Treatment window for hypothermia in brain injury

Object. The goal of this study was to evaluate the therapeutic window for h ypothermia treatment following experimental brain injury by measuring edema formation and functional outcome. Methods. Traumatic brain injury (TBI) was produced in anesthetized rats by using cortical impact injury. Edema was measured in the ipsilateral and con tralateral hemispheres by subtracting dry weight from wet weight, and neuro logical function was assessed using a battery of behavioral tests 24 hours after TBI In injured rats, it was found that brain water levels were elevat ed at I hour postinjury, compared with those in sham-injured control animal s, and that edema peaked at 24 hours and remained elevated for 4 days. Hypo thermia (3 hours at 30 degreesC) induced either immediately after TBI or 60 minutes after TBI significantly reduced early neurological deficits. Delay of treatment by 90 or 120 minutes postinjury did not result in this neurol ogical protection. Immediate administration of hypothermia also significant ly decreased the peak magnitude of edema at 24 hours and 48 hours postinjur y, compared with that in normothermic injured control animals. When delayed by 90 minutes, hypothermia did not affect the pattern of edema formation. Conclusions. When hypothermia was administered immediately or 60 minutes af ter TBI, injured rats showed an improvement in functional outcome and a dec rease in edema. Delayed hypothermia treatment had no effect on functional o utcome or on edema.