Kessler E, Ritchey N P, Castro F, Caccamo L P, Carter K J, Erickson B A
Department of Internal Medicine, St. Elizabeth Medical Health Center, Youngstown State University, Youngstown, Ohio, USA.
Am J Nephrol. 1998;18(6):471-7. doi: 10.1159/000013390.
Based mainly on the simplicity of its calculation, the urea reduction ratio (URR) has been suggested as an alternative to urea kinetic modeling (Kt/V) as a measure of hemodialysis adequacy. However, recent studies have raised questions concerning the accuracy of URR, particularly in the presence of residual kidney function (KrU). This study was initiated to evaluate the relationship between URR and Kt/V under a variety of dialysis conditions. Equations based on the variable-volume, single-pool model described by Gotch were used to construct a model incorporating the variables used in the estimation of URR and Kt/V. The model's prediction of URR correlated closely with measured URR in 30 patients (r = 0.9987, p < 0.000001). This analytic approach showed that changes in each of several dialysis parameters caused divergence in the values of URR and Kt/V. The model showed that URR could be less than 0.65, while total Kt/V was greater than 1.2, whether or not KrU was present. In fact, when KrU was greater than 1. 0, URR could be less than 0.65, while Kt/V might be 2.0 or higher. On the other hand, the model showed instances where URR could be greater than 0.65, when Kt/V was less than 1.2. This occurred only when KrU was less than 1.0. To determine the prevalence of these anomalies in clinical practice, 767 kinetic modeling determinations were evaluated in 207 patients. One of the above discrepancies was observed at least once in 30.9% of the patients, representing 12.1% of all determinations. In addition, it was found that omitting KrU from the calculation of Kt/V generally leads to a Kt/V <1.2. This, when associated with a URR <0.65, could erroneously imply inadequate dialysis. The patient data are consistent with the view that URR and Kt/V are the net result of several variables that may act together or even in opposing directions. Based on this mathematical model and the observed clinical data, the use of URR alone to assess dialysis adequacy, or neglecting the contribution of KrU to Kt/V, may lead to changes in the dialysis prescription that are neither correct nor necessary.
主要基于计算的简便性，尿素清除率（URR）已被提议作为尿素动力学建模（Kt/V）的替代指标，用于衡量血液透析充分性。然而，近期研究对URR的准确性提出了质疑，尤其是在存在残余肾功能（KrU）的情况下。本研究旨在评估在各种透析条件下URR与Kt/V之间的关系。基于Gotch描述的可变容积单池模型的方程，构建了一个包含用于估算URR和Kt/V的变量的模型。该模型对URR的预测与30例患者的实测URR密切相关（r = 0.9987，p < 0.000001）。这种分析方法表明，几个透析参数中的每一个变化都会导致URR和Kt/V值出现差异。该模型显示，无论是否存在KrU，URR可能小于0.65，而总Kt/V大于1.2。实际上，当KrU大于1.0时，URR可能小于0.65，而Kt/V可能为2.0或更高。另一方面，该模型显示，当Kt/V小于1.2时，URR可能大于0.65的情况。这种情况仅在KrU小于1.0时发生。为了确定这些异常情况在临床实践中的发生率，对207例患者的767次动力学建模测定进行了评估。在30.9%的患者中至少观察到上述差异之一，占所有测定的12.1%。此外，发现从Kt/V的计算中忽略KrU通常会导致Kt/V <1.2。当这与URR <0.65相关联时，可能会错误地暗示透析不充分。患者数据与以下观点一致，即URR和Kt/V是几个可能共同作用甚至方向相反的变量的净结果。基于这个数学模型和观察到的临床数据，仅使用URR来评估透析充分性，或忽略KrU对Kt/V的贡献，可能会导致透析处方的改变，既不正确也不必要。
