Since one important determinant of CBF is perfusion pressure, it seems reasonable to assume that the distal arterial pressure in the ipsilateral hemisphere during carotid occlusion would provide some indication of collateral CBF. Stump pressure involves direct measurement of the retrograde internal carotid artery pressure following occlusion of the more proximal common and external carotid arteries. Stump pressures are neither sensitive nor specific. When stump pressure was compared to EEG monitoring, 6% of patients demonstrated ischemic EEG changes despite stump pressures in excess of 50 mmHg. On balance, extreme values (<25 mmHg or >60 mmHg) are useful indicators of the state of the cerebral circulation, but not intermediate values Anesthesiology refresher courses 2011