[Do convective treatments significantly reduce morbidity and mortality?]

Standard hemodialysis is a far from ideal treatment for uremia since the morbidity and mortality of patients on hemodialysis are still significantly higher than those of non-hemodialyzed subjects with similar demographic characteristics. Because it has been suggested that the cause could lie in the inadequate removal of ''middle molecules'' by standard hemodialyis, two alternative treatments have been proposed: high-efficiency hemodialyis and high-flux hemodialyis. The 2002 results of the HEMO study showed that both these treatments are associated with a non-significant reduction in the relative risk of death (4% and 8%, respectively). The MPO study, which - unlike the HEMO study - enrolled only incident cases and not did not allow reuse of dialyzers, evaluated the mortality rate with high-flux and low-flux hemodialysis in a sicker population, i.e., patients with hypoalbuminemia, and showed a significant reduction in the relative risk of death especially in patients with diabetes. In an attempt to define the clinical impact of hemodiafiltration, some of the efficacy data from clinical studies are reviewed in light of a number of factors that may be related to the high mortality among hemodialysis patients. The current state of affairs suggests it is reasonable to prefer high-flux hemodialysis in sicker patients, especially diabetics. Moreover, the use of ultrapure dialysis fluid is recommended to reduce chronic inflammation and its consequences.

[Recent advances in the prevention of cardiovascular morbidity and mortality in end-stage renal disease: role of anemia, hyperparathyroidism and calcifications]

The mortality rate in patients with end-stage renal disease (ESRD) is extremely high, mainly because of the high prevalence of cardiovascular disease. In addition to traditional cardiovascular risk factors, other factors peculiar to chronic kidney disease play a role. Anemia and calcium-phosphate disorders are of particular interest, not only because they have been related to an increased risk of death but, more importantly, because they can be reversed by treatment, thereby providing the opportunity to prevent or delay the onset of cardiovascular disease. Despite a clear association between higher hemoglobin levels and better survival, data from interventional trials do not seem to show a significant positive effect of hemoglobin normalization with erythropoiesis-stimulating agents on survival and left ventricular mass in ESRD patients. Nevertheless, partial correction of anemia is still an important goal to be reached, as is also suggested by international guidelines. Disorders of calcium-phosphate metabolism have also been clearly related to increased mortality. Unlike anemia, which can be easily corrected by treatment in most cases, mineral metabolism is much less effectively treated. New agents, such as phosphate binders not containing calcium and aluminum, vitamin D analogs with lower calcemic activity, and calcimimetics, are becoming increasingly available in everyday clinical practice and are likely to allow a higher percentage of patients to achieve the recommended targets for calcium-phosphate and parathyroid hormone. Given that these molecules have only been introduced recently, clear data from interventional studies showing improved survival after adequate correction of mineral metabolism parameters are still lacking.

[DOPPS estimate of guideline impact on survival in hemodialysis in Italy]

Knowing the relative risk (RR) of mortality associated with being outside the guideline targets and the percentage of patients in this situation, it is possible to estimate the number of patient life years that could be gained from adhering to guideline recommendations. We used a prevalent cross-sectional sample of 576 Italian patients from the Dialysis Outcomes and Practices Patterns Study (DOPPS) phase II (2002-2004) to determine the percentage of patients who failed to meet the Italian Society of Nephrology's targets for dialysis dose (spKt/V ≥ 1.3), anemia management (hemoglobin ≥ 11 g/dL), and mineral metabolism (serum calcium and phosphorus: ≤ 2.6 and ≤ 1.8 mmol/L, respectively), and the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (K/DOQI) targets for nutritional status (serum albumin ≥ 4 g/dL) and vascular access (facility catheter use ≤ 10%). We used a larger random sample of DOPPS patients to establish the adjusted RRs of mortality associated with the 6 examined targets. The percentage of patients outside the targets and the adjusted RRs were 34% and 1.12 for dialysis dose, 37.7% and 1.20 for anemia management, 40.8% and 1.14 for phosphorus, 14.4% and 1.22 for calcium, 62.5% and 1.46 for albumin, and 40.1% and 1.20 for facility catheter use. The adjusted sum of life years potentially gained by complete adherence to all 6 guidelines was 25,156 over a period of 5 years (2006-2010); a more conservative estimate, modeling life years potentially gained by bringing half of all patients outside targets within them, was 13,382. In conclusion, this analysis suggests opportunities to improve hemodialysis patient care in Italy. The magnitude of potential savings in life years should encourage greater adherence to guidelines and practices that are significantly associated with better survival.

