Incongruence between new ideas and current concepts fuels scientific progress. Within acid-base physiology, an—apparently new—idea of a ‘strong ion difference’ in plasma (SID) was introduced by Stewart some 40 years ago.^1-3 SID is ‘the sum of all strong base cation concentrations minus the sum of all strong acid anion concentrations’,² in clinical practice often ([Na⁺] + [K⁺] − [Cl⁻]) in mmol/l. Subsequently, the concept was extended to renal function, and recently this was the focus of an editorial in the journal,⁴ henceforth the editorial. The arguments in the editorial are difficult to follow mainly because (a) they seem to violate the fundamental principle of electroneutrality, (b) they question the mere existence of transmembrane transport of protons and bicarbonate ions and (c) they include peculiar cause-effect relationships for which there are little documentation in the literature. These issues will be discussed below, and—as this is difficult without reference to their background—the ideas of Stewart will be commented. The discussion includes numerical examples taken from a quantitative overview (Figure 1) of essential cause-and-effect relationships representative of a normal person on a typical (H⁺ generating) Western diet.

新思想与当前概念之间的不一致推动了科学进步。在酸碱生理学中，大约 40 年前，Stewart 引入了一种——显然是新的——血浆中“强离子差异”的想法 (SID)。^1-3 SID 是“所有强碱阳离子浓度的总和减去所有强酸阴离子浓度的总和”，²在临床实践中经常 ([Na ⁺ ] + [K ⁺ ] − [Cl ⁻ ])，单位为 mmol/l . 随后，这个概念被扩展到肾功能，最近这是该杂志社论的焦点，⁴此后的社论。社论中的论点难以理解，主要是因为（a）它们似乎违反了电中性的基本原理，（b）它们质疑质子和碳酸氢根离子跨膜传输的存在和（c）它们包括特殊的因果关系文献中的文献很少。这些问题将在下面讨论，并且——因为如果不参考它们的背景就很难——斯图尔特的想法将被评论。讨论包括从典型（H ⁺生成）西方饮食中代表正常人的基本因果关系的定量概述（图 1）中获取的数值示例。