Moviat Miriam, Terpstra Anniek M, Ruitenbeek Wim, Kluijtmans Leo A J, Pickkers Peter, van der Hoeven Johannes G
Department of Intensive Care Medicine, Radboud University Nijmegen Medical Centre, The Netherlands.
Crit Care Med. 2008 Mar;36(3):752-8. doi: 10.1097/CCM.0B013E31816443CB.
The physicochemical approach, described by Stewart to investigate the acid-base balance, includes the strong ion gap (SIG), a quantitative measure of "unmeasured" anions, which strongly correlates to the corrected anion gap. The chemical nature of these anions is for the most part unknown. We hypothesized that amino acids, uric acid, and organic acids could contribute to the SIG.
Prospective observational study.
Intensive care department of an academic hospital.
Consecutive intensive care unit patients (n = 31) with metabolic acidosis, defined as a pH of < 7.35 and a base excess of < or = -5 mmol/L.
A single arterial blood sample was collected.
The SIG was calculated and two groups were compared: patients with SIG of < or = 2 mEq/L and patients with SIG of > or = 5 mEq/L. "Unmeasured" anions were examined by ion-exchange column chromatography, reverse-phase high-performance liquid chromatography, and gas chromatography/mass spectrometry measuring amino acids, uric acid, and organic acids, respectively.
Comparison of patient characteristics of both SIG groups showed that age, sex, Acute Physiology and Chronic Health Evaluation II, pH, base excess, and lactate were not significantly different. Renal insufficiency and sepsis were more prevalent in the SIG > or = 5 mEq/L group (n = 12; median SIG, 8.3 mEq/L), associated with higher mortality. Concentrations of the anionic compounds aspartic acid, uric acid, succinic acid, pyroglutamic acid, p-hydroxyphenyllactic acid, and the semiquantified organic acid homovanillic acid were all statistically significantly elevated in the SIG > or = 5 mEq/L group compared with the SIG < or = 2 mEq/L group (n = 8; median SIG, 0.6 mEq/L). Overall, the averaged difference between both SIG groups in total anionic amino acids, uric acid, and organic acids concentrations contributed to the SIG for, respectively, 0.07% (5 microEq/L, p = not significant), 2.2% (169 microEq/L, p = .021), and 5.6% (430 microEq/L, p = .025).
Amino acids, uric acid, and organic acids together accounted for only 7.9% of the SIG in intensive care unit patients with metabolic acidosis.
斯图尔特描述的用于研究酸碱平衡的物理化学方法包括强离子间隙（SIG），这是一种对“未测定”阴离子的定量测量方法，它与校正阴离子间隙密切相关。这些阴离子的化学性质大多未知。我们假设氨基酸、尿酸和有机酸可能对SIG有贡献。
前瞻性观察性研究。
一家学术医院的重症监护病房。
连续入住重症监护病房的患者（n = 31），代谢性酸中毒定义为pH值<7.35且碱剩余<或=-5 mmol/L。
采集一份动脉血样本。
计算SIG并比较两组：SIG≤2 mEq/L的患者和SIG≥5 mEq/L的患者。分别通过离子交换柱色谱法、反相高效液相色谱法和气相色谱/质谱法检测“未测定”阴离子，以测量氨基酸、尿酸和有机酸。
两组SIG患者的特征比较显示，年龄、性别、急性生理与慢性健康状况评分II、pH值、碱剩余和乳酸水平无显著差异。肾功能不全和脓毒症在SIG≥5 mEq/L组（n = 12；SIG中位数为8.3 mEq/L）中更为常见，且死亡率更高。与SIG≤2 mEq/L组（n = 8；SIG中位数为0.6 mEq/L）相比，SIG≥5 mEq/L组中阴离子化合物天冬氨酸、尿酸、琥珀酸、焦谷氨酸、对羟基苯乳酸和半定量有机酸高香草酸的浓度均有统计学显著升高。总体而言，两组SIG患者在总阴离子氨基酸、尿酸和有机酸浓度上的平均差异对SIG的贡献分别为0.07%（5微当量/升），p = 无显著差异）、2.2%（169微当量/升，p = 0.021）和5.6%（430微当量/升，p = 0.025）。
在患有代谢性酸中毒的重症监护病房患者中，氨基酸、尿酸和有机酸共同仅占SIG的7.9%。
