Abstract
Histopathological and succinic acid dehydrogenase (SAD) activity changes, and the electron spin resonance (ESR) were examined in the brains of dogs exposed to various hypothermic conditions. A simple hypothermic cardiac arrest of 5 min duration occurred in the group subjected to 28 degrees C, and normal SAD activity was noted in dogs exposed 1-hour extracorporeal circulation under normothermia. In cases of a hypothermia below 28 degrees C, a decrease in enzyme activity, marked histopathological changes and the disappearance of the ESR signal were observed. In dogs killed immediately after induction of 20 degrees C hypothermia, the histopathological changes were primarily ischemic in nature, while in dogs killed at 1-12 month intervals after the experiments, irreversible gliosis was dominant. Our findings suggest that, to avoid brain damage under conditions of deep hypothermic circulatory arrest, the critical range is between 26-28 degrees C for rectal, and approximately 28-30 degrees C for brain temperature.
Published Version
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