[Maintenance and monitoring of water treatment system]

Water treatment systems must be submitted to maintenance, disinfections and monitoring periodically. The aim of this review is to analyze how these processes must complement each other in order to preserve the efficiency of the system and optimize the dialysis fluid quality. The correct working of the preparatory process (pre-treatment) and the final phase of depuration (reverse osmosis) of the system need a periodic preventive maintenance and the regular substitution of worn or exhausted components (i.e. the salt of softeners' brine tank, cartridge filters, activated carbon of carbon tanks) by a competent and trained staff. The membranes of reverse osmosis and the water distribution system, including dialysis machine connections, should be submitted to dis-infections at least monthly. For this purpose it is possible to use chemical and physical agents according to manufacturer' recommendations. Each dialysis unit should predispose a monitoring program designed to check the effectiveness of technical working, maintenance and disinfections and the achievement of chemical and microbiological standards taken as a reference. Generally, the correct composition of purified water is monitored by continuous measuring of conductivity, controlling bacteriological cultures and endotoxin levels (monthly) and checking water contaminants (every 6-12 months). During pre-treatment, water hardness (after softeners) and total chlorine (after chlorine tank) should be checked periodically. Recently the Italian Society of Nephrology has developed clinical guidelines for water and dialysis solutions aimed at suggesting rational procedures for production and monitoring of dialysis fluids. It is hopeful that the application of these guidelines will lead to a positive cultural change and to an improvement in dialysis fluid quality.

[The Dialysis Outcomes and Practice Patterns Study (DOPPS): results of the Italian cohort]

BACKGROUND

The Dialysis Outcomes and Practice Patterns Study (DOPPS) is an international prospective, longitudinal, observational study examining the relationship between dialysis unit practices and outcomes for hemodialysis (HD) patients in seven developed countries France, Germany, Italy, Spain, United Kingdom, Japan and the United States. Results of the DOPPS in Italy are the subject of this report.

METHODS

A national representative sample of 20 dialysis units (21 in Germany) was randomly selected in each of the European DOPPS countries (Euro-DOPPS). In these units, the HD in-center patients were included on a facility census, and their survival rates continuously monitored. A representative sample of incident (269 in Italy, 1553 in the Euro-DOPPS) and prevalent (600 in Italy, 3038 in the Euro-DOPPS) patients was randomly selected from the census for more detailed longitudinal investigation with regard to medical history, laboratory values and hospital admission.

RESULTS

Comparing the Italian and Euro-DOPPS cohorts we found comparable mean age for prevalent patients (61.4 vs. 59.5 yrs), but incident patients were older in Italy. Italian prevalent patients had less cardiovascular disease, more satisfactory nutritional status and more frequent use of native vascular access. These data were associated with a comparable mortality (15.7 vs. 16.3 deaths/100 patient yrs), but morbidity was lower in Italy. Kt/V levels were comparable in the two cohorts (1.32 vs. 1.37), but 35% of Italian patients showed a Kt/V below the recommended target. Moreover, hemoglobin levels were below 11 g/dL in 60% of Italian patients.

CONCLUSIONS

The DOPPS results bring to light several positive aspects and the opportunity for further possible improvements for Italian patients, but at the same time highlight some critical points that could represent a risk for dialysis quality.

[Guidelines on water and solutions for dialysis. Italian Society of Nephrology]

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

[Water quality cuts down the chronic inflammatory risk: how to obtain it and keep it over time]

BACKGROUND

Every week, approximately 400 liters of water used for dialysate production come into direct contact, through the semi-permeable membrane of the dialyzer, with the dialysis patient's blood stream. Therefore, submitting municipal water to an adequate depuration process before its use for dialysis becomes necessary.

