[Existence of triphasic flow pattern in regional cerebral blood flow of prolonged unconscious patients (author's...

Anticipating to get some new informations about the cerebral circulations of the comatous patients, two kinds of radioisotopic techniques were combined and applied to twelve unconscious patients of various etiologies. The first step was the conventional gas clearance method using xenon 133 as the indicator. Regional cerebral blood flows were measured at the six areas over each hemisphere. Immediately following this procedure, about 150 muCi of I-131 MAA (I-31 macroaggregated human serum albumin) were injected into internal carotid artery via the same catheter inserted already for the first procedure. Radioactivities of the head and lungs were measured and the relative shunt flow was calculated based on the formula already described elsewhere. Profil scanning of the whole body of the patient was also performed after the intracarotid injection of I-131 MAA. Consciousness states of the ten patients were all severely damaged and causes of the disturbed consciousness were various, including 5 of subdural hematoma, 2 of occlusive cerebrovascular disease, 2 of brain tumor and 1 of ruptured intracranial aneurysm. This investigation revealed the following results; 1) In all patients, regional cerebral blood flows were shown decreased over all areas detected. The regional cerebral blood flows could not be increased by 5% carbon dioxide inhalation, suggesting angioparalysis in these areas. 2) Graphical analysis of the clearance curves revealed triphasic flow pattern in rCBF in four cases. In three cases among the four, the intracarotid injection of I-131 MAA showed the radioisotope labelled particles were captured not only in the brain, but also in the lungs and the relative shunt flow calculated increased up to twice as much as normal controls. It indicates that some of the particles larger than the cerebral capillary size passed through the brain and were captured by the capillary net work of the lungs. From the above described data, it might be concluded that the initial rapid component of triphasic flow pattern in rCBF measurement does not represent the hyperemia of luxury perfusion of metabolic origin, but arteriovenous shunting blood flow, probably, through the precapillary thoroughfare channels which have been anatomically demonstrated by Hasegawa et al.