Near-infrared spectroscopy extended with indocyanine green dye dilution for cerebral blood flow measurement: Median values in healthy volunteers

The cerebral blood flow (CBF) is an important vital parameter in neurointensive care. Currently, there is no non-invasive method for its measurement that can easily be applied at the bedside. A new tool to determine CBF is based on near-infrared spectroscopy (NIRS) applied together with indocyanine green (ICG) dye dilution. From a bilateral measurement on selected regions on the head of infrared (IR) absorption at various wavelengths during the dilution maneuver, the vascular perfusion characteristics of the two brain hemispheres can be determined in terms of mean transit time (mtt) of ICG, cerebral blood volume (CBV) and CBF. So far, on nine healthy volunteers, NIRS ICG dye dilution bihemispheric measurements were performed, which yielded to mtt given as median (range) of 9.3 s (5.1–16.3 s), CBV of 3.5 ml/100 g (1.7–4.1 ml/100 g), and CBF of 18.2 ml/(100 g×min) 11.1–48.6 ml/(100 g×min)]. Additionally, the blood flow index (BFI) was calculated with BFI= 13.8 mg/(100 g×s) 6.6–15.2 mg/(100 g×s)]. The Spearman rank correlation coefficient between CBF and BFI was R_S = 0.76. However, as the Bland & Altman plot between CBFNIRS and the CBF_BFI documents, the limits of agreement are rather wide (21.9±6.7). Under physiological conditions in healthy volunteers, no differences could be detected between the hemispheres.