A clinical evaluation of near-infrared cerebral oximetry in the awake patient to monitor cerebral perfusion during carotid endarterectomy

Abstract

Study Objective To evaluate the relationship between continuous noninvasive monitoring of cerebral saturation (regional cerebral oxygen saturation [rS o 2]) and occurrence of clinical and electroencephalographic (EEG) signs of cerebral ischemia during carotid cross-clamping. Design Prospective clinical study. Setting University hospital. Patients Fifty ASA physical status II and III inpatients undergoing elective carotid endarterectomy with a cervical plexus block. Interventions rS o 2 was continuously monitored throughout surgery, while an independent neurologist evaluated the occurrence of both clinical and EEG signs of cerebral ischemia induced during carotid cross-clamping. Measurements and Main Results rS o 2 was recorded 1 and 3 minutes after clamping the carotid artery during a 3-minute clamping test. In 5 patients (10%), the carotid clamping test was associated with the occurrence of clinical and EEG signs of cerebral ischemia. All these patients were treated with the placement of a Javid shunt, which completely resolved the symptoms. In no patient was permanent neurological injury reported at hospital discharge. In 4 of these patients, EEG signs of cerebral ischemia were present at both observation times, and in one of them, the duration of cerebral ischemia was less than 2 minutes. The percentage rS o 2 reduction from baseline during the carotid clamping test was 17% ± 4% in patients requiring shunt placement and only 8% ± 6% in those who did not require it ( P = .01). A decrease in rS o 2 15% or greater during the carotid clamping test was associated with a 20-fold increase in the odd for developing severe cerebral ischemia (odds ratio, 20; 95% confidence interval, 6.7-59.2) ( P = .001); however, this threshold had a 44% sensitivity and 82% specificity, with only 94% negative predictive value. Conclusions Continuous rS o 2 monitoring is a simple and noninvasive method that correlates with the development of clinical and EEG signs of cerebral ischemia during carotid cross-clamping; however, we could not identify an rS o 2 threshold that can be used alone to predict the need for shunt placement because of the low sensitivity and specificity.