Leptin and beta2-microglobulin kinetics with three different dialysis modalities.

BACKGROUND: Leptin is a protein produced by fat cells and involved in body weight regulation. In patients with normal kidney function, leptin has been considered an independent predictor of cardiovascular events. In uremic patients, leptin in plasma serum was assumed to be associated with malnutrition, inflammation and atherosclerosis. Because of its molecular weight and characteristics, leptin can be considered as a protein-bound uremic retention solute. Some authors have reported the possibility of decreasing the serum leptin concentration with high flux membranes, but limited data are available on the elimination with medium-flux membranes or alternative dialysis strategies such as hemodiafiltration. METHODS: We evaluated the kinetics of leptin and beta2m in a study of 18 chronic hemodialysis patients using low-flux, medium-flux and high-flux biocompatible membranes, the last one used in hemodiafiltration (HDF). Blood samples for leptin and beta2m were collected pre- and post-treatment and 30 minutes after the end of treatment, over a 1-week period that included 3 dialysis sessions. Clearances of leptin and beta2m across the dialyzer were also determined directly from the arterial and venous blood concentrations 60 and 210 minutes after starting dialysis. RESULTS: At baseline, all groups showed similar leptin (18.8+/-4.4 ng/mL) and beta2m concentrations (29.2+/-7.1 ng/mL). After a single dialysis session, a reduction of both solutes was observed with HDF (39.8+/-1.9%, 78.1+/-4.9) and medium flux membranes (18.2+/-0.9%, 52.2+/-1.7%), whereas the concentrations remained unchanged with the low-flux membranes. After one-week period, a trend of reduction of plasma pre dialysis leptin and beta2m were observed with HDF and medium flux membranes. At 60 minutes, HDF showed the best instantaneous clearance across the filter for leptin (56.2+/-10.1 ml/min) and beta2m (75.3+/-4.4 ml/min). The magnitude of post dialysis rebound of leptin at 30 min was variable and strongly correlated with the instantaneous clearance of the solute (r2= 0.88). CONCLUSIONS: Leptin serum concentration can be influenced by dialysis modalities and membrane permeability; data on rebound suggest a multicompartimental kinetic of leptin similar to beta2m. Leptin removal, as measured by the reduction rate, can be considered as an index of dialysis efficiency for protein-bound uremic retention solutes.

Evaluation of hygiene and safety controls for on-line paired hemodiafiltration (PHF).

BACKGROUND: On-line hemodiafiltration is gaining popularity due to increasing evidence of clinical benefits however it also requires strict attention to hygiene and safety as notable quantities of liquid are reinfused into the patient. Although most centers are improving their attention to water quality, a frequent concern is the inadvertent or accidental contamination of water and whether the redundant safety controls are sufficient to protect the patient. In the present study, in order to simulate a worst-case safety condition, we tested in vitro the reliability of paired hemodiafiltration - (PHF), under low, moderate and high bacterial contamination of the water supply. Tests were performed using various bacterial concentrations (range 85-2000 cfu/mL) of Pseudomonas Aeruginosa. Samples were analyzed from different sites throughout the entire on-line hemodiafiltration circuit for bacteria endotoxin, fungus and ability to stimulate whole blood production of TNFalfa. RESULTS: In the in vitro contamination study, with the three bacterial concentrations tested at various points of the circuit, bacteria were below the level of detection and endotoxins were < 0.01 UE/mL. Addition of dialysate samples taken after the first stage of microfiltration, as well as after the first and second stage of ultrafiltration and incubated with whole blood were not associated with stimulated production of TNFalfa . CONCLUSIONS: PHF appeared to be a safe and feasible method for on-line hemodiafiltration even in the unforeseen presence of bacterial contamination of the feed water or water distribution system.

How to improve dialysis adequacy in patients with vascular access problems.

