PHYSIOLOGICAL DETERMINATION OF CEREBROVASCULAR RESERVES AND ITS USE IN CLINICAL MANAGEMENT

Cerebrovascular reserve (CVR) can be assessed by measuring the hemodyn amic response to a physiological stress such as alteration of blood pr essure, increase in tissue acidosis, lowered oxygen supply, increase i n metabolic demand, or occlusion of an artery. Failure of the cerebrov ascular system to maintain function or normative values of several int errelated hemodynamic variables-cerebral blood flow (CBF), oxygen extr action fraction (OEF), cerebral blood volume (CBV), and cerebral metab olic rate of oxygen (CMRO(2)),-in response to a stress implies a compr omise of the normally robust compensatory mechanisms. The conclusions that are possible from this information depend on the type of stress i nduced and the technology used to measure the response. Technologies t hat permit a rapid test-retest format coupled with a physiological str ess provide the most direct information about the hemodynamics of cere brovascular territories. Patients whose cerebral vasculature becomes c ompromised by any of a broad range of disorders and who, thus, are at increased risk for stroke now can be readily identified based upon evi dence of exhausted CVR. Strategies for treating hemodynamically driven disorders also can now be designed based upon such patient-specific C VR information. It is hoped that integration of CVR into the standard clinical assessment of patients with occlusive vascular disorders (OVD ) will lead to treatments that focus not only on the previously unders tood embolic causes of stroke, but also on the often interrelated hemo dynamic factors.