Comparison of changes in cerebral blood flow and cerebral oxygen saturation measured by near infrared spectroscopy (NIRS) after acetazolamide

The present study compares the change of cerebral blood flow and HbO(2) measured by near-infrared spectroscopy (NIRS) after administration of 1000 mg acetazolamide intravenously. CBF studies in 21 patients with ischaemic cerebrovascular disease were per formed routinely with the (133)Xenon technique, Additionally the local HbO(2) was recorded by NTRS. A rest study was followed by a second study after the administration of 1000 mg acetazolamide. In 18 patients we observed an increase of 30.8% of CBF and 4.7% of HbO(2), 3 patients showed a decrease of CBF and 2 patients a simultaneous decrease of HbO(2). We did not find a correlation between the absolute values of CBF and HbO(2) at rest or after stimulation. However, a positive correlation (r=0.71, p <0.05) between the change of CBF and HbO(2) could be detected. Assuming a threshold value of normal CBF reactivity of 30% and 4% HbO(2) reactivity we found for NIRS a sensitivity of 0.88 and a specificity of 0.75. The results demonstrate that changes of CBF can be detected with NIRS and the algorithm of the used monitor is able to calculate the intracranial part of the signal. So, NIRS can be used as noninvasive screening method to test the cerebrovascular reserve capacity.