METHODS

Problems related to the implementation, updating and management of a dialysis water treatment system are analyzed. The results of the most recent multicenter studies on dialysis fluids quality are also reviewed.

RESULTS

The best approach to plan, implement and manage a dialysis water treatment system, first, consists of defining the standards of chemical and microbiological water quality. The most diffused and commonly accepted standards are those recommended by the Association for Advancement of Medical Instrumentation (AAMI) and the European Pharmacopea (EP), which allow a maximum bacterial growth of, respectively, 200 CFU/ml and 100 CFU/mL and a maximum endotoxin concentration of 2 IU/mL and 0.25 IU/mL. A modern dialysis water treatment system provides a final purification process, mainly by reverse osmosis (RO), together with different pre-treatment levels and a hydraulic distribution circuit. Therefore, as RO produces water of optimal chemical and microbial quality, all efforts in the dialysis unit must be aimed at keeping this quality as constant as possible over time, by carrying out effective maintenance strategies and system disinfection. Nevertheless, several multicenter studies reported that 7-35% of water samples exceed a bacterial growth of 200 CFU/mL and that 44% of them display endotoxin concentrations >5 IU/mL.

CONCLUSIONS

The results of multicenter studies indicate that the microbial quality of dialysis fluids is, unfortunately, still an often neglected problem. Evidence of a possible relationship between dialysis fluid contamination and patient morbidity, as well as the availability of systems and machines allowing purity levels that were unimaginable only a few years ago, must be a stimulus for modifying clinical practices and starting the improvement processes aimed at maximally reducing the risk of microbial contamination in the dialysis water, as already done with chemical contamination.

[Clinical dialysis: new problems and new prospects]

The main problem nephrologists have to face today is the very high patient morbidity and mortality. A number of traditional and non-traditional risk factors have a role; among these anaemia, hypertension, dislipidemia, abnormalities in calcium-phosphate metabolism, hyperhomocysteinemia and endothelial dysfunction. An important innovation in the field of hemodialysis has been the availability of high-permeable and high-flux membranes, characterized by a high biocompatibility and ultrafiltration coefficient. The development of automatic systems to control ultrafiltration has enabled the utilisation of these membranes in the clinical setting (high-flux hemodialysis, hemofiltration, hemodiafiltration). It is common opinion that high-flux membranes can positively influence cardiovascular instability, but this has not been confirmed by clinical trials. Although preliminary data indicated a favorable effect on the correction of anemia in patients treated with high-permeable membranes, randomized trials have not shown a significant effect. Better control of anemia could be possible by means of on-line treatments, given their higher removal of medium- and large molecules and reduced microbiological and pyrogenic contamination of the dialysate. A number of analyses showed a lower incidence of bone cysts and/or carpal tunnel syndrome in patients treated with high-flux membranes compared to low-flux ones. High-flux treatments could reduce morbidity and mortality in hemodialysis patients. However, despite its large sample size, the HEMO Study has not been capable of showing a statistically significant effect of higher dialysis dose and high-flux membranes on survival and morbidity. The MPO study has been expressively designed to do a prospective evaluation of the long-term effect of membrane permeability on clinical outcomes. These results are greatly awaited.

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.

Survival of prosthetic grafts of different materials after impairment of a native arteriovenous fistula in hemodialysis patients

