NONINVASIVE MEASUREMENT OF REGIONAL CEREBRAL BLOOD-FLOW BY NEAR-INFRARED SPECTROSCOPY AND INDOCYANINE GREEN

Clinicians lack a practical method for measuring CBF rapidly, repeated ly, and noninvasively at the bedside. A new noninvasive technique for estimation of cerebral hemodynamics by use of near-infrared spectrosco py (NIRS) and an intravenously infused tracer dye is proposed. Kinetic s of the infrared tracer indocyanine green were monitored on the intac t skull in pigs. According to an algorithm derived from fluorescein fl owmetry, a relative blood flow index (BFI) was calculated. Data obtain ed were compared with cerebral and galeal blood flow values assessed b y radioactive microspheres under baseline conditions and during hemorr hagic shock and resuscitation. Blood flow index correlated significant ly (r(s) = 0.814, P < 0.001) with cortical blood flow but not with gal eal blood flow (r(s) = 0.258). However, limits of agreement between BF I and CBF are rather wide (+/- 38.2 +/- 6.4 mL 100 g(-1) min(-1)) and require further studies. Data presented demonstrate that detection of tracer kinetics in the cerebrovasculature by NIRS may serve as valuabl e tool for the noninvasive estimation of regional CBF. Indocyanine gre en dilution curves monitored noninvasively on the intact skull by NIRS reflect dye passage through the cerebral, not extracerebral, circulat ion.