Effects of hypothermia on intracranial hemodynamics and ischemic brain damage-studies in the rat acute subdural hematoma model

Brain ischemia is the leading pathophysiological mechanism in the development of secondary brain damage after subdural hematoma (SDH). Hypothermia has been used as the effective neuroprotective treatment in clinical and laboratory studies of ischemic brain injury. In this study, we have examined the rat acute SDH model to assess the effect of hypothermia upon intracranial hemodynamics and also upon ischemic brain injury 4 hours after the induction of hematoma. Moderate hypothermia (32 degreesC) did not affect the intracranial pressure nor cerebral perfusion pressure, and it significantly reduced cortical brain edema formation underneath the hematoma (80.88 +/- 0.17%; p < 0.01) compared with the normothermic control group (81.65 +/- 0.52%). This reduction in brain edema formation was comparable to the result of MK-801 (2 mg/kg) treatment (80.95 +/- 0.35%; p < 0.01). Ischemic brain damage detected by H-E staining was also significantly reduced in the hypothermia and MK-801 treated groups (59.1 +/- 12.3 mm(3) and 66.4 +/- 13.8 mm(3); p < 0.01 and p < 0.05) compared with the normothermic control group (86.6 +/- 20.7 mm(3)). In conclusion, the present study demonstrates that hypothermia is a potent neuroprotective method and an inhibition of the glutamate excitotoxic process may contribute the protective mechanism of hypothermia in this rat acute SDH model.