Francesco Gaetano Casino: Dialysis Centre SM2, Policoro, Italy.
Clinical Research Branch, Division of Nephrology, Miulli General Hospital, 70121, Acquaviva delle Fonti, Italy.
J Nephrol. 2021 Apr;34(2):459-464. doi: 10.1007/s40620-020-00843-9. Epub 2020 Oct 27.
The normalized protein catabolic rate (PCRn) is one of the key indices derived from the urea kinetic model (UKM) in haemodialysis (HD) patients. Ideally, it should be assessed using the double pool UKM (KDOQI clinical practice guidelines, AIKD, 2015), as the web-based software Solute-Solver (SS) does (Daugirdas et al., AJKD, 2009). Simple formulae exist to compute PCRn for patients on thrice- or twice-weekly HD schedule, but not for patients on once-weekly HD schedule (1HD/wk). Aim of the present technical note was to introduce the lacking equation that estimates PCRn in the 1HD/wk regimen.
Data of a single HD session associated to monthly UKM studies were retrieved from the electronic database of our dialysis unit for 80 historical patients on 1HD/wk regimen. The UKM parameters, as calculated with SS, were used in a subgroup of 40 randomly selected patients (group 1) to build-up a multiple regression model of PCRn. The latter was used to predict PCRn (PCRn) values in the cohort of the remaining 40 patients (group 2). The Bland-Altman plot was used to analyse the agreement between PCRn and the paired "observed" (PCRn) values, as measured with SS.
The following equation was established by means of the multiple regression analysis: PCRn = - 0.46 + 0.01 × C0 + 0.09 × eKt/V + 3.94 × Kru/V, where C0 is pre-dialysis blood urea nitrogen concentration, eKt/V is the equilibrated Kt/V, Kru is the residual renal urea clearance and V is the post-dialysis urea distribution volume. The PCRn values were 0.99 ± 0.24 g/kg/day; the PCRn values were 0.96 ± 0.23 g/kg/day (mean difference 0.03 ± 0.05 g/kg/day). Their difference at the Bland-Altman analysis ranged from - 0.08 to + 0.13 g/kg/day. Finally, a nomogram was drawn: it can be used to estimate not only PCRn from Kru/V and C0, but also C0 as a function of Kru/V and PCRn.
The equation here introduced allows a simple and accurate estimate of PCRn in patients on once-weekly HD regimen. The availability of the nomogram relating C0 to PCRn and Kru/V could be a further step to make safer and safer the once-weekly HD regimen. The following equation was established by means of the multiple regression analysis [Formula: see text] where PCRn is the normalized protein catabolic rate (PCRn), C0 is pre-dialysis blood urea nitrogen concentration (BUN), eKt/V is the equilibrated Kt/V, Kru is the residual renal urea clearance and V is the post-dialysis urea distribution volume. A nomogram relating pre-dialysis BUN to PCRn and Kru/V could be drawn: it can be used to estimate not only PCRn from Kru/V and pre-dialysis BUN, but also pre-dialysis BUN as a function of Kru/V and PCRn.
标准化蛋白分解率（PCRn）是血液透析（HD）患者从尿素动力学模型（UKM）中得出的关键指标之一。理想情况下，应该使用双池 UKM（KDOQI 临床实践指南，AIKD，2015 年）来评估它，因为基于网络的 Solute-Solver（SS）软件可以做到这一点（Daugirdas 等人，AJKD，2009 年）。有简单的公式可以计算每周三次或两次 HD 方案的患者的 PCRn，但不适用于每周一次 HD 方案（1HD/wk）的患者。本技术说明的目的是引入缺乏估计每周一次 HD 方案患者 PCRn 的方程。
从我们透析单位的电子数据库中检索了 80 名每周一次 HD 方案的历史患者单次 HD 治疗期间与每月 UKM 研究相关的数据。使用 SS 计算的 UKM 参数被用于 40 名随机选择的患者（第 1 组）的亚组中，以建立 PCRn 的多元回归模型。该模型用于预测剩余 40 名患者（第 2 组）的 PCRn 值。Bland-Altman 图用于分析 PCRn 与 SS 测量的配对“观察”（PCRn）值之间的一致性。
通过多元回归分析建立了以下方程：PCRn=-0.46+0.01×C0+0.09×eKt/V+3.94×Kru/V，其中 C0 是透析前血尿素氮浓度，eKt/V 是平衡的 Kt/V，Kru 是残余肾尿素清除率，V 是透析后尿素分布容积。PCRn 值为 0.99±0.24g/kg/天；PCRn 值为 0.96±0.23g/kg/天（平均差值 0.03±0.05g/kg/天）。在 Bland-Altman 分析中，它们的差值范围为-0.08 至+0.13g/kg/天。最后，绘制了一个诺模图：它不仅可以根据 Kru/V 和 C0 来估计 PCRn，还可以根据 Kru/V 和 PCRn 来估计 C0。
本文介绍的方程可以简单、准确地估计每周一次 HD 方案患者的 PCRn。绘制出将 C0 与 PCRn 和 Kru/V 相关联的诺模图可以进一步提高每周一次 HD 方案的安全性。通过多元回归分析建立了以下方程[公式：见文本]，其中 PCRn 是标准化蛋白分解率（PCRn），C0 是透析前血尿素氮浓度（BUN），eKt/V 是平衡的 Kt/V，Kru 是残余肾尿素清除率，V 是透析后尿素分布容积。可以绘制出将透析前 BUN 与 PCRn 和 Kru/V 相关联的诺模图：它不仅可以根据 Kru/V 和透析前 BUN 来估计 PCRn，还可以根据 Kru/V 和 PCRn 来估计透析前 BUN。
