The value of electroencephalography and ocular pneumoplethysmography in carotid shunting

To investigate whether it is possible to detect in a non-invasive way those patients who undergo carotid surgery under general anesthesia and do not tolerate carotid clamping without EEG changes, preoperative EEG and OPG carotid compression tests were compared with the results of intraoperative carotid clamping and EEG control. Eleven of 126 patients (8.7%) who were studied had EEG changes after carotid clamping. They also had preoperatively either EEG changes or a Collateral Ophthalmic Artery Pressure, as measured with OPG compression tests, lower than 30 mm Hg, or both criteria. However, preoperative positive criteria for EEG and OPG were also seen in patients who had no EEG changes during intraoperative carotid clamping. Therefore these non-invasive tests can select those patients who will need a shunt (sensitivity 100%), but according to those methods too many patients will be shunted (specificity 76%).