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Brain and Nerve No to Shinkei Volume 28, Issue 10 （October 1976）

Brain and Nerve 脳と神経 28巻10号（1976年10月発行）

Japanese English

原著

O₂の脳血管収縮作用におけるCO₂の役割 INFLUENCE OF CO₂ ON CEREBRAL VASOCONSTRICTING EFFECT OF O₂ 藤本俊一郎 ¹ , 長尾省吾 ¹ , 久山秀幸 ¹ , 西本健 ¹ , 二宮一彦 ¹ , 秋岡達郎 ¹ , 野坂芳樹 ¹ , 西本詮 ¹ , 萱田静海 ² , 奥村修三 ³ Syunichiro Fujimoto ¹ , Seigo Nagao ¹ , Hideyuki Kuyama ¹ , Ken Nishimoto ¹ , Kazuhiko Ninomiya ¹ , Tatsuro Akioka ¹ , Yoshiki Nosaka ¹ , Akira Nishimoto ¹ , Shizumi Kayata ² , Syuzo Okumura ³ ¹岡山大学脳神経外科 ²香川労災病院 ³国立岡山病院脳神経外科 ¹Department of Neurological Surgery, Okayama University Medical School ²Kagawa Labor Welfare Projects Corporation Hospital ³Department of Neurological Surgery, Okayama National Hospital pp.1141-1147

発行日 1976年10月1日 Published Date 1976/10/1

DOI https://doi.org/10.11477/mf.1406203962

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Abstract 文献概要
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I．はじめに

　重症頭部外傷などの頭蓋内圧亢進時においては脳血流が減少する結果，脳組織CO₂の蓄積，脳組織hypoxiaをきたし，代謝はanaerobic glycolysisに傾くことが報告されている。脳組織中にCO₂と酸性代謝物質の蓄積が相まつて脳組織がacidosisに傾く結果，脳血管緊張が低下し，脳血管拡張，脳血管床増大をきたし，頭蓋内圧はさらに上昇すると考えられている^{6,11,15,24）}。

　近年高濃度酸素吸入（oxygenation at high pressure，　以下OHPと略す）のarterial hyperoxygenationによる脳hypoxiaの改善，脳血管収縮作用に着目して，このような頭蓋内圧亢進時の病態の改善を計ろうとする試みがある^{4,10,20,25）}。

50 mongrel adult dogs were used to study the influence of CO₂ on cerebral vasoconstricting effect of O₂. Oxygenation was performed at 1 ATA O₂ and 2 ATA O₂. Responses of the cerebral vascular bed to oxygenation were assessed by changes of CSF pressure which was measured in the cisterna magna.

In order to study the influence of arterial CO₂ on the cerebral vasoconstricting effect of O₂, PaCO₂ was maintained at 20, 40 and 60mmHg respectively, at which level oxygenations were performed. And changes of CSF pressure during oxygenation were compared with each other.

In another study, prior to oxygenation, acetazo-lamide 50mg/kg was intravenously injected to in-hibit the effect of arterial and brain tissue CO₂ on the cerebrovascular bed, and then the changes of CSF pressure were compared between in acetazo-lamide treated and untreated group.

Results were as follows:

1. The cerebral vasoconstricting effect of O₂ was the greatest at PaCO₂ 40 mmHg (normocapnia), moderate at PaCO₂ 60 mmHg (hypercapnia) and slight in degree at PaCO₂ 20mmHg (hypocapnia).

This study demonstrated that vasoconstricting effect of O₂ in various degrees of intracranial hypertension was maximal in normocapnia but diminished in pathological conditions such as hyper-capnia and paticularly in hypocapnia.

2. CSF pressure was definitely lowered by oxy-genation in the group treated with acetazolamide which inhibits the effect of CO₂ on the cerebral vessels as untreated group.

Concerning the mechanism of action of O₂, this result indicates that O₂ has a vasoconstricting effect by acting directly on the cerebral vascular smooth muscle, independently of arterial and brain tissue CO₂.