局所脳虚血後の頭蓋内圧亢進に伴う硬膜外圧脈圧変化

CHANGES IN EPIDURAL PULSE PRESSURE IN BRAIN EDEMA FOLLOWING EXPERIMENTAL FOCAL ISCHEMIA

　〈目的〉頭蓋内構成要素のうち脳組織水分含量（脳実質）の増加が頭蓋内圧（ICP）の脈圧（pulse pressure：PP）に及ぼす影響について明らかにするために実験を行った。〈方法〉犬を用いて経眼窩的に一側前大脳動脈A1部とその穿通枝，同側内頸動脈および中大脳動脈M1部を2時間閉塞後6時間再灌流してICPとPPを記録し，同一ICPにおいて大槽内生食注入群のPPと比較した。虚血巣はEvans blue, TTCまたは組織学的に同定し，脳水分含量は湿乾重量法で測定した。〈結果〉梗塞巣の広がりは個体差が大きかったが，尾状核には全例に虚血性変化を認めた。脳水分含量は虚血側で増加した。脳浮腫群では血流再開後，ICPの上昇とともにPPも増大したが，PPは同一ICPでも対象群に比べ有意に小さかった。ICPとPPの回帰直線の傾きは脳浮腫群0.061±0.030（mean±SD），対象群0.107±0.015で脳浮腫群の方が有意に小さかった（P＜0.01）。〈結論〉脳浮腫によるICP充進では，大槽内生食注入によるICP充進に比べてPPが小さかった。このことはPPが頭蓋内構成要素の差（今回の実験では脳組織内水分含量の増加と髄液腔水分含量の増加による差）によって影響を受ける可能性があることを示した。

It is well known that epidural pulse pressure (PP) increases with rising intracranial pressure (ICP). However, PP at the same ICP is not al-ways identical in various intracranial pathologies. Many authors have investigated PP at increased states of ICP, but few studies related to brain ede-ma have been done. This study was carried out in order to clarify the changes of PP in brain edema following focal ischemia. ICP and PP were mea-sured in two groups of anesthetized dogs ; 1) in-creased volume of CSF by cisternal saline injection (control, n=5), 2) brain edema caused by focal is-chemia (edema, n=11). Ischemia was induced by electro-coagulation of the right anterior cerebral artery and by clipping the right middle cerebral artery and right internal carotid artery transorbi-taly. The brain was recirculated for 6 hours after 2 hours of ischemia. The ischemic areas were id-entified by Evans blue, triphenyl tetrazolium chlo-ride (TTC) or histological examination. Water content of the brain was measured by the wet-dry weight method.

The canine focal ischemic model showed consi-stent ischemic damage in the caudate nucleus and produced brain edema successfully. PP increased linearly with rising ICP to 35 mmHg, and PP in the edema group was significantly smaller than that in the control group at the same ICP value. The slopes of the regression equation of ICP and PP were significantly different between the edema and control group (edema : 0.061 ± 0.030, control : 0.107±0.015, mean±SD, p＜ 0.01).

These results suggest that PP is easily affected by ischemic brain edema. Brain edema means in-crease of water content of brain tissue which is one of intracranial components. I would like to con-clude that PP is affected even at the same ICP value when intracranial components have altered.