脳死切迫状態の脳波・誘発電位による機能的診断―経頭蓋超音波ドプラ法による血流停止所見との関連から

Electrophysiological evaluatlon of brain function in impending brain death; Temporal correlation with intracranial circulatory arrest.

I．はじめに

　脳死の病態生理において，脳波や誘発電位などの電気生理学的な機能消失と脳循環停止は，その客観的な意義だけでなく，脳機能の不可逆性の判定上も重視されている^49）。この目的に，種々の電気生理学的検査や脳循環測定法が応用されてきたが^49），それぞれ別個に評価され，各検査間の相関関係が必ずしも明確でなく，どの時点でどの検査法を選択すれば，より確実に判定できるのか明らかではない。そこでわれわれは，重症脳障害を伴う切迫脳死患者に対し，主に大脳機能を評価する目的に脳波のcompressed spectral array（CSA）と体性感覚誘発電位（SEP）を，脳幹機能の評価に聴覚脳幹誘発電位（BAEP）とSEPを，脳循環の評価に経頭蓋超音波ドプラ法（TCD）による連続的・多元的な神経モニタリングシステムを導入し，頭蓋内血流停止と大脳・脳幹機能消失との時間的な関連を，その原因となった病態を考慮し検討してきた^35,36）。今回これらの結果を，より詳細に解析し総括するとともに，脳の神経細胞の機能消失と脳死との関連についての考察を行なった。

The aim of this study was to clarify the diagnostic ambiguity caused by discrepancies between electrohysiological loss of neuronal function in the cerebrum and brainstem and intracranial circulatory arrest in impending brain death. One hundred of 203 consecutive patients with severe brain damage were evaluated with a continuous, multimodal neuromonitoring system. The system included somatosensory evoked potentials (SEP) and compressed spectral array (CSA) for the assessment of cerebral cortical function, brainstem auditory evoked potentials (BAEP) and SEP for the evaluation of brainstem neuronal function, and transcranial Doppler sonography (TCD) for the measurement of supratentorial circulation in the middle cerebral artery. Each neuromonitoring modality was conducted serially and assessed every 10-30 minutes. The causes of brain damage were cerebrovascular accident in 52 cases, head injury in 39, brain anoxia in 7, and meningitis in 2. Mean age of the patients was 49 (range, 1-84). Based on CT findings, the cases were classified as supratentorial mass lesions (59 cases), diffuse (32 cases) or infratentorial (9 cases) lesions. Twenty patients who received barbiturate treatment were analyzed separately, as barbiturates may influence CSA findings.