In our department, hemodialysis vascular accesses with graft, are used in patients with impairment of native distal and proximal arteriovenous fistulas (AVF-E). The aim of this study was to compare the survival of grafts of different materials (PTFE vs. bovine vein) in these patients. From 1991 to 1999, we prospectively evaluated 53 patients (35 women, 18 men, age 68 +/- 11 years, on dialysis for 70 +/- 65 months). Fifty-three PTFE, 10 reinforced PTFE, and 22 bovine vein grafts were placed. We evaluated the primary patency (PP) (days between fistula placement and the last dialysis before thrombosis occurred) and the secondary patency (SP) (days between fistula placement and the last dialysis treatment before it was considered lost) by separating PTFE survival from that of bovine veins. In the same patients, we also evaluated the survival of the native arteriovenous fistulas (AVF-E) during the pregraft period. Furthermore, we evaluated 404 patients (172 women, 232 men, age 65 +/- 14 years, on dialysis for 50 +/- 53 months) in whom only AVF-E were placed during the same follow-up period. Graft and AVF-E survival were calculated according to the Kaplan-Meier method. In patients with grafts, the PP at 1 year was 17.4% for PTFE and 23.9% for bovine veins. At 12 months, the SP of bovine veins was significantly higher than that of PTFE (81,9% vs. 50%, p < 0.04). In the patients who only had AVF-E, the PP and SP was, respectively, 43% at 12 months and 52.4% at 50 months. A preliminary experience in 22 patients with a 20 month follow-up confirms better survival of bovine veins than PTFE (p < 0.04).

Technical-economic management models in dialytic treatment: an evolving reality. The Italian experience

Health care organisations and financial factors (particularly treatment reimbursement rates) may influence the management of ESRD. We analysed the organisation of renal replacement therapy (RRT) in Italy, focusing on RRT population trends, patient distribution by treatment modality and provision, reimbursement rates, accreditation and quality control. Data from the Italian Dialysis and Transplant Registry and market research studies indicate that Italy has one of the highest dialysis and treatment acceptance rates in Europe. There is a high rate of hemodialysis (HD) and good use of peritoneal dialysis (PD), whereas the prevalence of transplanted patients is lower than the European mean. Dialytic treatment in private centers is limited by law to HD (mainly in Central-Southern Italy) and covers nearly 25-30% of the demand for RRT which means that, although Italy has a public national health care system, the provision of RRT is based on a "mixed" model. Regions with a higher prevalence of "private" dialysis have more dialysis centers, but a lower prevalence of PD since it is not permitted in private facilities, and fewer transplanted patients. The "public" system is not an automatic guarantee of quality and efficacy, and the "private" system is not necessarily a synonym of poor quality treatment due to its need to make a profit. The coexistence of private and public facilities (if well balanced and integrated) may in fact help overcoming bureaucracy in the public administration in relation to the demand for innovation and improving performances by means of fair competition.

Antiphospholipid (aPL) antibodies in end-stage renal disease

Data are few and conflicting about the prevalence and risk factors for antiphospholipid (aPL) antibodies in end-stage renal disease (ESRD). We studied the prevalence, risk factors and clinical manifestations of lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) among ESRD patients (chronic hemodialysis (HD) patients and kidney transplant recipients) and blood donors. LA was assessed in a large cohort (n=180) of patients by the activated partial thromboplastin time (aPTT), dilute Russel's viper venom test (dRVVT) and lupus anticoagulant-sensitive aPTT reagent (PTT-LA). IgM- and IgG-aCL were measured by a solid-phase enzyme-linked immunosorbent assay (ELISA) in 111 patients (61.5%). The prevalence of aPL was low but, it was higher in ESRD than blood donors (8.8% (16/180) vs. 0%, P=0.005); the frequency of aCL was also higher in ESRD than controls (10.8% (12/111) vs. 0%, P=0.002). LA was similar in the study and control groups (2.2% (4/180) vs. 0%, NS). Among HD patients and kidney allograft recipients there was no difference in LA (3.9% (4/101) vs. 0% (0/79), NS) and aCL frequency (18.6% (8/43) vs. 5.9% (4/68), NS). aPL was not associated with sex, age, time on HD, post-transplantation follow-up, ESRD etiology, thrombotic or hemorrhagic events, or type of HD membrane; however, these findings must be interpreted with caution, given the low frequency of aPL. In one HD patient LA activity was associated with multiple thrombosis of the access graft and native veins. In summary, the prevalence of aPL in ESRD is low but nevertheless higher than controls; LA does not appear to be related to membrane bio-incompatibility and it may be linked to vascular thrombosis; the lack of concordance between LA and aCL was apparent. Further studies are needed to clarify the issue of aPL in ESRD. LA testing should be incorporated into the diagnostic evaluation of recurrent thrombotic episodes in patients on HD.

