Cerebrovascular resistance in ischemia.

The cerebrovascular resistance (CVR) of rat, and its dependence on stagnant blood or endothelial capillary swelling, was studied after 10 min of total ischemia by 10 s single carotid infusion of [14C]butanol in saline. The regional saline flow (CPR) was calculated from the uptake of [14 C]butanol. CVR was estimated at infusion pressures ranging from 8--25 kPa (60--190 mm Hg). At 14.7 kPa (110 mm Hg) infusion pressure, the regional CVR of the non-ischemic group varied between 0.21 and 0.40 kPa 100 g min ml-1. After 10 min of complete global cerebral ischemia, it increased to values between 0.82 and 1.95. Removal of blood from the brain by rinsing prior to ischemia did not change the CVR in ischemia. Increasing the plasma osmolality by 8% with mannitol before ischemia attenuated the CVR increase in ischemia. Thus, although osmotic swelling of endothelial cells contributed, the main cause of the CVR increase in ischemia was constriction of arterioles.