NEAR-INFRARED MONITORING OF CEREBRAL OXYGENATION STATE DURING CAROTIDENDARTERECTOMY

BACKGROUND Recent studies have indicated that near-infrared spectrosco py (NIRS) could continuously and noninvasively observe the changes in cerebral oxygenation state during hypoxia and ischemia, using their op tical properties. Its validity and usefulness during cerebrovascular s urgery, however, still remain to be clarified. METHODS Using NIPS, we continuously monitored the changes in the concentration of oxyhemoglob in, deoxyhemoglobin, and total hemoglobin ([oxy-Hb], [deoxy-Hb], and [ total Hb], respectively) and redox state of cytochrome oxidase (cyt ox ) during carotid endarterectomy for 22 patients, and we compared the N IPS responses with those of intraoperative somatosensory evoked potent ials (SEP) and regional cerebral blood flow (rCBF). RESULTS In 9 of 22 patients, cross-clamping of the carotid artery caused a continuous de crease in [oxy-Hb] and [total Hb], and an increase in [deoxy-Hb]. Cyt ox was partially reduced during the clamping. These NIRS responses dem onstrated the occurrence of severe hypoxia in the ipsilateral cerebral tissue. These patients showed a marked decrease in the N-20 amplitude of SEP and rCBF. In contrast, the other 13 patients did not show a si gnificant decrease in the cerebral oxygenation state, which showed no remarkable changes in either SEP or in rCBF. CONCLUSIONS NIPS could su ccessfully judge the cerebral oxygenation state noninvasively during c arotid surgery and was more sensitive to ischemic crisis than other in direct methods.