J.Jpn. Surg. Soc.. 57(8): 1287-1328, 1956

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STUDIES ON PROLONGATION OF THE DURATION OF CIRCULATORY INTERRUPTION PERIOD. (ESPECIALLY ON THE HEAD COOLING)

Intracardiac surgery under direct vision requires circulatory interruption. Since the interruption can be safely allowed only for an extremely short time, the safe interruption time has to be somehow prolonged sufficiently for the surgical operation. Already in 1950, Bigelow reported that the cardiac occlusion safely prolonged under general hypothermia. We reexamined this method by animal experiments and following th reports by Lewis, Swan, Bailey and others of their clinical adaptation of this methor, we succeeded clinically in open heart surgery under direct vision. In the method known at that time, the cooling was done only for below the neck, the head being left uncooled. In this method it was found by us that temperature of the brain was higher than the rest of the body and oxygen cousumption was relatively less than in the rest of the body. For this reason a long cardiac Occlusion led to death of animal due to brain damages. The safe circulatory interuption time of this method was found to be only fiften to twenty minutes for healthy dogs. A method of cooling the head onlv was then tried and it was found that the temperature and oxygen consumption were lowered remarkably in the brain as compared with the rest of the body. By this method healthy dogs were found to stand the cardiac occlusion for as long as 30 minutes.
Clinical applications of this method have been very successful. Experiments on the effects of the circulatory interuption on the myocardium had indicated that the lower the temperature of the my cardium the longer the possible time of interupt ion. However, too great a lowering of the temperature of the heart was apt to cause ventricular fibrillation. Therefore, various experiments were conducted and it was found that such difficulties would hardlyoccur, should the temperature be lowered slowly. Accordingly, we had used a method whereby the entire body is immersed in ice water and cooled slowly and gradually.
As our clinical cases had accumulated we noticed that it involved unignorable danger in patients of older ages and those with myocardial damage and with cyanosis. Therefore, for those cases the simple low body temperature method is not indicated, and they have to be handled by some other method.
(author's abstraet)

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