[Pharmacoeconomics in hemodialysis. Role of iron in the treatment with erythropoietin]

BACKGROUND

Although its efficacy is well known, the high economic cost of erythropoietin (EPO) raises the question of pharmacoeconomics in HD. An optimal Hb level with the lowest dosage of EPO seams to be correlated to the way of administration and an adequate iron supplementation.

METHODS

The study evaluates the influence of iron supplementation on the control of EPO-related expenses.

RESULTS

A serum ferritin level higher than 50 pg/ml in hemodialysis patients on chronic EPO therapy turned out to be adequate to keep an optimal Hb level. Our data show that this value, as far as pharmacoeconomic is concerned, is highly underestimated.

CONCLUSIONS

A higher i.v. iron supplementation correlates with a significant raise of serum ferritin level and saves on EPO-related expenses up to 1 million/per patient/per year.

Urea as a marker of adequacy in hemodialysis: lesson from in vivo urea dynamics monitoring

BACKGROUND

"Dialysis dose," a concept developed by Sargent and Gotch based on urea kinetic modeling, is a useful and recognized tool that is used to quantitate and optimize a dialysis-efficacy program. However, it has been shown that oversimplification of the "dialysis adequacy" concept to the Kt/V index might lead to dramatic underdialysis and subsequent deleterious consequences on morbidity and mortality of dialysis patients. With this perspective, the determination of Kt/V must be very cautious and rely on accurate measurement of postdialysis urea concentration and its use integrated as a tool in a quality-assurance process.

METHODS

In this study, we analyzed urea dynamics by means of a blood side (ultrafiltrate) continuous online urea monitoring system interfaced with a two-pool model hosted in a microcomputer. The study was designed to provide instantaneous dialysis performances (body and dialyzer clearances, dialyzer mass transfer coefficient) and to determine the in vivo functional permeability characteristics of the patient [intercompartment urea mass transfer coefficient (Kc)]. Thirteen end-stage renal disease patients (age 54 +/- 16 years; 12 male and 1 female) were studied during nine consecutive dialysis sessions (3 weeks).

RESULTS

Urea kinetics obtained from the urea monitoring system fitted closely the urea kinetic modeling prediction, confirming the validity of the double-pool model structure. Effective in vivo urea mass transfer coefficient averaged 912 +/- 235 mL/min/1.73 m2, a value close to those reported with more invasive methods. Large variations ranging from 363 to 1249 mL/min were observed among patients, confirming very large interindividual patient permeability differences. Interestingly, the urea mass transfer coefficient was inversely correlated with the postdialysis rebound values. Intraindividual variations were also noted as a function of time denoting functional changes in urea mass transfer coefficient values. The urea distribution volume was 38.1 +/- 7, 8 L (53 +/- 8% body weight). V1 referring to the extracellular volume and V2 to the intracellular volume were 9 +/- 2 L (13 +/- 2% body weight) and 29.2 +/- 6.6 L (41 +/- 1.3% body wt), respectively. The extracellular/intracellular volume ratio was 0.31 (approximately one third) and was not as usually defined by the paradigm 1/2 ratio.

CONCLUSION

Online double-pool urea kinetic modeling gave a new insight in urea kinetic modeling approach. Urea dynamics fit perfectly a double-compartment model structure. Accessible extracellular volume to hemodialysis is smaller than expected. The in vivo urea mass transfer coefficient must be considered as an individual and variable characteristic of ESRD patients that should be taken into consideration when prescribing the hemodialysis schedule.

