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Effect of dialysis membranes and middle molecule removal on chronic hemodialysis patient survival
J K Leypoldt1, A K Cheung, C E Carroll
1Research Service, Salt Lake City Veterans Affairs Medical Center, and University of Utah, USA. ken.leypoldt@hsc.utah.edu
Abstract:
The type of dialysis membrane used for routine therapy has been recently shown to correlate with the survival of chronic hemodialysis patients. We examined whether this effect of dialysis membrane could be explained by differences in dialyzer removal of middle molecules using data from the 1991 Case Mix Adequacy Study of the United States Renal Data System. The sample analyzed included patients who had been treated by hemodialysis for 1 year or more, who were dialyzed with the 19 most commonly used dialyzers in 1991, and for whom delivered urea Kt/V could be calculated from predialysis and postdialysis blood urea nitrogen concentrations. Vitamin B12 (1,355 daltons) was used as a marker for middle molecules, and the clearance of vitamin B12 was estimated based on in vitro data. After adjustments for case mix, comorbidities, and urea Kt/V, the relative risk of mortality for a 10% higher calculated total cleared volume of vitamin B12 was 0.953 (P < 0.0001 v 1.000). Similar results were obtained when middle molecule removal was adjusted for body size. We conclude that both small and middle molecule removal indices appear to be independently associated with the risk of mortality in chronic hemodialysis patients. Differences in mortality when using different types of dialysis membrane may be explained by differences in middle molecule removal.
Insights
Dialysis membrane type impacts chronic hemodialysis patient survival. Enhanced middle molecule removal, like Vitamin B12, is linked to lower mortality risk, suggesting membrane efficiency is key.
Area of Science:
- Nephrology
- Biomedical Engineering
Background:
- Dialysis membrane type is associated with chronic hemodialysis patient survival.
- The mechanism behind this association, specifically middle molecule removal, requires further investigation.
Purpose of the Study:
- To determine if differences in middle molecule removal by various dialysis membranes explain the observed correlation with patient survival.
- To assess the independent association of small and middle molecule removal with mortality risk in chronic hemodialysis patients.
Main Methods:
- Analysis of data from the 1991 US Renal Data System Case Mix Adequacy Study.
- Inclusion of patients on hemodialysis for >= 1 year using 19 common dialyzers in 1991.
- Estimation of Vitamin B12 (a middle molecule marker) clearance using in vitro data, adjusted for urea Kt/V, case mix, and comorbidities.
Main Results:
- A 10% increase in calculated total cleared volume of Vitamin B12 was associated with a 4.7% relative decrease in mortality risk (RR=0.953, P < 0.0001).
- Similar results were observed when middle molecule removal was adjusted for body size.
- Both small and middle molecule removal indices showed independent associations with mortality risk.
Conclusions:
- Differences in mortality rates among chronic hemodialysis patients using various dialysis membranes may be attributed to variations in middle molecule removal efficiency.
- Optimizing middle molecule clearance through dialysis membrane selection is a potential strategy to improve patient survival.