Effects of Alpha Adrenergic Blockade on Autoregulation and Chemical Vasomotor Control of CBF in Stroke

Autoregulation and chemical vasomotor control of cerebral blood flow (CBF) were quantitatively tested in 19 patients with various types and sites of cerebral ischemia and infarction. The effect of alpha adrenergic blockade of cerebral vessels by phenoxybenzamine (PBZ) also was evaluated in more than half of the patients. No correlation was found between the degree of cerebral dysautoregulation and impairment of chemical vasomotor control of CBF. Patients with brainstem ischemia and infarction showed normal vasomotor reactivity of CBF to changes in PaCO2, despite the impairment of cerebral autoregulation during both induced hypotension and hyper ension. Following intracarotid injection of 10 mg PBZ, the degree of cerebral dysautoregulation lessened during induced hypotension but increased during induced hypertension. Chemical vasomotor control of CBF in response to changes in PCO2, was not significantly altered by the PBZ injection. Changes in autoregulation index (a quantitative measure of cerebral autore...