ADEMEX and HEMO trials: where are we going?

Free serum concentrations of the protein-bound retention solute p-cresol predict mortality in hemodialysis patients

Based on in vitro data, protein-bound uremic retention solutes have increasingly been recognized to play a pathophysiological role in the uremic syndrome. p-Cresol, a representative of this group of molecules, has been shown to be implicated in uremic immunodeficiency and endothelial dysfunction, potentially linking its serum levels to mortality. Thus far, however, no clinical information on this issue is available. To determine the relationship between p-cresol and all-cause mortality, 175 prevalent hemodialysis (HD) patients were enrolled in a prospective study. At baseline, serum levels of the water-soluble solutes urea, creatinine, and phosphate, the middle molecule beta2-microglobulin, total and free concentrations of the protein-bound solute p-cresol, and several risk factors for mortality were evaluated. During a median follow-up of 34 months, 60 patients died. Baseline comorbidity (Davies score) (hazard ratio (HR), 1.49; 95% confidence interval (95% CI), 1.19-1.86), impaired nutritional status (HR, 4.22; 95% CI, 2.15-8.29), time since initiation of dialysis (HR, 0.98; 95% CI, 0.97-1.00), and higher free concentrations of the protein-bound solute p-cresol (HR, 2.28; 95% CI, 1.12-4.64) were independently associated with mortality (multivariate Cox proportional hazards analysis). Our data suggest that free serum levels of p-cresol, a representative of the protein-bound uremic retention solutes, are associated with mortality in HD patients. These findings may encourage nephrologists to widen their field of interest beyond the scope of small water-soluble uremic solutes and middle molecules.

Standard Kt/V: Comparison of Calculation Methods

Standard Kt/V (stdKt/V) makes possible the comparison of the dialytic efficiency of different therapies, with different frequencies, whether intermittent, continuous or a mixture of both. To determine stdKt/V, the clearance of urea, a function of urea generation and blood concentration, is calculated over a period of one week and is normalized to total body water. For continuous processes, clearance per se is used. For intermittent therapy, two different equations have been developed by Gotch and by Leypoldt. Both equations allow the calculation of stdKt/V from the single-pool Kt/V (spKt/V). Gotch's method requires spKt/V and six other variables. Leypoldt's equation is simpler and limited to spKt/V plus two variables. The present study compared the nomograms created from both equations to determine their equivalence. The nomograms were superimposed for comparison. It also compared the stdKt/V obtained from random simulated patients with each method and the theoretic efficiency of continuous and intermittent clearances. The graphic comparison of the numeric values obtained appeared very similar in both methods, suggesting that either can be useful in clinical practice. A significant theoretic advantage was noted for continuous therapies over intermittent modalities. These results further support the use of frequent, daily, and continuous renal replacement therapies.

Nutrition and Metabolism in Kidney Disease

Nutritional and metabolic derangements are highly prevalent in patients with chronic kidney disease (CKD) and patients on renal replacement therapy. These derangements, which can be termed uremic malnutrition, significantly affect the high morbidity and mortality rates observed in this patient population. Uremic malnutrition clearly is related to multiple factors encountered during the predialysis stage and during chronic dialysis therapy. Several preliminary studies suggested that interventions to improve the nutritional status and metabolic status of uremic patients actually may improve the expected outcome in these patients, although their long-term efficacy is not well established. It therefore is important to emphasize that uremic malnutrition is a major comorbid condition in CKD and renal replacement therapy patients, and that all efforts should be made to try to understand better and treat these conditions effectively to improve not only mortality but also the quality of life of chronically uremic patients. In this article we review the current state of knowledge in the field of nutrition and metabolism in all stages of CKD and renal replacement therapy, including kidney transplant. We also address questions that face investigators in this field and suggest where future research might be headed.

An international registry to compare quotidian dialysis regimens with conventional thrice-weekly hemodialysis: why, how, and potential pitfalls

Thrice-weekly hemodialysis is the most commonly used form of renal replacement therapy, yet it is associated with unacceptably high morbidity and mortality. Attempts to improve outcomes for hemodialysis patients by increasing their per-session dose of dialysis have recently proven unsatisfactory in the multicentered Hemodialysis (HEMO) study. Interest has thus turned to increasing dialysis frequency. Short daily and long nocturnal dialysis, which are typically performed 6 days per week, are gaining acceptance and are associated with significant improvements in secondary outcomes, including nutrition, left ventricular hypertrophy, hypertension, anemia, and calcium-phosphorus balance. Studies to date have not been adequately powered to detect the survival benefits that these changes may confer. Large-scale randomized studies are planned, but will likely not answer the survival question for several years. Until this issue is resolved, funding policies are unlikely to change, confining current dialysis patients to potentially suboptimal therapy. By capturing data from current and future daily dialysis patients using an international registry, a survival benefit might be demonstrated more quickly. Such a project will soon be undertaken by the London Daily/Nocturnal Study Group with endorsement from the International Society for Hemodialysis and the U.S. National Institutes of Health. This database will also provide useful descriptive data that will help develop methodologies in this growing field. Historically the interpretation of dialysis registry data has been plagued with various methodological problems. These are briefly reviewed, and some potential solutions and necessary precautions are discussed.