Correlation of cerebral blood flow and MCA flow velocity measured in healthy volunteers during acetazolamide and CO2 stimulation.

The assessment of the cerebrovascular reserve capacity (RC) has become a widely used tool in the management of cerebrovascular disease. Discrepancies become obvious, however, if results obtained with different methods are compared. Aim of the present study, therefore, was to compare blood velocity and cerebral perfusion data in the same group of healthy test persons. In 32 volunteers regional cerebral blood flow (rCBF) was measured with the 133Xe-inhalation method. F1 as grey matter flow and the initial slope index (ISI) were computed. Simultaneously flow velocity in the middle cerebral artery (VMCA) was assessed by transcranial Doppler sonography (TCD). Measurements were performed in the resting state, during inhalation of 7% CO2 and after 1 g acetazolamide. Baseline VMCA was 62.38 +/- 16.1 cm/s, 90.84 +/- 23.85 cm/s during hypercapnia and 84.91 +/- 24.54 cm/s after acetazolamide. There was no significant change of baseline or stimulated values with age. F1 rose from baseline 76.25 +/- 12.48 ml/100 g/min to 103.90 +/- 14.6 ml/100 g/min in hypercapnia and to 98.4 +/- 14.9 ml/100 g/min after acetazolamide. The baseline F1 values and the response to CO2 decreased with age (p = 0.01) whereas for the acetazolamide reaction an age dependency could not be proven. ISI baseline values (41.5 +/- 6.1 ml/100 g/min) as well as those found after CO2 or acetazolamide decreased significantly with age. In hypercapnia changes of F1 and ISI were not too well related with changes of VMCA (F1: r = 0.599; ISI: r = 0.473), but better during acetazolamide exposure (F1: r4 = 0.715; ISI: r = 0.522). The age dependency of resting and stimulated values has to be considered when assessing the reserve capacity. There is a correlation between changes of the perfusion and flow parameters in healthy individuals which, however, may be worse in cerebrovascular disease.