Effects of acetazolamide on cerebral blood flow, blood volume, and oxygen metabolism: A positron emission tomography study with healthy volunteers

To evaluate changes in cerebral hemodynamics and metabolism induced by acet azolamide in healthy subjects, positron emission tomography studies for mea surement of cerebral perfusion and oxygen consumption were performed. Sixte en healthy volunteers underwent positron emission tomography studies with O -15-gas and water before and after intravenous administration of acetazolam ide. Dynamic positron emission tomography data were acquired after bolus in jection of (H2O)-O-15 and bolus inhalation of O-15(2). Cerebral blood flow, metabolic rate of oxygen, and arterial-to-capillary blood volume images we re calculated using the three-weighted integral method. The images of cereb ral blood volume were calculated using the bolus inhalation technique of (C O)-O-15 The scans for cerebral blood flow and volume and metabolic rate of oxygen after acetazolamide challenge were per-formed at 10, 20, and 30 minu tes after drug injection. The parametric images obtained under the two cond itions at baseline and after acetazolamide administration were compared. Th e global and regional values for cerebral blood flow and volume and arteria l-to-capillary blood volume increased significantly after acetazolamide adm inistration compared with the baseline condition, whereas no difference in metabolic rate of oxygen was observed. Acetazolamide-induced increases in b oth blood flow and volume in the normal brain occurred as a vasodilatory re action of functioning vessels. The increase in arterial-to-capillary blood volume made the major contribution to the cerebral blood volume increase, i ndicating that the raise in cerebral blood flow during the acetazolamide ch allenge is closely related to arterial-to-capillary vasomotor responsivenes s.