Blood flow rate is a critical factor in the achievement of an adequate dialysis dose. The aim of this review is to evaluate the possibility of optimizing dialysis dose in terms of Kt/V in patients with reduced vascular access (VA) flow rate, considering effective blood flow (Qb eff), recirculation, access flow and hemodialyzer. In patients where the achievement of adequate blood flow rates are difficult to obtain and no surgical revision is necessary, to avoid under dialysis the increase in the treatment time should be the first choice solution. If such a solution is difficult for various reasons, a forced partial blood flow recirculation, especially in central venous catheters (CVCs) with reversed lines can be useful, on condition that the dialysis session is prolonged. The possibility of increasing the efficiency of dialysis through an increase in filter clearance has to be considered. Monitoring arterial pre-pump pressure (P asp) and optimizing ratio P asp/Qb eff during hemodialysis (HD) is one possible solution to improve blood flow rates, but it is necessary to educate and involve the staff. Recent developments in a new class of highly effective hemodialyzer due to dialysate distribution, has opened up interesting opportunities in terms of dialysis adequacy in patients with reduced VA flow rate.

Hemolytic uremic syndrome in adults.

The long-term clinical course of 11 adults with hemolytic-uremic syndrome (HUS) is reported. All patients were treated with heparin and antiplatelet drugs, and ten required dialysis. One patient died after 38 days; the others recovered from anuria after seven to 400 days. One patient was resubmitted to regular dialysis five years later, and another died because of cerebral hemorrhage. Among the remaining eight patients, four show renal failure and four have normal renal function after one to ten years of observation. All but three require vigorous antihypertensive therapy. It is concluded that in adults with HUS (1) recovery may occur even after a prolonged anuria; (2) severe hypertension and progressive renal failure may appear later in apparently recovered patients; and (3) heparin and antiplatelet drugs seem to be beneficial in reversing acute renal failure.

Idiopathic IgA mesangial nephropathy. Clinical and histological study of 374 patients.

Histological features and data on the natural history after 1 to 45 years (mean 6.56 +/- 8.55) of total apparent duration and 1 to 13 years (mean 3.48 +/- 5.04) of post-biopsy follow-up, are reported in 374 patients (mean age, 33.9 +/- 11.9 yrs) with idiopathic mesangial IgA nephropathy, who presented with a history of macroscopic hematuria (56%), recurrent in two-thirds of the patients, or with persistent microscopic hematuria and no previous episodes of gross hematuria (44%). Mesangial cell proliferation ranged from minimal to diffuse. Associated varying degrees of extracapillary proliferation, segmental and global glomerular sclerosis, tubulo-interstitial damage and arteriolar hyalinosis usually correlated with each other and with the extent of mesangial proliferation (P less than 0.05). The actuarial curve of progression to renal death showed a 75% survival after 20 years from apparent onset. Progression to renal failure was more rapid in patients with: an older age at onset (P = 0.0582); male sex (P = 0.0730); no history of recurrent gross hematuria (P = 0.0406); high blood pressure (P = 0.0011); more marked global (P = 0.0007) and segmental (P = 0.0026) glomerular sclerosis; more severe interstitial sclerosis (P = 0.0147); more diffuse and global mesangial proliferation (P = 0.0820); mesangio-parietal pattern at immunofluorescence (P = 0.0778). However, all these parameters showed a poor predictive value if applied to any single patient.

De novo focal glomerular sclerosis in an identical twin renal transplant recipient.

A patient with end-stage renal failure caused by bilateral kidney stones received a kidney transplant from his identical twin. No immunosuppressive therapy was given. After a few days he developed a urinary fistula from a polar artery section, which spontaneously healed. Renal function remained subnormal, blood pressure and urinalysis were normal. After one year proteinuria appeared, and after about four years it entered a nephrotic range. Renal biopsy showed focal glomerular sclerosis (FGS). In the following years progressive renal insufficiency and arterial hypertension developed, and the patient had to be submitted to regular dialysis about 9 years after transplantation. As far as we know this is the first case of late renal failure in an isograft related to the development of de novo FGS. It is suggested that de novo FGS in this isotransplant was related to the partial loss of renal mass caused by polar necrosis, which caused glomerular hyperfiltration. Another possible contributing factor may be kidney denervation, which removes an important mechanism for adjustment of renal arterial flow.

BsmI polymorphism of the vitamin D receptor gene in hyperparathyroid or hypoparathyroid dialysis patients.

