BACKGROUND AND PURPOSE: Induced hypothermia holds promise as an effective neuroprotective strategy following cerebral ischemia. The effect of mild hypothermia on cerebral hemodynamics is not well known. The authors investigated the influence of brain temperature on middle cerebral artery (MCA) mean flow velocity (MCA FV) and pulsatility index (MCA PI) in nonintubated, healthy volunteers undergoing mild induced hypothermia. METHODS: Mild hypothermia (target tympanic membrane temperature [T tym] degrees C) was induced in subjects using the Arctic Sun Temperature Management System (Medivance, Inc, Louisville, CO). MCA FV and MCA PI were recorded bilaterally with a 2 MHz pulsed probe every 30 minutes via the transtemporal window. RESULTS: Eighteen subjects (8 males, 10 females) 32 +/- 8 years of age were studied. Multivariate analysis indicated that MCA FV increased with increasing change in temperature (baseline tympanic temperature-tympanic temperature [DeltaT tym]) (P