Cerebral Blood Flow Measurement by Near-Infrared Spectroscopy During Carotid Endarterectomy

Background: It is crucial to evaluate cerebral blood flow (CBF) during carotid endarterectomy (CEA). However, it is difficult to measure CBF in the operating room. The recent development of high-accuracy near-infrared spectroscopy (NIRS) has enabled the measurement of regional CBF following injection of indocyanine green (ICG). We aimed to measure changes in regional CBF by clamping the carotid artery during CEA and to analyze factors affecting the blood flow index (BFI) in CEA. Methods: Patients undergoing elective CEA were enrolled in this study after it was approved by the institutional ethical board. All patients underwent CEA under general anesthesia. Intraoperative blood pressure was controlled about 30% higher than the precarotid cross-clamping during carotid cross-clamping. ICG (0.5 mg/kg) was injected before, during, and after carotid cross-clamping. The kinetics of an intravenous bolus of ICG were monitored by a NIRS oximeter (NIRO200NX) and the BFI was calculated using the slope of the ICG concentration. The impact of carotid cross-clamping on the BFI was evaluated, along with factors influencing changes in the BFI. Results: A total of 50 patients were enrolled. The BFI significantly decreased during carotid cross-clamping compared with baseline values (from 0.077 +/- 0.019 to 0.0054 +/- 0.0019 mu mol/L/s) (P < 0.01). After unclamping the common carotid artery, the BFI recovered to the preclamping level (0.0073 +/- 0.0023 mu mol/L/s) (P < 0.01). Multiple logistic regression analysis revealed that abnormalities of the circle of Willis correlated significantly with reduced BFI (odds ratio = 12.07, P = 0.036). Conclusions: The BFI was significantly reduced by carotid artery clamping during CEA. Abnormalities of the circle of Willis were a significant factor contributing to reduced BFI.