Division of Nephrology, Dialysis and Renal Transplantation, ASST GOM Niguarda, Milan, Italy.
Ambrosiana Clinic-Sacra Famiglia Foundation, Milan, Italy.
PLoS One. 2020 May 29;15(5):e0233331. doi: 10.1371/journal.pone.0233331. eCollection 2020.
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.
透析尿素清除指标可能无法转化为非尿素溶质的比例清除效率。我们表明，Kt 因子（任何溶质完全从血浆体积中清除）区分了不同技术中非尿素溶质的清除效率，并且可以通过即时血液-透析液采集轻松计算。我们通过在 4 例低通量和 3 例高通量血液透析、2 例高容量血液透析后滤过和 7 例 NxStage-One 系统短时间每日透析中进行整个透析液采集，对尿素、肌酐、磷和β2-微球蛋白进行质量平衡。我们还在不同时间进行即时透析液/血液测定，并将 Kt 计算为 D/P 比值乘以输送透析液的体积加上 UF。在不同的方法之间，单次治疗和每周 Kt（整个透析液和即时计算）之间存在显著差异，最显著的是肌酐、磷和β2-微球蛋白。平衡研究中测量的尿素 Kt 几乎与基于常用血浆动力学模型的 Daugirdas 方程（eKt/V）和独立 V 计算得出的尿素 Kt 相等（eKt/V），表明完全对应。非尿素溶质 Kt 与尿素 Kt 的比值（即相对于尿素的相对清除分数）在技术之间存在显著差异，表明非尿素溶质和尿素的非比例清除。即时 Kt 高于全平衡时的 Kt，这是由于动脉和全身血液之间的浓度不平衡，但测量和计算的定量溶质清除相等，技术之间的定性 Kt 比较也相等。因此，我们表明，如 Kt 所示，尿素指标可能无法可靠地表达非尿素溶质的清除效率。Kt 可以轻松测量，而无需进行整个透析液采集，这使得可以将透析效率的指标扩展到几乎任何通过透析去除的非尿素溶质。
