Pial Artery Pressure after One Hour of Global Ischemia

Abstract

Pial artery pressure was measured in anesthetized control cats and in animals subjected to 1 h of global ischemia and 6 h of recirculation. Cerebral blood flow (CBF) was measured with the intraarterial ¹³³Xe technique before and after ischemia, and lumped segmental resistances upstream and downstream to the pial artery were calculated. In the control brain, upstream resistance was 1.30 ± 0.28 and downstream resistance 0.94 ± 0.1 mm Hg ml-¹ 100 g min. During the postischemic hypoperfusion period, both resistances significantly increased, indicating that hypoperfusion constitutes a dysregulation of both large extracerebral and small intracerebral vessels. Hypercapnia induced an increase of CBF in the control brain and was accompanied by a fall in downstream resistance, demonstrating intracortical vasodilation. By contrast, hypercapnia did not provoke changes in either CBF or segmental resistances in the hypoperfusion period. In conclusion, during the postischemic hypoperfusion period, both extra- and intracortical resistances are increased and vascular reactivity to CO₂ is abolished.