Fencl V, Jabor A, Kazda A, Figge J
Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115-6110, USA.
Am J Respir Crit Care Med. 2000 Dec;162(6):2246-51. doi: 10.1164/ajrccm.162.6.9904099.
We compare two commonly used diagnostic approaches, one relying on plasma bicarbonate concentration and "anion gap," the other on "base excess," with a third method based on physicochemical principles, for their value in detecting complex metabolic acid-base disturbances. We analyzed arterial blood samples from 152 patients and nine normal subjects for pH, PCO(2), and concentrations of plasma electrolytes and proteins. Ninety-six percent of the patients had serum albumin concentration < or = 3 SD below the mean of the control subjects. In about one-sixth of the patients, base excess and plasma bicarbonate were normal. In a great majority of these apparently normal samples, the third method detected simultaneous presence of acidifying and alkalinizing disturbances, many of them grave. The almost ubiquitous hypoalbuminemia confounded the interpretation of acid-base data when the customary approaches were applied. Base excess missed serious acid-base abnormalities in about one-sixth of the patients; this method fails when the plasma concentrations of the nonbicarbonate buffers (mainly albumin) are abnormal. Anion gap detected a hidden "gap acidosis" in only 31% of those samples with normal plasma bicarbonate in which such acidosis was diagnosed by the third method; when adjusted for hypoalbuminemia, it reliably detected the hidden abnormal anions. The proposed third method identifies and quantifies individual components of complex acid-base abnormalities and provides insights in their pathogenesis.
我们比较了两种常用的诊断方法，一种基于血浆碳酸氢盐浓度和“阴离子间隙”，另一种基于“碱剩余”，并将它们与基于物理化学原理的第三种方法相比较，以评估其在检测复杂代谢性酸碱紊乱方面的价值。我们分析了152例患者和9名正常受试者的动脉血样本，检测其pH值、二氧化碳分压（PCO₂）以及血浆电解质和蛋白质浓度。96%的患者血清白蛋白浓度比对照组均值低3个标准差或更低。约六分之一的患者碱剩余和血浆碳酸氢盐正常。在这些看似正常的样本中，绝大多数通过第三种方法检测到同时存在酸化和碱化紊乱，其中许多情况严重。当应用常规方法时，几乎普遍存在的低白蛋白血症混淆了酸碱数据的解读。碱剩余在约六分之一的患者中漏诊了严重的酸碱异常；当非碳酸氢盐缓冲液（主要是白蛋白）的血浆浓度异常时，该方法失效。阴离子间隙仅在第三种方法诊断为存在酸中毒且血浆碳酸氢盐正常的样本中，检测出了31%的隐匿性“间隙性酸中毒”；校正低白蛋白血症后，它能可靠地检测出隐匿的异常阴离子。所提出的第三种方法能够识别和量化复杂酸碱异常的各个组成部分，并为其发病机制提供见解。
