Short-duration hypothermia after ischemic stroke prevents delayed intracranial pressure rise

Background: Intracranial pressure elevation, peaking three to seven post-stroke is well recognized following large strokes. Data following small-moderate stroke are limited. Therapeutic hypothermia improves outcome after cardiac arrest, is strongly neuroprotective in experimental stroke, and is under clinical trial in stroke. Hypothermia lowers elevated intracranial pressure; however, rebound intracranial pressure elevation and neurological deterioration may occur during rewarming. Hypotheses: (1) Intracranial pressure increases 24h after moderate and small strokes. (2) Short-duration hypothermia-rewarming, instituted before intracranial pressure elevation, prevents this 24h intracranial pressure elevation. Methods: Long-Evans rats with two hour middle cerebral artery occlusion or outbred Wistar rats with three hour middle cerebral artery occlusion had intracranial pressure measured at baseline and 24h. Wistars were randomized to 2·5h hypothermia (32·5°C) or normothermia, commencing 1h after stroke. Results: In Long-Evans rats (n=5), intracranial pressure increased from 10·9±4·6mmHg at baseline to 32·4±11·4mmHg at 24h, infarct volume was 84·3±15·9mm3. In normothermic Wistars (n=10), intracranial pressure increased from 6·7±2·3mmHg to 31·6±9·3mmHg, infarct volume was 31·3±18·4mm3. In hypothermia-treated Wistars (n=10), 24h intracranial pressure did not increase (7·0±2·8mmHg, P<0·001 vs. normothermia), and infarct volume was smaller (15·4±11·8mm3, P<0·05). Conclusions: We saw major intracranial pressure elevation 24h after stroke in two rat strains, even after small strokes. Short-duration hypothermia prevented the intracranial pressure rise, an effect sustained for at least 18h after rewarming. The findings have potentially important implications for design of future clinical trials. © 2013 World Stroke Organization.