Haemolipodialysis

Haemodialysis is associated with increased oxidant stress. This appears to be due to (1) an increased production of free radicals during haemodialysis, (2) a net reduction of many antioxidants and (3) factors intrinsic to the uremic state. These alterations can lead to cardiovascular disease and many of the pathologies associated with chronic renal failure. Haemolipodialysis (HLD) is a new haemodialytic technique aimed at reducing oxidant stress and removing hydrophobic or protein bound toxins. The technique uses dialysate containing ascorbic acid (vitamin C) and polyunsaturated unilamellar liposomes containing alpha-tocopherol (vitamin E). The liposomes interact with blood components at the haemodialysis membrane without passage through the membrane. Vitamin C and vitamin E are added to the system to protect the cell and plasma components from reactive oxygen species produced from activated inflammatory cells. This technique may provide a new approach in preventing free radical-associated pathologies in chronic haemodialysis patients.

Assessment of efficiency using on-line urea kinetic modeling in hemodiafiltration

Urea kinetics has recently been re-evaluated using an on-line urea monitoring system applied to hemodiafiltration. This system allows evaluation of different components possibly responsible for the gap between prescribed and delivered dose of dialysis, such as access and cardiopulmonary recirculation, and altered dialysis parameters, such as blood flow and dialysate flow rates. Furthermore, the system allows prediction of postdialysis rebound urea concentrations. The aim of the present study was to apply the on-line urea monitoring system to assess the dialytic efficiency of double chamber hemodiafiltration in different conditions of blood-dialysate flow rates, reinfusion volumes, and dialyzer configurations (high + low flux membranes or high + high flux membranes) in 10 patients (age, 60 +/- 9 years; dry weight, 65 +/- 5 kg). There was a significantly lower Kt/V (K, dialyzer clearance; t, dialysis time; V, urea distribution volume) at equilibrium with the high + high vs high + low flux configuration, possibly because of a higher tendency toward urea compartmentalization. This difference was evident when reinfusion was performed post dilution. These studies support the concept that small molecular weight uremic toxins may be more efficiently removed using low flux membranes in a modified form of hemodiafiltration.

Effect of on-line conductivity plasma ultrafiltrate kinetic modeling on cardiovascular stability of hemodialysis patients

The aim of this multicenter, prospective, randomized cross-over study was to clarify whether on-line conductivity ultrafiltrate kinetic modeling (treatment B), as a substitute for sodium kinetic modeling, is capable of reducing intradialytic cardiovascular instability in comparison with standard treatment (treatment A), by reducing the sodium balance variability. Both treatments were performed by means of a modified hemodiafiltration technique. Treatment A was performed using fixed dialysate conductivity; treatment B made use of the dialysate conductivity derived from a conductivity kinetic model, in order to obtain an end-dialysis ultrafiltrate conductivity at each dialysis session that was equal to the mean value determined in the same patient during the four-week run-in period. Thus, during treatment B, the expected end-dialysis ultrafiltrate conductivity value of each patient should have been constant. The study was carried out according to a multicenter cross-over design of 16 weeks with two treatments (A or B), two sequences (1 = ABB and 2 = BAA), a run-in period of four weeks (period 1, treatment A), and three consecutive experimental periods of four weeks each. Analysis of variance for a cross-over design was used for the statistical analysis. Forty-nine hemodialysis patients prone to intradialytic hypotension (> 25% of sessions) were enrolled from 16 participating centers, and randomly assigned to either sequence 1 (26 patients) or sequence 2 (23 patients). Six patients dropped out and four were protocol violators, which left 39 patients selected for statistical analysis. There was no difference in the average dialysate conductivity, predialysis and end-dialysis plasma water ultrafiltrate conductivity or body weight between treatment A and treatment B. Thus, the observed mean sodium balance was not different and, as expected, only the intra-patient variability of end-dialysis ultrafiltrate conductivity (index of sodium balance variability) was reduced (21%). During treatment A, systolic blood pressure decreased by 23 mm Hg (95% confidence intervals 21 to 24 mm Hg) at the end of dialysis with respect to the pre-dialysis values. Treatment B reduced this intradialytic decrease (P = 0.001) with a maximum effect at the third hour of dialysis (4.4 mm Hg, 95% confidence intervals 1.9 to 6.9 mm Hg, 23% less than during treatment A, P 0.0005) without any period or carry-over effect (P = 0.53 and 0.08, respectively). There was no treatment effect on intradialytic diastolic blood pressure (P = 0.291). In conclusion, intradialytic cardiovascular stability was significantly improved by matching the interdialytic sodium load with intradialytic sodium removal using on-line conductivity ultrafiltrate kinetic modeling as an alternative to sodium kinetic modeling. Although highly significant, this effect was clinically not very large. By applying this conductivity kinetic model to patients with a more variable sodium intake from one session to another, a greater benefit can be expected.

