Effects of hypothermia on intracranial pressure and brain edema formation: studies in a rat acute subdural hematoma model.

Acute subdural hematoma (SDH) is the most common mass lesion in severe head injury, and brain ischemia is the leading pathophysiological mechanism in the development of secondary brain damage following SDH. Hypothermia has been employed as an effective neuroprotective procedure in clinical and laboratory studies on cerebral ischemic and contusional injuries. In the present study, we used a rat acute SDH model to assess the effect of hypothermia on the intracranial pressure (ICP) and also on the brain edema formation at 4 h after hematoma induction. Mild (34 degrees C) and moderate (32 degrees C) hypothermia did not significantly affect the ICP or cerebral perfusion pressure, but they were associated with a significant lower cortical brain edema formation beneath the hematoma (81.09 +/- 0.49%, p<0.05; and 80.88 +/- 0.17%, p<0.01) when compared with the normothermic control group (81.65 +/- 0.52%). This reduction in brain edema formation was comparable to the results of MK-801 treatment (80.95 +/- 0.35%, p<0.01). The present findings indicate that hypothermia represents a potent neuroprotective strategy. The possible protective mechanisms of hypothermic protection afforded in this rat acute SDH model are discussed.