Electrolyte disorders and substitution fluid in continuous renal replacement therapy

Electrolyte balances during acute renal failure treated with continuous convective techniques, such as continuous arteriovenous hemofiltration (CAVH) and its pumped variants, are largely dependent on the eloctrolyte plasma concentration available for ultrafiltration, the ultrafiltration rate and the composition of the replacement solution. As blood sodium concentrations measured by potentiometry (Na +P) and the total ultrafiltrate sodium concentration are very similar, Na +P can be taken as the value of ultrafilterable sodium when choosing the correct sodium concentration in the substitution fluid. In CAVH, the ultrafiltrate contains about 3 m Eq/liter of calcium and 1 m Eq/liter of magnesium that must be replaced by the substitution fluid in order to prevent hypocalcemia and hypomagnesemia. In addition, if plasma potassium levels are normal, 3 to 4 mEq/liter of potassium should be added to the replacement fluid to avoid hypokalemia. Although convection and diffusion are combined in continuous hemodialysis, solute transport is largely mediated by convection; however, the net removal of sodium and calcium is significantly influenced by their concentrations in the dialysate, and the risk of hypomagnesemia and hypokalemia can be attenuated by adjusting magnesium and potassium concentrations in the dialysis solution to levels near to the plasma water values. Since critically ill patients are prone to developing dialysis-induced hypophosphatemia, phosphorous must be monitored and supplemented if necessary, Since CRRT works continuously, serious derangement in fluid and electrolyte homeostasis may occur in the absence of careful prescription and extremely vigilant monitoring.

'Pulse oral' versus intravenous calcitriol therapy in chronic hemodialysis patients. A prospective and randomized study

The aim of this prospective and randomized study was to compare the efficacy, side effects, and costs of 'pulse oral' versus intravenous calcitriol in the treatment of secondary hyperparathyroidism in hemodialysis (HD) patients. A total of 20 patients were randomized to receive over a 4-month period pulse orally administered calcitriol (pulse oral group; n = 10) or intravenous calcitriol (intravenous group; n = 10). All patients used standard dialysate calcium (1.75 mmol/l) throughout the study period. In accordance with the study design calcium dialysate concentrations were reduced when this was necessary to avoid hypercalcemic crises. The patients were stratified into two subgroups according to their initial serum PTH levels: patients with mild or moderate degree of hyperparathyroidism (17 patients) and patients with severe hyperparathyroidism (3 patients). Intravenous and pulse oral cacitriol did not significantly reduce serum PTH concentrations in patients with severe hyperparathyroidism (1,157 +/- 156 vs. 807 +/- 228 pg/ml [corrected], p = 0.09). Intermittent calcitriol, administered by intravenous or oral route, significantly reduced serum PTH levels (326 +/- 119 vs. 109 +/- 79 pg/ml [corrected], p = 0.0001) in patients with mild or moderate hyperparathyroidism. In patients with mild or moderate hyperparathyroidism, intravenous calcitriol significantly reduced PTH concentrations at the end of the 1st month, before the increase of serum ionized calcium levels, whereas 'pulse oral' calcitriol significantly suppressed parathyroid activity at the end of the 2nd month. Calcium dialysate concentration was reduced in 9 out of 10 (90%) patients of the pulse oral group and in all patients (10/10) of intravenous group. The incidence of hypercalcemic crises was 24% (39/160) in the pulse oral group and 14% (27/160) in the intravenous group. Analysis of costs showed that intravenous calcitriol was more expensive compared to pulse oral calcitriol. These data indicate that intermittent intensive calcitriol therapy, regardless of the route of administration, is effective in suppressing parathyroid activity in HD patients with mild or moderate hyperparathyroidism. In contrast, intermittent calcitriol therapy has a limited ability to achieve sustained serum PTH reductions in HD patients with severe hyperparathyroidism. Intravenous calcitriol was more expensive than pulse oral calcitriol, and we recommend the use of pulse oral calcitriol in HD patients with mild or moderate secondary hyperparathyroidism.

