Significance of resting and stimulated cerebral blood flow for predicting the risk of hemodynamic cerebral ischemia in a model of chronic hemodynamicinsufficiency

OBJECTIVE: It has been postulated that patients with a compromised cerebrov ascular reserve capacity (RC), defined as cerebral blood flow (CBF) respons e to acetazolamide (ACZ) (by percent), are at higher risk for ischemic stro ke. The value of CBF and RC for predicting the risk of hemodynamically indu ced impairment of cerebral function is examined. METHODS: Both common carotid arteries were occluded in 22 Wistar-Kyoto rats . Thirty-one days later, mean arterial blood pressure was reduced to 40 mm Hg for 30 minutes. Laser Doppler scanning of CBF at resting conditions and after intraperitoneal administration of ACZ (0.1 mg/g body weight) was perf ormed 30 minutes and 28 days after occlusion as well as before and during h ypotension. Memory and motor functions were examined before and after CBF m easurements. RESULTS: After occlusion, CBF dropped significantly and ACZ did not increas e CBF. Four weeks later, resting CBF had significantly improved but remaine d impaired, as did RC, showing a distinct interindividual variability. Hypo tension reduced CBF by 57 +/- 4% (P < 0.001) and significantly impaired mem ory and motor functions. CBF during hypotension correlated with vesting CBF before hypotension (r = 0.495, P = 0.027) and with CBF before (r = 0.392, P = 0.048) and after (r = 0.476, P = 0.034) ACZ, as determined 4 weeks afte r occlusion. There was no correlation with RC (r = 0.091, P = 0.702). Neuro logical tests performed 1 day after hypotension correlated with CBF during hypotension (memory function, P = 0.03; motor function, P = 0.02) but not w ith RC. CONCLUSION: In this model of chronic hemodynamic insufficiency, the risk of impairment to global cerebral function was predicted by resting CBF and CB F after ACZ but not by RC determined with ACZ.