Prediction of cerebral ischaemia during carotid endarterectomy with preoperative CO2-reactivity studies and angiography.

The objective of this study was to assess the value of combining the preoperative CO2 cerebrovascular reactivity index (CO2RI) with carotid and cerebral angiography in predicting the risk of severe cerebral ischaemia (SCI) during carotid endarterectomy (CEA). Seventy-four consecutive patients scheduled for CEA underwent preoperative digital subtraction angiography and CO2-reactivity tests. During CEA, cerebral function monitor (CFM) was used to document cortical electrical activity, whilst transcranial Doppler measured the middle cerebral artery flow velocity (FV). A persistent fall in CFM voltage and/or a fall in FV > or = 60% on internal carotid artery (ICA) clamping were used as criteria for defining SCI. Complete data from 59 patients were obtained for final analysis. Twelve cases showed a fall in FV > or = 60%; 11 of these also showed a sustained fall in CFM voltage. Using logistic regression, the risk of SCI was found to be negatively associated with (1) contralateral CO2RI, (2) the percentage stenosis of the contralateral ICA, and (3) the difference between ipsilateral and contralateral CO2RI. Using these factors, a logistic regression model for predicting the risk of SCI was established which provided a sensitivity of 75% and specificity of 100%. The risk of SCI during CEA was related to the contralateral ICA stenosis and the CO2RI of both cerebral hemispheres. This information may assist in presurgical planning and help to select asymptomatic carotid lesions for surgery.