Time course of acetazolamide effect in normal persons.

The intravenous injection of the carbonic anhydrase inhibitor acetazolamide causes a sustained increase of blood flow velocity in the middle cerebral artery. This effect is used in the acetazolamide test of the so-called cerebrovascular reserve capacity. The acetazolamide test is performed routinely as a two-point measurement of the blood flow velocity by transcranial Doppler before and 15 to 20 minutes after drug injection. Based on the assumption that evaluation of the time course will more sensitively detect an impaired cerebrovascular reserve capacity, suitable parameters for description of the time course were developed and normal values were established from 18 healthy persons (31 hemispheres). The mean value for the maximal increase of the mean flow velocity (MFV) was 29.7 +/- 8.3 cm/sec (as percentage of increase, 62.0 +/- 17.3%) and the time of the maximal increase was 15.35 +/- 8.46 seconds. Also calculated were the velocity of the MFV rise to the maximal value (3.0 +/- 3.2 cm/sec/min), the mean of the changes of the continuously measured MFV to the baseline value (21.0 +/- 7.4 cm/sec), and the integral of MFV represented by the plane under the MFV curve (967.8 +/- 350.0 cm). The best parameter for the description of the time dependency of the acetazolamide effect is the integral of MFV.