DEVELOPMENT OF TRAUMATIC BRAIN EDEMA IN OLD VERSUS YOUNG-RATS

Age is an important factor of mortality and morbidity following trauma tic brain injury. The causes for the adverse effect of old age remain obscure. The aim of this study was to clarify whether age affects the development of posttraumatic brain edema. In Wistar rats, a cortical f reezing lesion was applied to the parietal region in ketamine-xylazine anesthesia. 18 young rats (4-6 months) were compared to 15 old animal s (36-40 months). In the early peritraumatic and late posttraumatic pe riod blood pressure was monitored. 24 hours after trauma, the brains w ere removed and hemispheric swelling, water- und electrolyte-contents were measured. In addition, the brains of 3 animals of each group were histologically evaluated. In the old age group, 3 animals died during the 24 hours observation period (mortality 20%), whereas all young ra ts survived (p < 0.01). The cortical freezing lesion resulted in a hem ispheric swelling of 6.9 +/- 0,5% in young, and 10.4 +/- 0.8% in old a nimals (p <0.001). Accordingly, the increase of cerebral water content due to the lesion was significantly more pronounced in the group of o ld rats, i.e. 2.05% in old versus 1.50% in young animals (p < 0.01). T he increase of swelling and edema in the old age group could not be at tributed to arterial hypertension. On the contrary, mean arterial bloo d pressure was significantly lower in old animals. Histological examin ations did not reveal significant differences between the two groups. Edema generation following a standardized cryogenic lesion is markedly enhanced in old versus young rats. This might be one factor among oth ers for higher mortality and morbidity following traumatic brain injur y in old versus young individuals.