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Brain and Nerve No to Shinkei Volume 37, Issue 12 （December 1985）

Brain and Nerve 脳と神経 37巻12号（1985年12月発行）

Japanese English

原著

脳循環のautoregulation, CO₂反応性と大脳皮質酸素分圧の関連 AUTOREGULATlON AND CO₂ RESPONSE Of CORTICAL BLOOD FLOW AND THEIR RELATIONSHIP TO CORTICAL OXYGEN TENSION 田口芳雄 ¹ , George M．　Austin ^2,3 Yoshio Taguchi ¹ ¹東京慈恵会医科大学脳神経外科 ²The Stroke Research Foundation at The Institute of Environmental Stress, University of California ³Department of Neurosurgery, University of Southern California ¹Department of Neurosurgery, The Jikei University School of Medicine pp.1163-1171

発行日 1985年12月1日 Published Date 1985/12/1

DOI https://doi.org/10.11477/mf.1406205624

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Abstract 文献概要
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　抄録　脳循環のautoregutation （自動調節能)と脳酸素分圧の関連については明確な説明が得られていない。われわれはNew Zealand white rabbitを用いて大脳皮質血流量（CoBF），および大脳皮質酸素分圧（bPO₂）について，全身血圧の変動に際し，両者を連続的に測定し，自動調節能の作動範囲を求め，その関連を検討した。さらに，両者のCO₂反応性についても検索かた。CoBFについては平均動脈血圧（MABP）80—100 mmHgが自動調節能の作動範囲と考えられ，bPO2については有意に広範囲で一定に保たれた。CO₂反応性はPaCO₂　18.3-63.2mmHgの範囲において，CoBF,bPO₂ともに直線的であり，その際，MABP，PaO₂の値を補正すると，CoBFの変化率は2.09％／mmHg,bPO₂の変化率は1.48％／mmHgであり，両者間に有意の差がみられた。これらの結果は大脳皮質における酸素分圧のより高い恒常性を示唆し，このことは脳の機能とcortical oxidative metabolismを考慮すると，生体にとって極めて有利な機構と考えられる。

Autoregulation and CO₂ response of cortical blood flow and their relationship to cortical oxy-gen tension is not fully known.

We have examined autoregulation and CO₂ re-sponse of local cortical blood flow (CoBF) and cortical oxygen tension (bPO₂), using 41 New Zealand white rabbits. CoBF was measured con-tinuously by using the heated thermocouple tech-nique and bPO₂ was monitored by the polarogra-phic method. Intravenous injection of phenyle-phrine hydrochloride or trimethaphan camsylate was used to test for autoregulation by increasing or decreasing perfusion pressure. The data was analyzed in the range between 50 and 140 mmHg of mean arterial blood pressure (MABP). The range of autoregulation was determined by our own analytical method.

PaCO₂ was manipulated between 18. 3 and 63. 2 mmHg. It was increased by raising the concentra-tion of CO₂ in the inspired gas mixture. Hypoca-pnia was induced by hyperventilation.

The mean values of CoBF and bPO₂ were 36.2 ±5.3 m//100 g/min and 32.9 ± 12.8 mmHg respec-tively at 90 mmHg of MABP during the test for autoregulation. The changes in both CoBF and bPO₂ with changing perfusion pressure were often relatively small at near baseline blood pressure and became more pronounced with large increase or decrease in MABP. On returning from highMABP to baseline blood pressure, a hysteresis effect on CoBF was observed in 20 out of twenty two cases. The autoregulation of CoBF was main-tained in the range between 80 and 100 mmHg of MABP. On the other hand, bPO₂ was maintained constant in the range between 75 and 110 mmHg of MABP. This range was significantly wider than that of CoBF (p <0. 01).

The changes of CoBF and bPO₂ in response to changes of PaCO₂ showed linear fashion. The per-cent change of CoBF was 2.33 %/mmHg, corre-sponding 0.85 ml/100 g/min, and the percent change of bPO₂ was 1.95%/mmElg. There was no significant difference between them. However, when CO₂ response was tested, there were somedegree of changes in MABP and PaO₂, having considerable effect on bPO₂ and CoBF. After be-ing corrected by using our data obtained in the test for autoregulation, the percent change became to be 2.09%/mmHg. This corresponded to 0.76 ml/100 g/min. The percent change of bPO₂ became to be 1.48%/mmHg. And the changing rate of bPO₂ was significantly smaller than that of CoBF (p <0.01).

We conclude that cortical oxygen tension is maintained more constant than cortical blood flow. It seems to be very convenient for cortical oxi-dative metabolism to maintain brain function.