than those at steps 0 to 1 and 1 to 2 (171 and 181 mL/min). Mean conventional ionic dialysance values underestimated Kde, particularly at steps 0 to 1 (-22.2 mL/min, P < 0.001) and 1 to 2 (-12.6 mL/min, P < 0.001). The actual dialysance values underestimated Kde by no more than 4.3 mL/min (P < 0.001). In steps 0 to 1 and 1 to 2, the underestimate of Kde by conventional dialysance increased at higher values of Kde, but this relationship did not exist when considering actual dialysance. CONCLUSIONS: The value of ionic dialysance is affected by the method of determination, given the effect of cardiopulmonary recirculation on inlet plasma water conductivity when inlet dialysate conductivity is changed. As a consequence, to provide a correct and direct estimate of effective urea clearance, ionic dialysance must be determined by changing inlet dialysate conductivity in such a way as to keep inlet plasma water conductivity constant by means of two symmetrical high and low dialysate conductivity steps.

Spurious estimations of sodium removal during CAPD when [Na](+) is measured by Na electrode methodology.

BACKGROUND: The aim of this study was to investigate the effect of pH and glucose concentration on sodium removal and the dialysate and plasma sodium ratio (D/PNa) as measured by means of a flame photometer (NaF) or direct ion-selective electrode (NaE) in continuous ambulatory peritoneal dialysis (CAPD). METHODS: In vitro, glucose concentration, pH, NaF, and NaE were measured in fresh peritoneal dialysis solutions (PDSs) before and after the addition of glucose or KOH. In vivo, 66 four-hour peritoneal equilibration tests were performed in 35 patients on CAPD using a low pH PDS with a glucose concentration of 3.86%. RESULTS: In vitro, NaF and NaE were significantly influenced by the glucose concentration and pH of the PDS. In vivo, in fresh PDS, there was a significant difference between the NaF and NaE results; the respective median values were 132.1 (interquartile range 129.3 to 137.5) versus 138.0 (134.4 to 141.5) mmol/L (P < 0.0001). The D/PNa ratio calculated by NaE was significantly lower than that calculated by NaF (0.88 +/- 0.03 vs. 0.91 +/- 0.04 and 0. 90 +/- 0.03 vs. 0.94 +/- 0.04 at 60 and 240 min, respectively, P < 0.0001), whereas there was no significant difference between the NaE and NaF values after correction for plasma water and a Donnan factor of 0.96 (0.88 +/- 0.03 vs. 0.88 +/- 0.04 and 0.90 +/- 0.03 vs. 0.91 +/- 0.04, P < 0.3473). Sodium removal was significantly lower when calculated as NaE than when calculated as NaF (43.9 +/- 32.7 vs. 61.0 +/- 32.2 mmol, P < 0.0001). CONCLUSIONS: The fresh PDS sodium concentration can be corrected using a glucose concentration-related factor. The D/PNa ratio calculated as NaE or NaF is not different after correction for plasma water and a Donnan factor of 0.96. Sodium removal must be measured by means of NaF rather than NaE. This could have an important clinical impact.

Effect of high-flux dialysis on the anaemia of haemodialysis patients.

BACKGROUND: Anaemia is one of the major clinical characteristics of patients with chronic renal failure, and has a considerable effect on morbidity and mortality. Adequate dialysis is of paramount importance in correcting anaemia by removing small and medium-sized molecules, which may inhibit erythropoiesis. However, high-molecular-weight inhibitors cleared only by means of highly porous membranes have also been found in uraemic serum and it has been claimed from uncontrolled studies that high-flux dialysis could improve anaemia in haemodialysis patients. METHODS: We therefore planned this multicentre randomized controlled trial with the aim of testing whether the use of a large-pore biocompatible membrane for a fixed 12-week follow-up improves anaemia in haemodialysis patients in comparison with the use of a conventional cellulose membrane. Eighty-four (5.3%) of a total of 1576 adult haemodialysed patients attending 13 Dialysis Units fulfilled the entry criteria and were randomly assigned to the experimental treatment (42 patients) or conventional treatment (42 patients). RESULTS: Haemoglobin levels increased non-significantly from 9.5+/-0.8 to 9.8+/-1.3 g/dl (dP=0. 069) in the population as a whole, with no significant difference between the two groups (P:=0.485). Erythropoietin therapy was given to 32/39 patients (82%) in the conventional group, and 26/35 (74%) in the experimental group (P:=0.783) with subcutaneous administration to 26/32 patients in conventional and to 23/26 patients in experimental group, P:=0.495. Dialysis dose (Kt/V) remained constant in both groups (from 1.30+/-0.17 to 1.33+/-0.20 in the conventional group and from 1.28+/-0.26 to 1.26+/-0.21 in the experimental group, P:=0.242). Median pre- and post-dialysis beta(2)-microglobulin levels remained constant in the conventional group (31.9 and 34.1 mg/dl at baseline) and decreased in the experimental group (pre-dialysis values from 31.1 to 24.7 mg/dl, P:=0.004 and post-dialysis values from 24.8 to 20.8 mg/dl, P:=0.002). Median erythropoietin doses were not different at baseline (70 IU/kg/week in conventional treatment and 90 IU/kg/week in experimental treatment, P:=0.628) and remained constant during follow-up (from 70 to 69 IU/kg/week in the conventional group and from 90 to 91 IU/kg/week in the experimental group, P:=0.410). Median erythropoietin plasma levels were in the normal range and remained constant (from 12.1 to 12.9 mU/ml in the conventional group and from 13.2 to 14.0 mU/ml in the experimental group, P:=0.550). CONCLUSIONS: This study showed no difference in haemoglobin level increase between patients treated for 3 months with a high-flux biocompatible membrane in comparison with those treated with a standard membrane. When patients are highly selected, adequately dialysed, and have no iron or vitamin depletion, the effect of a high-flux membrane is much less than might be expected from the results of uncontrolled studies.

Color doppler ultrasonography imaging to guide transluminal angioplasty of venous stenosis.

BACKGROUND: The objective of access surveillance is the early recognition of dysfunction in order to be able to correct the stenosis by angioplasty or surgery before access thrombosis occurs. The advent of color Doppler imaging has enabled studies of color Doppler ultrasonography (CDU) for the guidance of percutaneous transluminal angioplasty (PTA). The aim of the present study was to investigate whether color Doppler imaging alone can be safely and effectively used to diagnose vascular graft access stenoses and guide subsequent PTA. METHODS: Using the ultrasound velocity dilution method, we measured access blood flow (Qa) during the first hour of hemodialysis every month in patients with grafts as vascular access. When the decrease in Qa from the baseline value was 40% or more, CDU was performed and immediately followed by PTA in the presence of a stenosis of more than 50%. The Qa was then measured during the first dialysis after PTA and one month later. Repeated-measure analysis of variance was applied to evaluate the early and late (after one month) effect of PTA. RESULTS: Twelve PTAs were performed under CDU guidance in nine patients and led to the elimination of the stenosis or its reduction (two cases). The mean Qa was 809 +/- 263 mL/min at baseline, 468 +/- 153 before PTA, and 820 +/- 281 after PTA. The difference between the pre-PTA and post-PTA values was highly significant (P < 0.001), and the mean value after PTA was not different from baseline (P = 0.672). There were no relevant complications directly related to the procedure. CONCLUSIONS: The CDU procedure is effective for the diagnosis of vascular access stenosis and as a guide during the PTA procedure. It could improve stenosis screening by avoiding the risks of exposure to ionizing radiation and of adverse reactions to contrast media.