Hemodynamic and Metabolic Studies in “Coma Dépassé”. A Search for a Biological Test of Death of the Brain
In a previous study  of comatose patients we noted a striking difference with respect to cerebral hemodynamic and metabolic parameters between apoplectic patients in deep coma and patients in coma dépassé. Table 1 summarizes the results obtained in apoplectic patients in coma, classified according to the level of clinical severity: In the most grave cases (level C4 in our classification), where all reactions to pain as well as corneal reflexes had disappeared, it was found that cerebral metabolism was relatively unaltered. Cerebral blood flow (measured by the 85Krypton inhalation modification of Kety’s method) was lowered by about 50% (in average 26 ml/100 g/min as compared to 46 in normal subjects); cerebral oxygen consumption was proportionally decreased (1.96 ml/100 g/min as compared to 3.34). Cerebral arteriovenous difference of oxygen remained at values close to the normal (5.88 vol. %). Furthermore, in the most serious coma cases a moderate decrease of the arteriovenous glucose difference (−32%) and an increase in cerebral arteriovenous lactic acid difference was noted.
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