Since bone mineral density may be influenced by the polymorphisms of the vitamin D receptor (VDR) gene, we studied whether VDR genotypes might drive the progression toward hyperparathyroidism or hypoparathyroidism in patients with end-stage renal disease. On the basis of their parathyroid hormone (PTH) levels, we divided 99 patients undergoing dialysis into 2 groups: 56 patients with hypoparathyroidism (PTH < 104 pg/mL [< 11 pmol/L]) and 43 with hyperparathyroidism (PTH > 261 pg/mL [> 27.5 pmol/L]). The BB polymorphism was more frequent in patients with hypoparathyroidism (34%) than in patients with hyperparathyroidism (16%), but the difference did not reach statistical significance. Patients with the B allele and BB genotype had a significantly lower dialytic age and serum PTH and alkaline phosphatase levels than patients with the b allele and bb genotype. These results suggest that in end-stage renal disease, the BB genotype may mark a higher risk of developing hypoparathyroidism and diminished bone turnover.

Gold nephropathy and renal amyloidosis in a patient with rheumatoid arthritis.

A 71-year-old Caucasian woman with rheumatoid arthritis, who had been treated with gold salts for 19 months, developed a significant proteinuria associated with nephrotic syndrome and renal impairment. Her renal biopsy revealed the unusual simultaneous occurrence of gold nephropathy and renal amyloidosis and she was treated by gold withdrawal, methylprednisolone pulses and azathioprine, with a good remission of symptoms. We describe the case and discuss the possible cause(s) of similar renal involvement and the results obtained with the combined therapy of steroids and cytotoxic drugs.

Late recovery of renal function in a woman with the hemolytic uremic syndrome.

A case is reported of the hemolytic uremic syndrome (HUS) in a woman taking oral contraceptives. She was treated with heparin, dipyridamole and hemodialysis; and after more than three months, her urinary output rose above 500 ml; and six months after the onset of anuria, dialysis treatment was stopped. This case emphasizes the possibility that HUS in adults is not invariably irreversible and that, despite prolonged oliguria, recovery of renal function can be obtained. Therefore, in adult patients affected by HUS, dialysis should not be discontinued prematurely; moreover, bilateral nephrectomy, for treatment of severe hypertension and microangiopathic hemolytic anemia, should be performed with caution.

Computerized management of peritoneal dialysis.

The importance of the evaluation of dialytic adequacy is well known in peritoneal dialysis. It is necessary to be able to quantify and individualize the substitution treatment. In 15 patients we compared five quantitative approaches by using original software: Teehan's dialysis index (DI); Diaz-Buxo's liters/week (LW); Keshaviah's the quantity of dialysis prescribed (wKt/V); and Boen and Twardowski's weekly creatinine clearance (WC). All patients were treated by continuous ambulatory peritoneal dialysis (CAPD) according to the peritoneal equilibration test (PET). Peritoneal solute clearances for urea, creatinine, uric acid, and phosphorus were adequate, but there was disagreement between adequacy indexes. According to the DI, 40% of our patients were underdialyzed, 33% were adequate, and 27% received excessive dialytic dose, while according to LW and wKt/V, about 50% were adequate, 10% underdialyzed, and 40% received excessive doses. According to WC, 74% were overdialyzed and 26% were adequate. In two patients only (13%) all the indexes indicated underdialysis. We think that the DI is too severe an adequacy index, probably because residual renal clearances have a great weight in the formula, while WC may lead to an overestimate of the actual dose of therapy in patients with significant residual renal clearance. Prospective, randomized and clinical studies are needed to better assess the optimal index for individualization of targeted peritoneal dialysis prescription.

Beta-2 microglobulin in patients on peritoneal dialysis and hemodialysis.

