• acetazolamide;
  • blood flow index;
  • cerebral blood flow;
  • indocyanine green;
  • near-infrared spectroscopy;
  • single photon emission computer tomography

Background and purpose:  It is important to find a reliable and bedside method, which can estimate the cerebral blood flow (CBF) of patients in clinical settings. Estimation of CBF by calculating a blood flow index (BFI) using continuous wave near-infrared spectroscopy (CW-NIRS) and indocyanine green (ICG) as an iv tracer has been proposed to be a feasible and promising method. To validate if the BFI method can detect relative changes in CBF we compared data with the established method 133Xenon single photon emission computer tomography (133Xe-SPECT).

Methods:  Ten healthy subjects were investigated before and after a bolus of acetazolamide. NIRS data were obtained using a multi source detector separation configuration in order to assess a corrected BFI (BFIcorr) value, which attempts to eliminate contamination of skin blood flow.

Results:  Data obtained showed no significant correlation between CBF changes measured by 133Xe-SPECT and BFIcorr (0.133, = 0.732). After acetazolamide, a 49% increase in CBF was detected using the 133Xe-SPECT method, whereas no changes in any ICG variables were observed after acetazolamide.

Conclusion:  The study shows that it is not possible to obtain reliable BFI data, which reflect changes in CBF after acetazolamide infusion, using the CW-NIRS and ICG method.