J.Jpn. Surg. Soc.. 57(11): 1829-1852, 1957
EXPERIMENTAL STUDIES ON THE BRAIN CIRCULATION FROM THE VIEWPOINT OF CARDIAC SURGERY
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Surgical Department, Tokyo Womens Medical College (Director; Prof. Shigeru SAKAKIBARA) Shigeo TSUBOI |
The cerebral blood flow and oxygen consumption of brain decreased while the cerebral vascular resistance increased. Although the decreased cardiac output in acuired heart disesses will decrease the cerebral blood flow, it seems that the increase of the cerebral vascular resistance is more important for the decrease of cerebcal blood flow. According to prof. Imai (Pathogical Department, Tokyo Women's Medical College) the adventitia of cerebral arteiosis showed fifiosis in most of the cases with acquired heart diseases. Consequently, the increase in the cerebral vascular resistance seems partly due to the organic changes of the cerebral arteriosis. In these patients with decreased cerebral circulation, the cerebral blood flow increased and the cerebral vascular resistance decreases after surgical treatment. Therefore, this decrease is not necessary caused by the organic changes of the blood vessels alone, but the functional factor must be considered.
II) The influences of surgical operation on the cerebral circulation were studied on dogs with experimentally produced acquired heart diseases. The effect of narcosis, thoracotomy, bleeding and anoxia were studied in these animals and control animalsi with electromagnetic flow meter. The rate of reduction of the cerebral blood flow is larger in these animals compared with in the normal animals. When the increase of cerebral blood flow becomes necessary, it increased sufficiently in normal animal, but it did not increase enough in these animals with heart diseases. During various operations on the acquired heart diseases, cerebral blood flow tended to drops fouther in requirement of the brain.
III) Most cases of acquired heart diseases occurred in adult and show same degree of myocardial damage, so that interruption of circulation under hypothermia seems to be more dangerous in acquired heart diseases than in congenital one. Furthermore the decreased cerebral blood flow and poor adaptation for anoxic condition increase the danger in this condition. In order to avoid the interruption of general ciculation the use of the artificial heart lung machine is the ideal method for the operations under direct vision. But at present it is difficult to circulate the sufficient amount of blood with this machine, because there are several problems to be solved for this procedure. Therefore, it was designed to circulate the minimal necessary volume of blood during operation. The minimal necessary amount of blood was determined by the author with animal experiments .
Brachiocephalic arteries were ligated at the point of branchy from the aorta, left subclavial artery was ligated 3 cm distal from the aorta, left internal carotid artery and left subclavial actery were connected together. Thus, cerebral blood flow was restricted only through this artery. Electromagnetic flowmeter was inserted into this artery and minimal necessary cerebral blood flow was determined by the amount of blood to survive the animal safely for a definite time. According to these experiments the minimal necessary blood volume varied in acaccordance to the time of circulation. The minimal necessary brain circulation blood volume to maintain the animal safely for 30 minites was found to be 14 cc/min/100g barn.
In order to obtain this amount of cerebral bloodflow, 300cc/min. of blood was necessary to be sent into the aorta according to the experiment with about 10 kg dog. If the descending aorta was temporally occluded, 200cc/min. of blood was enough.
The average weight of the brain of the Japanese is 1300 gr. and weight of brain of 10 kg. dog is 70 gr. and weight of brain of 10 kg. dog is 70 gr. If the minimal necessary volume studied with dogs is taken to be 14cc/min. the minimal necessary cerebral blood flow for the humans would be 182cc/min. and it would be necessary to send 1174.2cc/min. of blood into artery to reach this volume of cerebral circulation. If an interruption of the aorta is made simultaneously, 364cc/min. would be sufficient.
These results of experimental studies were applied clinically and the data obtained in clinical cases suggested that the result of the author's experimental work was applicable to patient.
(author's abstract)
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