代谢性酸中毒犬脑脊液［HCO－_3］与Pco_2的关系

Relationship between cerebrospinal fluid HCO - 3 concentration and cerebrospinal fluid P CO 2 in acute metabolic acidosis in dog

作者旨在探讨代谢性酸中毒时脑脊液（ＣＳＦ）［ＨＣＯ－３］与ＰＣＯ２的相互关系。两组代谢性酸中毒模型均由静脉内输入０．２ｍｏｌ／ＬＨＣＩ产生，［ＨＣＯ－３］ａ１ｈ内下降到（１２２）ｍｍｏｌ／Ｌ。实验６ｈ时ＣＳＦ［ＨＣＯ－３］：１组（正常碳酸血性代酸）下降了１．６ｍｍｏｌ／Ｌ；组（低碳酸血性代酸）下降了７．０ｍｍｏｌ／Ｌ．ＣＳＦ［ＨＣＯ－３］与ＣＳＦＰｃｏ２，显著正相关（ｒ＝０．８３４，Ｐ＜０．０ｌ）．结果说明代谢性酸中毒时ＣＳＦ［ＨＣＯ－３］并不受［ＨＣＯ－３］ａ的明显影响，主要取决于ＣＳＦＰｃｏ２的变化，其调节机制与脉络丛上皮细胞内ＣＯ２的水化作用和ＣＡ活性有关。

The present experiment was designed to study the relationship between cerebrospinal fluid (CSF) HCO - 3 concentration and CSF P CO 2 in acute metabolic acidosis. The acid base variables of both arterial blood and CSF in two groups of dogs were determined. (1) Five dogs were kept isocapnic while metabolic acidosis was induced. The cisternal CSF HCO - 3 registered only a 1.6 mmol/L drop six hours later and was not significantly different from control. (2) In five dogs metabolic acidosis was induced while the dogs were mechanically hyperventilated. CSF HCO - 3 dropped by 7 mmol/L six hours later. Remarkably different from control, CSF HCO - 3 showed a significant positive correlation with CSF P CO 2 ( r =0.834, P <0.01). These results suggest that CSF HCO - 3 is dependent upon P CO 2 but not evidently upon [HCO - 3]a. The formation of HCO - 3 in CSF is closely related to P CO 2 and the activity of carbonic anhydrase.