Serum beta 2 microglobulin (beta 2 mu) levels were determined in 62 patients on chronic dialysis, divided according to the type of dialysis--cuprophane hemodialysis, chronic ambulatory peritoneal dialysis (CAPD), or CAPD started after 76 +/- 47 months on cuprophane hemodialysis--and to residual urine output greater than 400 mL/day or less than 10 mL/day. In addition, for patients on CAPD, peritoneal excretion, peritoneal clearance, and urinary excretion of the protein were determined. In anuric patients serum beta 2 mu levels were significantly higher in HD than in CAPD. In patients with residual urine output, serum concentrations of the microprotein were similar in HD and in CAPD. Significant differences were observed in beta 2 mu serum levels and peritoneal clearances in patients switched to CAPD from hemodialysis as compared to those starting with CAPD. Peritoneal clearances of the microprotein was slightly and non-significantly greater in patients with urine output than in anuric patients.

Short-term effects of low-calcium dialysis solutions on calcium mass transfer, ionized calcium, and parathyroid hormone in CAPD patients.

Patients on CAPD using calcium carbonate (CaCO3) as phosphate binder might benefit from low-calcium (Ca) concentration dialysis solutions; however, no data are available for the effects of this regimen on Ca metabolism. We studied 10 patients on stable CAPD regimens with standard dialysis solutions (Ca 7 mg/dL) who were taking CaCO3 to control hyperphosphatemia (mean daily doses 4.5 +/- 2.4 g). Hypercalcemic episodes had been recorded in 6 patients. Standard dialysis solutions were replaced with solutions containing 5 mg/dL of Ca. Calcium and phosphate peritoneal mass transfer (MT), serum concentrations of total Ca, ionized Ca (Ca++), phosphate, intact PTH, and mid-molecular PTH, were evaluated before and 48 hours after change of dialysate. The switch to low-Ca solutions was accompanied by significant changes in calcium mass transfer (Ca MT) (+9.84 +/- 48.22 versus -96.74 +/- 48.32 mg/day, p less than .001). Ca MT was significantly (p less than .05) correlated with the serum/dialysate Ca gradient. There was no difference in phosphate MT. Serum Ca++ significantly (p less than .05) decreased from 5.20 +/- 0.32 to 4.88 +/- 0.36 mg/dL, and intact PTH significantly increased (81.5 +/- 139 versus 112.4 +/- 168 pg/mL, p less than .05). It is concluded that dialysis solutions with Ca 5 mg/dL result in a negative peritoneal Ca MT and can be useful to prevent and treat hypercalcemia in CAPD patients taking CaCO3 as phosphate binder. A careful monitoring of ionized calcium, PTH, and phosphate is suggested when an extensive and long-term use of this solution is considered.

The sigmoidal parathyroid hormone-ionized calcium curve and the set point of calcium in hemodialysis and continuous ambulatory peritoneal dialysis.

A high incidence of adynamic bone disease not related to aluminum intoxication has been reported in continuous ambulatory peritoneal dialysis (CAPD). Since reduced parathyroid hormone (PTH) secretion may predispose to adynamic bone, we investigated whether parathyroid gland sensitivity may be depressed in CAPD in comparison with hemodialysis (HD). Thus we determined parathyroid function by the evaluation of the PTH-ionized calcium (ICa) relationship, which was obtained inducing hypocalcemia and hypercalcemia in 19 CAPD and 18 HD patients with biochemical and histological evidence of mild (MILD) or severe (OF) hyperparathyroidism, but negative stainable bone aluminum. Either CAPD or HD patients with OF showed a shift to the right of the sigmoidal PTH-ICa curve in comparison with patients with MILD, greater set point of calcium, and maximal PTH stimulation and inhibition. The PTH-ICa curve and the other parathyroid function parameters were not different in CAPD and HD patients within the same bone histological group. In conclusion, our data document that parathyroid gland activity is stimulated either in CAPD and HD patients with OF, but is not depressed in CAPD patients in comparison with HD patients.

Bioelectrical impedance and hemodialysis.

