Medical and Research Services, Veterans Administration Greater Los Angeles Healthcare System, University of California at Los Angeles Membrane Biology Laboratory.
Division of Nephrology, Veterans Administration Greater Los Angeles Healthcare System and David Geffen School of Medicine, Los Angeles, California.
Clin J Am Soc Nephrol. 2018 Feb 7;13(2):343-347. doi: 10.2215/CJN.11941017. Epub 2018 Jan 16.
A reliable determination of blood pH, PCO, and [HCO] is necessary for assessing the acid-base status of a patient. However, most acid-base disorders are first recognized through abnormalities in serum total CO concentration ([TCO]) in venous blood, a surrogate for [HCO]. In screening patients on the basis of serum [TCO], we have been concerned about the wide limits of normal for serum [TCO], 10-13 mEq/L, reported by many clinical laboratories. Indeed, we have encountered patients with serum [TCO] values within the lower or upper end of the normal range of the reporting laboratory, who subsequently were shown to have a cardinal acid-base disorder.Here, we present a patient who had a serum [TCO] within the lower end of the normal range of the clinical laboratory, which resulted in delayed diagnosis of a clinically important "hidden" acid-base disorder. To better define the appropriate limits of normal for serum [TCO], we derived the expected normal range in peripheral venous blood in adults at sea level from carefully conducted acid-base studies. We then compared this range, 23 to 30 mEq/L, to that reported by 64 clinical laboratories, 2 large commercial clinical laboratories, and the major textbook of clinical chemistry. For the most part, the range in the laboratories we queried was substantially different than that we derived and that published in the textbook, with some laboratories reporting values as low as 18-20 mEq/L and as high as 33-35 mEq/L. We conclude that the limits of values of serum [TCO] reported by clinical laboratories are very often inordinately wide and not consistent with the range of normal expected in healthy individuals at sea level. We suggest that the limits of normal of serum [TCO] at sea level be tightened to 23-30 mEq/L. Such correction will ensure recognition of the majority of "hidden" acid-base disorders.
准确测定血液 pH 值、PCO2 和 [HCO3-] 对于评估患者的酸碱状态是必要的。然而，大多数酸碱紊乱首先是通过静脉血血清总 CO 浓度 ([TCO]) 的异常来识别的，[TCO] 是 [HCO3-] 的替代物。在基于血清 [TCO] 对患者进行筛查时，我们一直关注许多临床实验室报告的血清 [TCO] 正常范围很宽，为 10-13 mEq/L。事实上，我们遇到过血清 [TCO] 值在报告实验室正常范围下限或上限内的患者，随后发现他们患有主要的酸碱紊乱。在这里，我们介绍了一位患者的血清 [TCO] 值处于临床实验室正常范围的下限，这导致了对一种临床上重要的“隐匿性”酸碱紊乱的诊断延迟。为了更好地确定血清 [TCO] 的适当正常范围，我们从精心进行的酸碱研究中得出了海平面成年人外周静脉血的预期正常范围。然后，我们将这个范围（23-30 mEq/L）与 64 个临床实验室、2 个大型商业临床实验室和临床化学主要教科书报告的范围进行了比较。在大多数情况下，我们询问的实验室范围与我们推导的范围和教科书上公布的范围有很大的不同，一些实验室报告的范围低至 18-20 mEq/L，高至 33-35 mEq/L。我们得出结论，临床实验室报告的血清 [TCO] 值范围非常广泛，且往往与海平面健康个体的正常范围不一致。我们建议将海平面血清 [TCO] 的正常范围下限收紧至 23-30 mEq/L。这种校正将确保识别出大多数“隐匿性”酸碱紊乱。
