Microregional blood flow changes in experimental cerebral ischemia

Abstract

✓ A branch of the middle cerebral artery on the convexity of the dog brain was occluded to produce an area of focal cerebral ischemia which could then be defined by fluorescein angiography of the brain. Repeated fluorescein angiography and measurement of microregional cerebral blood flow by xenon133 injected into the carotid artery and monitored by miniature lithium-drifted silicon detectors for gamma activity demonstrated that the ischemic zone was reduced in size by better collateral flow when the animals were allowed to breathe 5% carbon dioxide and 95% oxygen. Conversely, hyperventilation reducing the pCO2 made the ischemic zone larger by reducing collateral flow. No evidence was found to indicate that hypercapnia preferentially deprived the ischemic zone of perfusion flow. Retrograde collateral flow in the surface arteries appeared effective in terms of microcirculatory perfusion.