CLINICAL INVESTIGATIONS Differences in Vasodilatory Capacity and Changes in Cerebral Blood Flow Induced by Acetazolamide in Patients with Cerebrovascular

To investigate changes in cerebral blood flow (CBF) and blood volume induced by acetazolamide (ACZ) in patients with a vari-able autoregulatory status responding to reduced perfusion pressure, PET measurements of hemodynamic parameters were performed on patients with cerebrovascular disease, and the relationships between the parameters were evaluated. Methods: Sixteen patients with unilateral major cerebral arterial occlusive disease underwent PET studies with 15O-gas and the steady-state method to obtain hemodynamic parameters in the brain. All patients and 8 healthy volunteers underwent H215O PET at baseline and 10 min after ACZ injection to calculate the CBF and arterial-to-capillary blood volume (V0) based on a 2-compartment model. Results: The regional CBF (rCBF) and V0 increased significantly after ACZ administration in volunteers and in the hemisphere contralateral to the ischemic side in patients. However, in a subgroup of patients with disease who showed a significant reduction in the rCBF increase in the ipsilateral hemisphere, the ACZ challenge caused a decrease in the rCBF even though the V0 showed a significant increase. The reduction in the rCBF increase was associated with an asym-metric increase in oxygen extraction fraction (OEF) but not with an absolute OEF increase. Conclusion: The increases in rCBF and V0 induced by ACZ administration, as well as absolute OEF value in the baseline condition, did not necessarily parallel each other in the ipsilateral hemispheres of patients. Thus, the in-crease in rCBF after ACZ challenge may not represent vasodi-latory capacity in patients with cerebrovascular disease, espe-cially in the regions with a reduced rCBF response. Key Words: acetazolamide; cerebrovascular disease; cerebral blood flow; vasodilatory capacity; cerebral blood volum