BIPHASIC EDEMA DEVELOPMENT AFTER EXPERIMENTAL BRAIN CONTUSION IN RAT

The time course of edema development following experimental brain cont usion was studied by measuring cortex specific gravity 1 and 12 h afte r the trauma, and thereafter once daily until 7 days after the trauma. A biphasic development of edema was observed; the specific gravity de creased to a minimum on day 2 (P < 0.001), increased to an almost norm al level on day 4 and thereafter decreased again to a second minimum 6 days after the trauma (P < 0.01). Delayed edema formation has been re cognized in clinical settings, but has not been described in experimen tal studies. This study, with a prolonged daily follow-up, clearly dem onstrates that a secondary phase of edema is an experimentally reprodu cible entity. The model will enable study of the pathogenetic mechanis ms.