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Comparative Study
. 2020 May 29;15(5):e0233331.
doi: 10.1371/journal.pone.0233331. eCollection 2020.

A simple method for the calculation of dialysis Kt factor as a quantitative measure of removal efficiency of uremic retention solutes: Applicability to high-dialysate vs low-dialysate volume technologies

Giacomo Colussi  1   2 , Chiara Carla Maria Brunati  1 , Francesca Gervasi  1   3 , Alberto Montoli  1 , Denise Vergani  1 , Federica Curci  1 , Enrico Minetti  1
Affiliations
Comparative Study

A simple method for the calculation of dialysis Kt factor as a quantitative measure of removal efficiency of uremic retention solutes: Applicability to high-dialysate vs low-dialysate volume technologies

Giacomo Colussi et al. PLoS One. .

Abstract

Dialysis urea removal metrics may not translate into proportional removal efficiency of non-urea solutes. We show that the Kt factor (plasma volume totally cleared of any solutes) differentiates removal efficiency of non-urea solutes in different technologies, and can easily be calculated by instant blood-dialysate collections. We performed mass balances of urea, creatinine, phosphorus and beta2-microglobulin by whole dialysate collection in 4 low-flux and 3 high-flux hemodialysis, 2 high-volume post-hemodiafiltration and 7 short-daily dialysis with the NxStage-One system. Instant dialysate/blood determinations were also performed at different times, and Kt was calculated as the product of the D/P ratio by volume of delivered dialysate plus UF. There were significant differences in single session and weekly Kt (whole dialysate and instant calculations) between methodologies, most notably for creatinine, phosphorus and beta2-microglobulin. Urea Kt messured in balance studies was almost equal to that derived from the usual plasma kinetic model-based Daugirdas' equation (eKt/V) and independent V calculation, indicating full correspondence. Non-urea solute Kt as a fraction of urea Kt (i.e. fractional removal relative to urea) showed significant differences between technologies, indicating non-proportional removal of non-urea solutes and urea. Instant Kt was higher than that in full balances, accounting for concentration disequilibrium between arterial and systemic blood, but measured and calculated quantitative solute removal were equal, as were qualitative Kt comparisons between technologies. Thus, we show that urea metrics may not reliably express removal efficiency of non-urea solutes, as indicated by Kt. Kt can easily be measured without whole dialysate collection, allowing to expand the metrics of dialytic efficiency to almost any non-urea solute removed by dialysis.

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Conflict of interest statement

I have read the journal's policy and the authors of this manuscript have the following competing interests: Drs.GC and CCMB have been past medical advisors for NxStage Medical Inc, Lawrence, MA; Drs.CCMB and EEM received fees as speaker in dialysis industry-sponsored symposia at the National Congress of Italian Society of Nephrology. Drs. AM, FG, DV and FC have no conflict of interests to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1
Fig 1. D/P values “instant” and in full balances.
D/P ratios of urea, creatinine, phosphorus and b2M are shown as instant data at different treatment times, as mean of all intra-session values (Mean), and as corresponding values in full balance studies (Bal). For NSO, repeated instant calculations are available in a single study, and “Mean” points represents instant calculations at 60 min. Inset indicates treatment modality.
Fig 2
Fig 2. Correlation between Ktbal and Ktinst.
Individual data for urea, creatinine, phosphorus and b2M is shown. Correlation equation lines (full) and coefficients, and identity lines (interrupted) are indicated. Inset indicates treatment modality.
Fig 3
Fig 3. Correlation between measured (Qbal) and calculated (Qinst) solute quantity in spent dialysate.
Individual data for urea, creatinine, phosphorus and b2M is shown; Qbal is measured in full dialysate collection, Qinst is estimated quantity by “instant” calculations. Correlation equation lines (full) and coefficients, and identity lines (interrupted) are indicated. U indicates unit of measure (g for urea, mg for all other). Inset indicates treatment modality.
Fig 4
Fig 4. Ratio of individual non-urea solutes Kt to urea Kt in each dialytic methodology according to full balance studies (top) or instant calculations (bottom).
Individual solutes and significant differences are indicated in the graph.
See this image and copyright information in PMC

References

    1. Tattersall J, Martin-Malo A, Pedrini L, Basci A, Canaud B, Fouque D, et al. EBPG guideline on dialysis strategies. 3. Dialysis dose methodologies. Nephrol Dial Transplant 2007; 22(Suppl 2): 5–21 - PubMed
    1. Leypold JK, Weinhandl ED, Collins AJ. Volume of urea cleared as a therapy dosing guide for more frequent hemodialysis. Hemodial Int 2018; 23(1): 42–49 - PubMed
    1. Brunati C, Gervasi F, Casati C, Querques ML, Montoli A, Colussi G. Phosphate and calcium control in short frequent hemodialysis with the NxStage System One Cycler: mass balance studies and comparison with standard thrice-weekly bicarbonate dialysis. Blood Purif 2018; 45(4): 334–342. - PubMed
    1. Brunati CCM, Gervasi F, Cabibbe M, Ravera F, Menegotto A, Querques M, et al. Single Session and Weekly Beta 2-Microglobulin Removal with Different Dialytic Procedures: Comparison between High-Flux Standard Bicarbonate Hemodialysis, Post-Dilution Hemodiafiltration, Short Frequent Hemodialysis with NxStage Technology and Automated Peritoneal Dialysis. Blood Purif. 2019;48(1): 86–96 - PubMed
    1. Colton CK, Smith KA, Merrill EW, Friedman S. Diffusion of urea in flowing blood. Ann Inst Chem Eng J 1971; 17(4): 800–801

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