Bioimpedance is a simple and non-invasive method of assessing body fluid composition. The aim of our study was to evaluate the reilability of impedance: a) to measure urea distribution volume considered to be coextensive with total body water (TBW); b) to assess the changes in body fluid compartments before and after dialysis; c) to predict hypotensive episodes. In twelve hemodialysis patients, TBW measured by bioelectrical impedance analysis (BIA) before a dialysis session was significantly correlated with the urea distribution volume estimated by dialysis direct quantification (r = 0.64, p < 0.05) and with TBW calculated by the Watson equation (r = 0.65, p < 0.05). Anthropometric values were, on average, 4.8% higher. TBW measured by BIA at the end of treatment overestimated fluid losses induced by ultrafiltration by 14% to 70%, while TBW 6 h after dialysis reflected the weight losses. On line BIA during hemodialysis has a very low positive predictive value (41.6%) and poor sensitivity (66%) for the prediction of hypotension. In conclusion, BIA is helpful in assessing the urea distribution volume but is not reliable for assessing acute fluid changes nor for predicting hypotensive episodes related to hemodialysis.

Impact of blood and dialysate flow and surface on performance of new polysulfone hemodialysis dialyzers.

Optimization of hemodialysis treatment parameters and the characteristics of the dialyzer are crucial for short- and long-term outcome of end stage renal disease patients. The new high-flux membrane Helixone in the dialyzer of the FX series (Fresenius Medical Care, Germany) has interesting features, such as the relationship of membrane thickness and capillary diameter which increases middle molecule elimination by convection, as well as higher capillary packing and microondulation to improve the dialysate flow and distribution. Blood flow, dialysate flow and surface area are the main determinants of the performance of a dialyzer, however the impact of each parameter on small and middle molecule clearance in high flux dialysis has not been well explored. In order to find the best treatment condition for the new dialyzer series, we evaluated urea, creatinine, phosphate clearances and reduction rate of beta2-microglobulin in ten stable patients treated with different blood flows (effective Qb 280 and 360 ml/min), dialysate flow (Qd 300 or 500 ml/min) and dialyzer surfaces (1.4 and 2.2 m2, FX60 or FX100). KoA and Kt/V were also calculated. Blood flow, dialysate flow and surface area demonstrated a significant and independent effect on clearance of urea, creatinine and phosphate, as well as on Kt/V. Small solute clearance was stable over the treatment. In contrast to small solutes, reduction rate of beta2-microglobulin was related to increasing dialyzer surface only. The new dialyzer design of the FX series proves highly effective due to improved dialysate distribution and reduced diffusive resistance as shown by the small solute clearance. A high reduction rate of beta2-microglobulin is favored by improved fiber geometry and pore size distribution. These findings have potential long-term benefits for the patient.

In vitro and in vivo biocompatibility of substituted cellulose and synthetic membranes.

Regenerated cellulosic membranes are held as bioincompatible due to their high complement - and leukopenia - inducing properties. Adherence of polymorphonuclear neutrophils and monocyte purified from normal human blood to the three membranes were evaluated in an in vitro recirculation circuit in the presence or absence of fresh, autologous plasma after recirculation in an in vitro circuit using minimodules with each of the three membranes. In in vivo studies, 9 patients were treated with conventional haemodialysis for 2 weeks with each membrane and 1 week for wash-out using haemodialysers with the following surface: 1.95 m2 for benzyl-cellulose, 1.8 m2 for acetate-cellulose and low-flux polysulfone. Measurement of leukopenia, plasma C3a des Arg and elastase-alpha1 proteinase inhibitor complex levels as well as urea, creatinine, phosphate and uric acid clearances was performed. Plasma-free neutrophils adhered maximally to acetate-cellulose (65% remaining in the circulation), while there was no significant difference between low-flux polysulfone and benzyl-cellulose (80% circulating neutrophils, at 15 min, p<0.001 vs acetate cellulose). In the presence of fresh plasma, as source of complement, the differences between acetate cellulose vs polysulfone and benzyl-cellulose were even more evident, suggesting the role of complement-activated products in neutrophil adherence. A similar trend was observed for monocyte adherence with the three membranes in the absence or presence of plasma. In vivo studies showed that the nadir of leukopenia was at 15 and 30 min with acetate-cellulose (79%) and benzyl-cellulose (50%) (p<0.05 acetate- vs benzyl-cellulose) and at 15 min with polysulfone (24%) (p<0.01 vs acetate- and benzyl-cellulose). Plasma C3a des Arg levels arose to 2037 +/- 120 ng/ml, 1216 + 434 ng/ml and 46 +/- 55 ng/ml with acetate-, benzyl-cellulose and polysulfone, respectively. No pre- vs post-dialysis increase in the intracellular content of TNF-alpha was detected with any of three membranes. Clearance values of urea, creatinine and uric acid were superimposable for all the three membranes. However, benzyl cellulose had a significantly higher clearance for phosphorus (normalized for surface area) (p<0.01 vs acetate-cellulose, 0.001 vs polysulfone). These results implicate that synthetic modification of the cellulose polymer as for the benzyl-cellulose significantly reduces the in vitro adherence, delays the in vivo activation of "classic" biocompatibility parameters and notably improves the removal of inorganic phosphorus.

