EEG monitoring during carotid endarterectomy.

One hundred and thirty-one patients undergoing 142 carotid endarterectomy procedures were randomized to have their operation performed either with or without intra-operative electroencephalographic (EEG) monitoring. Patients with EEG monitoring were shunted if both the internal carotid back pressure (ICBP) was less than 50 mmHg and ipsilateral change was evident on the EEG after clamping. Patients without EEG monitoring were shunted if ICBP was less than 50 mmHg. There one postoperative death (0.7%) with neurological deficits occurring in five patients (3.5%). There were significantly fewer neurological deficits (P = 0.02) in patients with no EEG change (one of 59) compared with those with EEG change (two of 13). There was a highly significant increase (P = 0.005) in incidence of neurological deficit (two of five patients) when ICBP was considered 'adequate' at 50 mmHg or greater but EEG change occurred. No neurological deficit occurred in 14 patients who were not shunted with ICBP less than 50 mmHg but with no EEG change. There was no difference in the incidence of neurological deficit in patients with low and high ICBP when both 50 and 55 mmHg were used as the cut-off points. It is concluded that EEG monitoring is useful in identifying patients requiring shunting during carotid endarterectomy. Use of a shunt is recommended if there is EEG change regardless of ICBP; conversely, if ICBP is low but there is no EEG change it would appear safe to proceed without shunting.