Acetate-free biofiltration versus bicarbonate haemodialysis in the treatment of patients with diabetic nephropathy: a cross-over multicentric study

BACKGROUND

Morbidity and mortality rates in diabetic patients on regular dialysis treatment (RDT) are higher than in non-diabetic-subjects on RDT. Moreover, diabetic patients experience an intradialitic morbidity unacceptably higher than in patients with other causes of terminal renal failure. The aim of the present investigation was to compare standard bicarbonate haemodialysis (BHD) with acetate-free biofiltration (AFB) in a group of 41 diabetic patients stable on dialysis treatment for 25 +/- 22 months.

METHODS

Twenty-four type II and 17 type I diabetic patients, all requiring insulin therapy, were included and were followed for 1 year in a 6-month cross-over randomized study for both methods. The analysis was carried out on dialysis symptoms, interdialysis symptoms, and nutritional status, and the multivariate analysis of variance for repeated measures on the same subjects in the two techniques was used.

RESULTS

AFB significantly reduced dialytic and extradialytic symptoms (P=0.003 and 0.001 respectively). Cardiovascular collapses decreased by 43%, and other dialysis symptoms showed a similar trend (-35%). The interdialysis symptoms decreased by 28% and were accompanied by an increase in subjective wellbeing (39%) when patients were switched from traditional haemodialysis to AFB. Acid base control was better with AFB (P=0.01), both at the beginning and during the session. Slightly significant differences were also obtained for Kt/V (AFB 1.48 +/- 0.29 vs BHD 1.38 +/- 0.30), while no significant difference was noted with respect to sodium mass balance, nutritional status, calorie-protein intake, nPCR, blood glucose profile, and insulin requirements. The number of hospital admissions and the mortality rate, which were much lower during the AFB than the BHD period, were not analysed statistically.

CONCLUSIONS

AFB allows better control of some metabolic aspects, reduces intra- and extradialysis symptoms, and improves patient quality of life. Whether the long-term prognosis can be improved by AFB remains to be established with further studies.

[The lipid model in hemodialyzed patients]

In the context of metabolic alteration in dialysis patients the Authors have studied the characteristics, incidence, pathogenesis, effect of dialysis, atherogenic risk and therapeutic approach to hyperlipemia in hemodialysis patients. Hypertriglyceridemia secondary to reduced lipolytic activity is the most frequent alteration observed in hemodialytic patients (36.7% of cases). In addition, hemodialysis reduces the levels of lipoprotein in the blood whereas the atherogenic role of hyperlipemia does not appear to be as important as that of arterial hypertension and smoking. Simvastatin breaks down the lipidic fractions which are involved in atherogenesis and coronary cardiopathy, thus acting as a valuable prevention against cardiovascular involvement in dialysis.

[The intradialytic kinetics of uremic toxins in the diffusion-convection hemodialysis method]

A kinetic evaluation of dialytic methods using a diffusive-convective mechanism in comparison to the standard bicarbonate dialysis was performed in order to verify the possible therapeutic uses. The "kinetic" comparison of PFD and HDF to HBD, using equal quantities of dialysate, showed no significant change in the mention of uremic toxins of small molecular weight and a more efficient capacity to extract beta 2M by the diffusive-convective methods. The biophysical evaluation of dialysis still appears to represent the best means of defining the clearance possibilities and of identifying the most suitable technique for achieving a dialytic adequacy.