Abstract
The observation has been made by several investigators that the young animal is much less susceptible to asphyxia than the adult. 1 , 2
No information has been available, however, concerning the essential factors involved in the greater resistance of the young to asphyxia. It was of interest, therefore, to determine whether the brain itself is more resistant to anoxia and accumulation of metabolites in the young animal. This question has been investigated by comparing the effects of complete arrest of the cephalic circulation for various periods of time in adult dogs and in puppies. The method which has been employed to produce sudden complete stasis of blood in the head by means of a pressure cuff in the cervical region has been described 3 as has also the effects of this procedure on adult animals. 4
The adult dog rarely recovers consciousness after 8 minutes of complete vascular occlusion. It remains comatose as long as it lives, losing all sensation and retaining only very primitive responses on the reflex level. After 6 minutes of vascular stasis, consciousness is recovered in 24 to 48 hours as a rule and following this, the animal is very severely ataxic, restoration to normal requiring a period of weeks or months. Following 4 minutes of arrest of the cephalic circulation, consciousness returns in 18 to 24 hours and the residual ataxic symptoms, though somewhat less severe, are still present. After only 2 minutes of vascular occlusion, slight ataxia persists for a week or more.
Complete arrest of the cephalic circulation was produced in 8 puppies using the same technic as had been employed in the study of adult animals. The results of temporary cessation of the brain circulation in these animals are in striking contrast to the effects of the procedure in the adult.
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