Optimization of sodium removal in paired filtration dialysis by single pool sodium and conductivity kinetic models

Sodium removal is one of the main factors affecting intradialytic cardiovascular stability and interdialytic hypertension, and its removal should therefore be individualized. The aims of this study were: (1) to test the ability of a single-pool variable volume (SPVV) sodium kinetic model (NaKM) to optimize sodium removal in paired filtration dialysis (PFD), and (2) to test a SPVV conductivity kinetic model (CKM) in order to verify whether CKM can be used as an alternative for NaKM in estimating sodium balance. The mean difference between the NaKM-predicted and measured end-PFD plasma water ionized sodium concentrations was 0.00 +/- 0.55 mEq/l, which means that the model has an imprecision of < or = 1.1 mEq/ l. The mean difference between predicted and measured sodium removal was 0.21 +/- 16.86 mEq/session, which means a model overestimate of 0.21 mEq/session. The mean difference between the CKM-predicted and measured end-PFD ultrafiltrate conductivity was 0.01 +/- 0.05 mS/cm, which means an inaccuracy of the model of 0.01 mS/cm and an imprecision of < or = 0.1 mS/cm. The regression in the ionized sodium concentration measured in plasma or blood on the conductive values of the ultrafiltrate shows an error of < or = 2 mEq/l in the prediction of the ionized sodium concentration in blood by means of ultrafiltrate conductivity measurements. These results demonstrate that both models make it possible to obtain a level of dialytic sodium removal that is almost equivalent to interdialytic sodium loading. Moreover, given that it does not require blood sampling and the possibility of making repeated and inexpensive ultrafiltrate conductivity measurements, the CKM allows online monitoring of programmed sodium removal.

Intradialytic calcium balances with different calcium dialysate levels. Effects on cardiovascular stability and parathyroid function

It has been shown that calcium carbonate (CaCO3) is an effective phosphate binder which is less toxic than Al(OH)3. However, given that its use with standard calcium dialysate (CaD) levels may lead to hypercalcemia, a decrease in CaD levels has been proposed. The aim of the present study was to elevate the acute clinical and biochemical consequences of a lowering of CaD in HD patients. Dialysate composition was otherwise the same. (1) Blood pressure levels (BP) during short hemodialysis were measured in a group of 12 patients who underwent alternate hemodialyses with dialysate calcium of 1.75 and 1.25 mmol/l. (2) Ca2+ and PTH kinetics during short hemodialysis were studied in a group of 6 patients who were sequentially treated with 1.75 and 1.25 mmol/l CaD. The results show: (1) that cardiovascular stability in chronic HD patients during short HD sessions with low CaD (LCaD) may be good; (2) that a single treatment with standard CaD (SCaD) produces positive calcium balances (JCa2+) with Ca2+ plasma increase and PTHi inhibition at the end of HD sessions; during HD with LCaD there were neutral mean JCa2+ and no changes in post-dialysis mean Ca2+ and PTHi plasma levels; furthermore 2 patients showed a small PTHi increase during HD with LCaD and neutral JCa2+ because of a high positive bicarbonate balance during HD. In conclusion, as with several aspects of dialysis treatment, dialysate calcium levels should also be individualized to avoid hypercalcemic crises or PTHi stimulation.

Monitoring sodium removal and delivered dialysis by conductivity

As cardiovascular stability and the delivery of the prescribed dialysis "dose" seem to be the main factors in determining the morbidity and mortality of hemodialyzer patients today, it is of paramount importance to match hydro-sodium removal with interdialytic load and to verify the delivered dialysis at each session. A specially designed Biofeedback Module (BM--COT Hospal) allows the automatic determination of plasma water conductivity and effective ionic dialysance with no need for blood samples. Using BM, we evaluated the validity of "conductivity kinetic modelling" (CKM) and the possibility that this may substitute "sodium kinetic modelling". Moreover, we evaluated the "in vivo" relationship between ionic dialysance and effective urea clearance. Our results demonstrate that: 1) CKM makes it possible to obtain programmed end-dialysis plasma water conductivity with an error of less than +/- 0.14 mS/cm, roughly equivalent to a sodium concentration of +/- 1.4 mEq/L. 2). Ionic dialysance and effective urea clearance are not equivalent but, as the interrelationship between these is known, the BM allows the routine monitoring of delivered dialysis.

