Nguyen Minhtri K, Kurtz Ira
Division of Nephrology, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Room 7-155 Factor Building, Los Angeles, CA 90095-1689, USA.
Clin Exp Nephrol. 2006 Mar;10(1):19-24. doi: 10.1007/s10157-005-0395-2.
The total exchangeable sodium (Na(e)), total exchangeable potassium (K(e)), and total body water (TBW) are the major determinants of the plasma water sodium concentration (Na(+)). The relationship between Na(+) and Na(e), K(e), and TBW was empirically determined by Edelman et al., where: Na(+) = 1.11(Na(e) + K(e))/TBW - 25.6 (Eq. 1). According to Eq. 1, changes in the mass balance of Na(+), K(+), and H(2)O will therefore result in changes in the Na(+). Historically, in evaluating the pathogenesis of the dysnatremias, free water clearance (FWC) and electrolyte-free water clearance (EFWC) have been used to evaluate the pathophysiology of the dysnatremias. However, such analyses are only valid when there is no concomitant input and non-renal output of Na(+), K(+), and H(2)O. Since the classic FWC and EFWC formulas fail to account for the input and non-renal output of Na(+), K(+), and H(2)O, these formulas cannot be used to evaluate the pathogenesis of the dysnatremias or to predict the directional change in the Na(+). In this article, we have addressed this limitation by deriving a new formula, termed whole-body electrolyte-free water clearance (WB-EFWC), which calculates whole-body electrolyte-free water clearance for a given mass balance of Na(+), K(+), and H(2)O, rather than simply the urinary component (FWC, EFWC formulas). Unlike previous formulas, which consider only the renal component of electrolyte-free water clearance, WB-EFWC accounts for all sources of input and output of Na(+), K(+), and H(2)O, and will therefore be helpful in conceptually understanding the basis for changes in the Na(+) in patients with the dysnatremias.
可交换钠总量（Na(e)）、可交换钾总量（K(e)）和总体水（TBW）是血浆水钠浓度（Na⁺）的主要决定因素。Edelman等人通过经验确定了Na⁺与Na(e)、K(e)和TBW之间的关系，即：Na⁺=1.11(Na(e)+K(e))/TBW - 25.6（公式1）。根据公式1，因此，Na⁺、K⁺和H₂O质量平衡的变化将导致Na⁺的变化。从历史上看，在评估钠代谢紊乱的发病机制时，自由水清除率（FWC）和无电解质水清除率（EFWC）已被用于评估钠代谢紊乱的病理生理学。然而，只有在没有Na⁺、K⁺和H₂O的伴随输入和非肾性输出时，此类分析才有效。由于经典的FWC和EFWC公式没有考虑Na⁺、K⁺和H₂O的输入和非肾性输出，这些公式不能用于评估钠代谢紊乱的发病机制或预测Na⁺的方向变化。在本文中，我们通过推导一个新公式，即全身无电解质水清除率（WB-EFWC），解决了这一局限性，该公式计算给定Na⁺、K⁺和H₂O质量平衡下的全身无电解质水清除率，而不是简单地计算尿液成分（FWC、EFWC公式）。与之前仅考虑无电解质水清除率的肾脏成分的公式不同，WB-EFWC考虑了Na⁺、K⁺和H₂O的所有输入和输出来源，因此将有助于从概念上理解钠代谢紊乱患者Na⁺变化的基础。