Biochemical aspects and clinical perspectives of continuous urea monitoring in plasma ultrafiltrate. Preliminary results of a multicenter study.

We tested a new biosensor for urea monitoring in the ultrafiltrate during PFD in a group of 5 hemodialyzed stable patients. The inspection of the UF-urea profile reflects the dynamical changes of the plasma urea concentration during diffusive dialysis and allows the fitting of the main mathematical models of urea kinetics. The biosensor efficiency was 98.4% on average (SD: 1.5%) at Uf fluxes varying from 45 to 55 ml/min (mean: 51 ml/min; SD: 3.2) and at Uf-urea concentrations varying from 23 to 165 mg/dl. The mean difference between Uf-urea determined by the laboratory method and Uf-urea assayed by the biosensor was -1.07 mg/dl and the 95% confidence interval ranged from -2.01 to 0.13 mg/dl. The mean difference between laboratory plasma urea and Uf-urea from the biosensor was on average -1.9 mg/dl and the estimated limits of agreement with a confidence of 95% were -3.16 and 0.64 mg/dl. Comparison between kinetic models and experimental profiles of plasma urea decrease, evaluations of recirculation and post-dialytic rebound, the role of Kt/V on-line during dialysis were the preliminary clinical applications of this biosensor.

Effect of CAPD and hemodialysis on parathyroid function.

UNLABELLED: A high incidence of low turnover bone disease (LTBD) has been reported in predialysis and dialysis uremic patients, despite parathyroid hormone (PTH) levels two- to four-fold the upper normal limit. The aim of this study was to evaluate the trend of PTH in uremic patients after admission to continuous ambulatory peritoneal dialysis (CAPD) or hemodialysis (HD). Thus, we evaluated 53 patients (27 CAPD and 26 HD) of 73 consecutive uremic patients starting CAPD or HD from 1992, who had at least one year follow-up on dialysis. HD and CAPD patients were comparable for age, nephropathy, and duration of uremia. All the patients had been treated with calcium carbonate (CaCO3) as the sole phosphate binder during the predialysis period. At the time of admission to dialysis PTH was > 260 pg/mL (fourfold above the upper normal limit) in 12 CAPD and 9 HD patients, between 130 and 260 pg/mL in 6 CAPD and 5 HD patients, and < 130 pg/mL in 9 CAPD and 12 HD patients. Bone biopsy, performed in 22 patients, showed LTBD in 10 of 12 patients with PTH < 130 pg/mL and high bone turnover in 8 patients with PTH > 260 pg/mL. Patients were treated with a dialysate calcium (Ca) of 1.75 mmol/L and were given CaCO3 to maintain serum phosphate < 5 mg/dL. Oral calcitriol was given if they developed hypocalcemia (< 9 mg/dL). Hypercalcemia (> 10.5 mg/dL) occurred in 13 CAPD and 17 HD patients, and was managed by discontinuation of calcitriol and reduction of dialysate Ca to 1.25-1.5 mmol/L. A significant decrease in PTH and alkaline phosphatase was observed in both groups after six and 12 months of treatment. After one year of CAPD, PTH was > 260 pg/mL in 3 patients, between 130 and 260 pg/mL in 4 (all on calcitriol), and < 130 pg/mL in 20 patients (17 on calcitriol, but only 2 mild hypercalcemic). After one year of HD, PTH was > 260 pg/mL in 3 patients, 130-260 pg/mL in 5 (all on calcitriol), and < 130 pg/mL in 18 (11 on calcitriol, 1 mild hypercalcemic). IN CONCLUSION: (1) about 40% of predialysis patients treated with CaCO3 showed PTH levels suggestive of LTBD; (2) the proportion of patients with low PTH increases after one year on CAPD or HD, even though calcemia was maintained within the normal range; (3) suppressed PTH levels are associated with calcitriol therapy rather than dialysis modality; and (4) secondary hyperparathyroidism improves in most patients after one year on CAPD or HD.