Supplemented low-protein diet and once-weekly hemodialysis

The aim of this study was to evaluate the feasibility and the nutritional and depurative adequacy of the integrated diet dialysis program. The integrated diet dialysis program consists of a low-protein diet (0.4 g/kg ideal body weight/d), supplemented with essential amino acids or a mixture of essential amino acids and chetoanalogues, and once-weekly hemodialysis, tailored to maintain predialytic blood urea nitrogen levels lower than 90 mg/dL. Sixty-nine of 84 recruited patients with a mean age of 62.9 +/- (SD) 11.1 years and a baseline glomerular filtration rate of 2.54 +/- 0.94 mL/min entered the experimental phase; 15 dropped out, eight because of poor diet compliance. At 12-month follow-up, patient and technique survival were, respectively, 89% and 56%. The laboratory, anthropometric, and instrumental parameters of 28 patients with a follow-up of more than 12 months were also evaluated using repeated measures ANOVA. Mean predialytic blood urea nitrogen values were not significantly different (82 +/- 21 mg/dL v 93 +/- 26 mg/dL at baseline and after 12-month follow-up, respectively); total weekly KT/V from residual renal function plus dialysis (1.64 +/- 0.32 v 1.70 +/- 0.29; P = NS) and dialytic index according to Babb and Scribner (1.35 +/- 0.31 v 1.21 +/- 0.33) were stable. No problems were found as far as acid-base, calcium phosphate, water-electrolyte metabolism and blood pressure control are concerned. Body weight, fat free mass, fat, plasma proteins, albumin, and C3 and C4 complement factors were stable. Creatinine production (sum of metabolized plus excreted creatinine) decreased (14.3 +/- 3.2 mg/kg/d v 13.4 +/- 2.6 mg/kg/d; P < 0.05). Transferrin decreased but not significantly (221 +/- 46 mg/dL v 204 +/- 42 mg/dL; P < 0.09). Distal motor conduction velocity from the posterior tibial nerve did not improve during the study (37.8 +/- 4.9 m/s v 36.4 +/- 4.9 m/s), while distal motor conduction velocity from the median nerve worsened (50.8 +/- 4.3 m/s v 46.3 +/- 6.3 m/s; P < 0.05). In conclusion, even though the integrated diet dialysis program may be very important in the psychologically delicate phase between the conservative and the classical three-times-a-week hemodialysis programs, and may also solve some economic and dialytically related organizational problems, it arouses some concern as far as compliance and long-term nutritional and depurative adequacy are concerned. It should therefore be limited to highly motivated patients in centers with well-trained staff or where dialysis facilities are lacking.

Antibodies to hepatitis C virus (HCV) and transaminase concentration in chronic haemodialysis patients: a study with second-generation assays

We used first- and second-generation assays such as Ortho 1, Ortho 2 and 4-RIBA to define prevalence and risk factors for anti-HCV antibodies in haemodialysed patients. Forty-nine (24%) subjects were found to be anti-HCV positive. Anti-HCV positivity was related to duration of dialysis and past or current elevations of GOT and GPT; the frequency of transfused patients was greater in HCV-positive than in HCV-negative subjects; there were 31 patients (prevalence of 20%) with anti-HCV antibodies among non-transfused patients. These findings show that, tested by second-generation assays, HCV infection is detected more than twice as commonly in haemodialysis patients and may be responsible for a significant proportion of liver disease in this clinical setting. Acquisition of hepatitis C virus by dialysis patients is not only through blood transfusions but also secondary to hepatitis C virus presence within the unit itself.