全脳虚血による局所脳血流量の変動

CHANGES OF REGIONAL CEREBRAL BLOOD FLOW AFTER TOTAL CEREBRAL ISCHEMIA

I．はじめに

　心肺蘇生後の中枢神経系病変，すなわち全脳血流停止そして脳血流再開後の病態は，脳循環・脳血流の変動により大きく左右される。一般に5分間以上の全脳虚血を持続すると，脳血流を再開しても，脳微小循環障害が発生し，それにともなう脳組織灌流不全が中枢神経機能障害に大きく関与している^1〜6）といわれている。

　しかし，これら脳循環障害の病態は，全脳血流のレベルで，あるいは形態学的に検索されたものが多く，脳の局所領域における血流量変化など脳各部における生理学的変動は十分に検討されているとはいえない。そこで，雑種成犬を用い，8〜10分間の全脳虚血（常温下）を作成し^7〜9），全脳虚血後における局所脳血流量（以下rCBF）の変動を検討した。本論文ではrCBFの変化を中心に全脳血後の中枢神経系病変について若干の知見を得たので報告する。

In normothermic 53 mongrel dogs complete cere-bral circulatory arrest for 8 to 10 min was produced with Aortic occlusion balloon catheter and followed by blood recirculation of the brain for 2 hrs. Local cerebral blood flow in 11 different regions were measured before and after ischemia using radioac-tive labelled microspheres (15±3μm).

Before ischemia, regional blood flow rates within the brain varied between 26.1±5.8 and 61.3±7.9ml/100g/min (means±SD). Reactive hyperemia was present in the brain 8 to 15min after the beginning of the recirculation. Local cerebral blood flow rates increased two to ten times above the control flow, more increased in brain stem, cere-bellum, thalamus and basal ganglia. Regional cerebral blood flow returned to or slightly below normal 30min after ischemia, and subsequentlydecreased 60 to 120 min after ischemia. At 120 min after ischemia local cerebral blood flow rates decreased 40 to 60% of the control flow in cerebral cortices and basal ganglia, 70 to 90% of control flow in subcortical white matter and brain stem.

With these result: 1) There is considerable re-distribution and inhomogeneity of flow rates within the brain after total cerebral ischemia for 8 to 10 min. 2) It is indicated that low flow races of the brain 60 to 120 min after ischemia can not maintain the nutritive blood flow in some cerebral regions, especially in cerebral cortices and basal ganglia. Farther more it may be resulted in secondary brain tissue damage. 3) It is suggested that post-ischemic recirculation may be a factor in the genesis of "selective vulnerability."4) The inhomogeneity of regional cerebral blood flow rates can be associ-ated with the animal species of the dog.