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 preope rative CO2 cerebrovascular reactivity index (CO2 RI) with carotid and cereb ral angiography in predicting the risk of severe cerebral ischaemia (SCI) d uring carotid endarterectomy (CEA). Seventy-four consecutive patients sched uled 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 vo ltage and/or a fall in FV greater than or equal to 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 f all in FV greater than or equal to 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 percentag e stenosis of the contralateral ICA, and (3) the difference between ipsilat eral and contralateral CO2RI. Using these factors, a logistic regression mo del for predicting the risk of SCI was established which provided a sensiti vity 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 hemispher es. This information may assist in presurgical planning and help to select asymptomatic carotid lesions for surgery.