Depner T A, Daugirdas J T
Department of Medicine, University of California at Davis, Sacramento 95817, USA.
J Am Soc Nephrol. 1996 May;7(5):780-5. doi: 10.1681/ASN.V75780.
The normalized protein catabolic rate (PCRn) can be calculated from predialysis and postdialysis BUN measurements in patients receiving intermittent dialysis. This measure of net protein catabolism, adjusted for body size, is a useful clinical measure of nutrition that correlates with patient outcome and, in patients who are in nitrogen balance, is a reasonable estimate of dietary protein intake. Whereas simplified formulae that estimate the per-treatment dose of hemodialysis, expressed as Kt/Vurea (Kt/V), are in common use, simplified methods for determining PCRn have only recently appeared. In the study presented here, equations were derived for calculating PCRn from the predialysis BUN and Kt/V. The equations were of the general form: PCRn = C0/(a + bKt/V + c/(Kt/NLL)) + 0.168, where Co is the predialysis BUN in mg/dL. Three sets of coefficients were developed for patients dialyzed thrice weekly: one for patients dialyzed after the long interval at the beginning of the week, one for patients dialyzed at midweek, and the third for patients dialyzed at the end of the week. Two similar sets of coefficients were developed for patients dialyzed twice weekly. For patients with remaining function in the native kidney remnant, equations were developed and refined for upgrading PCRn by adjusting C0 upward. The equations were validated by comparing the calculated PCRn with PCRn determined by a formal iterative model of urea kinetics in a series of 119 dialyses in 51 patients dialyzed thrice weekly (r = 0.9952; mean absolute error, 1.97 +/- 1.39%) and in a series of 71 dialyses in 25 patients dialyzed twice weekly (r = 0.9956; mean absolute error, 2.17 +/- 1.56%). These simple yet accurate equations should be useful in epidemiologic studies or in clinical laboratories where limited data are available for each patient or when iterative computer techniques cannot be applied.
接受间歇性透析的患者，其标准化蛋白质分解代谢率（PCRn）可根据透析前和透析后的尿素氮（BUN）测量值计算得出。这种经体重校正的净蛋白质分解代谢指标，是一种有用的临床营养指标，与患者预后相关，对于处于氮平衡的患者，它还是膳食蛋白质摄入量的合理估计值。虽然估算每次血液透析治疗剂量的简化公式，即Kt/Vurea（Kt/V）已被广泛应用，但用于确定PCRn的简化方法直到最近才出现。在本文介绍的研究中，推导出了根据透析前BUN和Kt/V计算PCRn的公式。这些公式的一般形式为：PCRn = C0/(a + bKt/V + c/(Kt/NLL)) + 0.168，其中C0是透析前的BUN，单位为mg/dL。为每周透析三次的患者制定了三组系数：一组用于每周开始时经过较长间隔时间后透析的患者，一组用于周中透析的患者，第三组用于周末透析的患者。为每周透析两次的患者制定了两组类似的系数。对于仍保留部分肾功能的患者，通过向上调整C0来推导并完善了用于提高PCRn的公式。通过将计算得出的PCRn与通过尿素动力学的正式迭代模型确定的PCRn进行比较，对这些公式进行了验证。在51例每周透析三次的患者的119次透析中（r = 0.9952；平均绝对误差为1.97±1.39%），以及在25例每周透析两次的患者的71次透析中（r = 0.9956；平均绝对误差为2.17±1.56%）进行了验证。这些简单而准确的公式在流行病学研究或临床实验室中应该很有用，因为在这些情况下，每个患者可获得的数据有限，或者无法应用迭代计算机技术。
