Paulson W D
Department of Medicine, Louisiana State University Medical Center, Shreveport 71130, USA.
J Am Soc Nephrol. 1996 Feb;7(2):357-63. doi: 10.1681/ASN.V72357.
The serum anion gap is decreased in hyperchloremic (HCl) acidosis and increased in diuretic-induced alkalosis. These anion gap changes have been largely attributed to titration-induced variations in the net negative charge of the serum proteins, which are the predominant non-HCO3 buffers of serum. It has recently been shown, however, that albumin has all of the net protein charge, and titration-induced changes in charge are smaller than have been widely believed. Because the non-HCO3 buffers are also titrated in acute hypocapnia and hypercapnia, these disorders were induced in 16 anesthetized dogs for 10 min in order to assess the effect of acute changes in pH on the anion gap. Although the mean arterial pH varied from 7.04 to 7.65, the calculated mean albumin charge only varied from 6.8 to 9.0 mEq/L. When the anion gap was computed with HCO3 (AGHCO3 = Na + K - Cl - HCO3), the change in AGHCO3 per 0.1 change in pH (delta AGHCO3/ delta pH) was only 0.15 mEq/L per 0.1 pH. When the anion gap was computed with total CO2 content (AGTCO2 = Na + K - Cl - TCO2), delta AGTCO2/delta pH was larger (0.51 mEq/L per 0.1 pH) because of the effect of variable PCO2 levels on TCO2. In a review of 22 previous studies in humans and dogs, similar estimates of delta AG/delta pH were obtained (after adjusting for the lower albumin level in dogs). These results show that simple titration processes that occur within 10 min of a change in pH cause minimal changes in the anion gap. Titration of the known non-HCO3 buffers of serum does not explain the much larger anion gap changes of HCl acidosis and diuretic alkalosis.
血清阴离子间隙在高氯性（HCl）酸中毒时降低，在利尿剂诱发的碱中毒时升高。这些阴离子间隙变化很大程度上归因于血清蛋白净负电荷的滴定诱导变化，血清蛋白是血清中主要的非HCO3缓冲剂。然而，最近的研究表明，白蛋白承担了所有的蛋白质净电荷，且滴定诱导的电荷变化比人们普遍认为的要小。由于非HCO3缓冲剂在急性低碳酸血症和高碳酸血症时也会被滴定，因此在16只麻醉犬身上诱发这两种紊乱状态持续10分钟，以评估pH值急性变化对阴离子间隙的影响。尽管平均动脉pH值在7.04至7.65之间变化，但计算得出的平均白蛋白电荷仅在6.8至9.0 mEq/L之间变化。当用HCO3计算阴离子间隙（AGHCO3 = Na + K - Cl - HCO3）时，pH每变化0.1时AGHCO3的变化（δAGHCO3/δpH）仅为每0.1 pH变化0.15 mEq/L。当用总CO2含量计算阴离子间隙（AGTCO2 = Na + K - Cl - TCO2）时，由于PCO2水平变化对TCO2的影响，δAGTCO2/δpH更大（每0.1 pH变化0.51 mEq/L）。在对之前22项针对人类和犬类的研究进行综述时，得到了类似的δAG/δpH估计值（在对犬类较低的白蛋白水平进行调整后）。这些结果表明，在pH值变化10分钟内发生的简单滴定过程只会导致阴离子间隙的微小变化。血清中已知的非HCO3缓冲剂的滴定并不能解释HCl酸中毒和利尿剂碱中毒时阴离子间隙的大得多的变化。