Calcium mass transfer and kinetics in CAPD using calcium-free solutions.

In 12 continuous ambulatory peritoneal dialysis (CAPD) patients we evaluated peritoneal calcium mass transfer (CaMT), serum and effluent dialysate ionized calcium (iCa) changes, and the variations of the dialysate-to-plasma (D/P) ratio for calcium throughout 6-hour dwell exchanges with zero calcium, 1.25 mmol/L calcium (1.25 Ca), and 1.75 mmol/L calcium (1.75 Ca) peritoneal solutions. The infused ionized and total calcium were, respectively, 1.28 +/- 0.04 and 1.77 +/- 0.04 mmol/L with 1.75 Ca and 0.89 +/- 0.03 and 1.28 +/- 0.04 mmol/L with 1.25 Ca solutions. During CaMT studies, the ultrafiltration rate was 250 mL on average, and serum iCa 1.24 mmol/L. Calcium was gained by the patients (+0.41 +/- 0.6 mmol/L) using standard solutions. CaMT was -0.67 +/- 0.4 mmol/L with 1.25 Ca and -2.4 +/- 0.4 mmol/L with zero Ca solutions. Throughout the exchanges the D/P ratio for iCa decreased from 0.97 +/- 0.03 at 0 minutes to an equilibrium value (at about 240 minutes) of 0.84 +/- 0.03 with 1.75 Ca solutions, while it increased from 0.75 +/- 0.04 to 0.83 +/- 0.05 with 1.25 Ca solutions. After a 6-hour exchange with zero Ca, the D/P ratio for iCa was 0.76 +/- 0.04, significantly lower than the D/P ratio for urea (0.97 +/- 0.02), creatinine (0.89 +/- 0.06), and bicarbonate (0.98 +/- 0.02). In conclusion, dialysate and serum iCa are in equilibrium at a D/P ratio of about 0.84. Thus calcium is gained by the patients using 1.75 Ca solutions, and it is lost (both by diffusion and ultrafiltration) using 1.25 Ca solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

[New dialysis therapy modalities: what role do they play in the hemodialysis patient's outcome?]. / Nuovi schemi di terapia dialitica: quale ruolo nell'"outcome" del paziente in emodialisi?

Many studies have been devoted to investigating new techniques and new dialysis strategies aimed at achieving adequate removal of "uremic toxins". Conversely, few studies focus on the effect of different dialysis techniques on long-term outcome, including large series and with adequate follow-up. Dialysis dose, membrane biocompatibility and permeability, convective techniques, and the number and duration of dialysis sessions have all been considered as potentially related to patient outcome. The available data from the literature clearly show a significant relationship between the urea kinetic model based dialysis delivered and long-term patient outcome. A significant positive correlation between survival and Kt/V up to 1.3 per session in patients treated three times a week with standard low flux cellulosic dialyzers has been shown. Many studies have shown an effect of high flux membranes on the appearance of symptoms related to dialysis amyloidosis. It is likely that such an effect is further enhanced by convective or mixed techniques. The role of these techniques in patient survival is suggested by some studies, but should be confirmed in larger series. The use of techniques suitable for ultra-pure dialysis fluids are mandatory whenever high permeability membranes are used. Treatment schedules which include long dialysis sessions or an increased number of sessions such as daily dialysis, seem to be beneficial for the control of hypertension or hyperphosphatemia. However, their role on patient survival has not yet been clearly assessed. Together with the choice of the best strategy, great attention should be paid to other factors known to be related to patient outcome, such as early patient referral, and the type and efficiency of vascular access.