Survival and factors predicting mortality in hemodialysis patients over 75 years old.

BACKGROUND: Patients starting dialysis treatments are increasingly elderly and with high morbidity and mortality. Survival and factors influencing mortality are discussed. METHODS: We studied 2,601 patients who started hemodialysis in Andalucía (Spain) between 2004 and 2007. Of these, 71 patients died in the first 90 days of hemodialysis treatment and were excluded. Three groups were considered: group A, 694 patients aged less than 60 years; group B, 1,203 patients between 60 and 75 years; and group C, 704 patients aged over 75. Survival and factors associated with mortality were studied. RESULTS: Mean survival was 46 months in group A, 41.6 in group B and 35 in the very elderly group. In univariate analysis using the Cox proportional hazards model, survival in the very elderly patients was significantly influenced by low body mass index (BMI), venous catheter as initial vascular access, arterial hypertension, congestive heart failure (CHF), late referral to nephrologist (<6 months), C-reactive protein (CRP) >10 mg/dL, serum albumin <3.5 g/dL, Kt/V (Daugirdas) <1.2 and time of dialysis session <180 minutes. In multivariate analysis, BMI, CHF, CRP, low serum albumin, Kt/V and time of dialysis session remained as independent predictors of mortality. CONCLUSIONS: Survival of the very elderly patients who remained on hemodialysis more than 90 consecutive days was poor (about 3 years). Heart failure and malnutrition/inflammation are prognostic factors related to mortality in these patients on chronic hemodialysis.

Double target comparison of blood-side methods for measuring the hemodialysis dose.

BACKGROUND: Despite the fact that urea kinetic modelling has been successfully applied to quantify the hemodialysis since the beginning of the 1980s, there is not a consensus yet concerning which is the most proper dialysis dose index and the method for calculating it. In this work, we propose that a combined measurement of the dialysis dose from two complementary perspectives of the removal process should provide a more complete description of dialysis than a measurement alone. This hypothesis is reviewed and the measuring methods are compared. METHODS: A cross-sectional randomized clinical study over 98 stable ESRD patients submitted to thrice-weekly hemodialysis was carried out with the aim of comparing 16 blood-side methods for measuring the hemodialysis dose from patient and dialyzer perspectives. The availability of urea rebound measurements and computational resources have been taken into account. RESULTS: The outcomes point to four novel blood-side methods as the most accurate for measuring the effective dialysis system Kt/V (mKt/V) in clinical conditions. Their limits of agreement (mean +/- 2.SD) range from 1.93 +/- 2.09% for a non-iterative method without the urea rebound measurement (BUN3) to -0.08 +/- 0.58% for an iterative method with BUN3. The best non-iterative blood-side method for measuring the equilibrated Kt/V (eKt/V) is the second generation formula of Daugirdas (-2.42 +/- 1.05%) when BUN3 is available and the rate equation of Daugirdas and Schneditz (-1.74 +/- 7.91%) when BUN3 is not available. The difference mKt/V-eKt/V is significant and positive, and increases with the dialysis dose in a personalized manner. CONCLUSION: We have confirmed the arguments that support the hypothesis of the study. The best blood-side methods for the combined measurement of dialysis dose as a function of the available resources have been determined.

Improving hollow fiber dialyzer efficiency with a recirculating dialysate system II: comparison against two-chamber dialysis systems.

The theoretical basis of the nonregenerated recirculating dialysate system (RDS) was derived in Part I of this work [M. Prado, L. M. Roa, A. Palma, and J. A. Milán, Ann. Biomed. Eng. (2005)]. This system pursues the maximization of the clearance of hollow fiber dialyzers whose performance is controlled by diffusion, as occurred in standard hemodialysis. In this second part we perform a comparison by digital simulation of the RDS against three well-known two-chamber dialysis systems. As a major outcome, the efficiency of the RDS increased by a factor of five-eight with respect to the efficiency of a single dialyzer operating with a number of transfer units equal to 0.1, that is when the diffusive mass-transfer of the dialyzer is exhausted. Present low-flux dialyzers do not take advantage of the full potential of this technique, but the functional domain where high-flux and high-area dialyzers operate could be more suitable to exploit this technique. We conclude that RDS can be a competitive efficient technique for optimizing the dialysis efficiency.

Improving hollow fiber dialyzer efficiency with a recirculating dialysate system. I: Theory and applicability.

The mathematical theory that underlies a novel non-regenerated recirculating dialysate system (RDS) for improving diffusive clearance in hemodialyzers is presented. The theory states the conditions that hemodialyzers must meet to be suitable in RDS optimization. We have verified the applicability of the RDS for several Cuprophan and polysulfone (PS) commercial dialyzers, showing that PS (synthetic) membranes achieve the highest increments of diffusive clearance. A numerical simulation analysis over more general conditions defined by the dimensionless groups of the system demonstrated that the highest diffusive clearance improvements are achieved in dialyzers operating with a low value of the diffusive mass-transfer area/blood flow rate ratio. This study has provided the base for the assessment of the performance of the RDS as compared to several high-efficiency systems, presented in Part II of this work [M. Prado, L. M. Roa, A. Palma, and J. A. Milan, Ann. Biomed. Eng. (2004) submitted].