脳死に関する脳の組織計量的研究  [in Japanese] Autolysis of Cerebral Tissue Assessed as Possible Indicator of Brain Death  [in Japanese]

脳死7例・対照7例の大脳・脳幹・小脳の各HE標本について,神経細胞の変性や赤血球の崩壊などの死後変化所見を(1)〜(6)の指数で現わし,A時間(心停止〜解剖)とB時間(脳死判定〜解剖)との相関性を検討した。なお,(1)は神経細胞の変性,(2)は赤血球の崩壊,(3)は血管内皮細胞の剥離,(4)は細菌増殖の程度をそれぞれ示す指数で,(5)指数は,脳の死後変化を単一の数値で現わすための試みで算出された(1)〜(4)指数の合計値である。対照例(A時間:6時間〜7日)では各指数とA時間との相関は高く,いずれの指数も脳における死後変化を示す指標としては有効(特に(5)指数)と思われた。一方,脳死例(A時間:5〜24時間,B時間:15時間〜4日)では各指数はA時間よりもB時間との相関が高く,特に小脳における(5)指数とB時間との間には高い相関が認められた。したがって,小脳の(5)指数を参考にすれば,脳死判定時期の推測が可能と思考される。また,小脳における顆粒層崩壊((6)指数)も脳死状態を示唆する所見であって,同様に脳死判定時期の推測に有効と思われた。

The determination of brain death, presupposing absoluteness of all the criteria, behooves the analysis of tissue to be as precise as possible. To assure definitive histological analysis of cerebral tissue in patients pronounced brain dead, we devised a critical method of scoring the tissue and tested the reliability of the technique in 14 autopsies. A numerical stage of (1) to (6) was assigned to the tissue according to postmortem changes disclosed by hematoxylin-eosin stain. Then the tissue at each stage was assessed by further histological analysis and evaluated with a fine-tuned index. In nerve cells (the stage (1)), erythrocytes (the stage (2)), and endothelia (the stage (3)), the extent of each autolysis was designated by a score of 0 to 300. In bacterial colonies (the stage (4)), the extent of putrefaction was designated by a score of 0 to 100. The stage (5) denoted the sum of the indices for the tissue represented in stages (1) to (4). Then the stage (5) histological index was designated by a score of 0 to 1000. And the stage (6) referred to autolysis in the granular layer of cerebellum. Particulary to elucidate the possible relationship between the indices of postmortem autolysis and the interval from cardiac arrest to autopsy (interval A) or the period from initial judgement of brain death to autopsy (interval B), analysis was made on tissue taken from the various parts of the brain in autopsies ranging from 5 hours to 7 days postmortem. In the present cadavers, the cause of death in 7 cases associated with brain death was intracranial injury or secondary drowning, and in 7 cases not associated with brain death (control group) the cause of death was acute myocardial infarction, idiopathic cardiomyopathy, asphyxia, drowning, or shock due to anesthesia. The results of the present study were as follows: (1) In the controls a significant correlation was consistently found between interval A (6 h to 7 d) and the stage (5) histological indices for tissue from all the cerebral sites studied, i. e. the longer the lapse of time after cardiac arrest the higher the index. The correlation coefficients, all statistically significant (p<0.001), were as follows: endbrain 0.987, midbrain 0.987, pons 0.985, medulla oblongata 0.980, and cerebellum 0.984. (2) In the cadavers associated with brain death, although no relationship was indicated between most of the histological indices and interval A (5-24 h), a close correlation was seen between several indices and interval B (15 h to 4 d), particularly in the stage (5) values as illustrated by the correlation coefficients for the following parts of the brain : endbrain 0.769, pons 0.926, medulla oblongata 0.772, and cerebellum 0.935. With the sole exception of that of midbrain tissue (0.653), the correlation coefficients were statistically significant (p<0.01). Essentially, the higher indices corresponded to the longer lapse of time after initial judgement of brain death, with negligible regard for the period following cardiac arrest. These results suggest that, in cases not associated with brain death, stage (5) histological indices in the present study may reliably indicate the time of cardiac arrest, whereas in brain death the stage (5) histological indices may be employed as a reliable determinant of the time of brain death. As a further marker of brain death, the stage (6) histological indices showed that postmortem autolysis in the granular layer of cerebellum varies with the passing of time.