AbstractMicrovascular surgical techniques have made possible the improvement of cerebral blood flow, as demonstrated by angiography and by regional cerebral blood flow research. In this study, simultaneous mass spectrometer determinations of brain tissue and blood PO2, and pCO2, levels were used to evaluate the effectiveness of common carotid‐supraclinoid carotid anastomoses (CC‐SCA) in dogs. With blood pCO2maintained at a constant level, the baseline brain tissue pO2and pCO2levels were recorded. During the CC‐SCA procedure, which involved brain retraction and temporary vascular occlusion, brain tissue pO2levels fell to 40% of baseline and pCO2levels rose by 35%. Following restoration of flow via the anastomosis, the brain tissue pO2and pCO2levels agina reached bas