Correlation of Cerebral Oximetry Measurement with Carotid Artery Stump Pressures During Carotid Endarterectomy

Cerebral oximetry and internal carotid artery stump pressures were measured during carotid endarterectomy to assess whether cerebral oximetry could be used as a noninvasive and reliable alternative to monitor cerebral blood flow and the need for selective carotid artery shunting. Carotid endarterectomy procedures were performed in 27 patients wherein a cerebral oximeter was placed on the ipsilateral forehead preoperatively. Stump pressure data as well as cerebral oximetry readings at baseline and before and after carotid artery clamping were gathered. The differences between baseline and clamped carotid artery oximetry readings were calculated for each subject and divided by the baseline reading to provide an adjusted measure of percent oximetry change. This normalized percent change in cerebral oximetry readings was then correlated with stump pressure. Carotid artery stump pressures correlated closely with the normalized change in cerebral oximetry readings (r = -0.57, p = 0.002). Based on the regression analysis, stump pressure readings of 50 and 25 mm Hg were predicted by at least a 15% and 30% drop in cerebral oximetry readings, respectively. Based on low intraoperative stump pressure and changes in cerebral oximetry readings, arterial shunt placement was used in eight patients. There was no morbidity or mortality from the 27 carotid endarterectomy procedures performed. Carotid endarterectomy can be performed safely with cerebral oximetry as a simple, noninvasive, and reliable alternative to internal carotid artery stump pressure measurements in determining the need for selective carotid artery shunting.