INTRAOPERATIVE TRANSCRANIAL DOPPLER SONOGRAPHY MONITORING DURING CAROTID SURGERY UNDER LOCOREGIONAL ANESTHESIA

Objectives: Studies comparing transcranial Doppler ultrasonography (TC D) with other intraoperative monitoring techniques for detecting clamp ing ischaemia during carotid endarterectomy under general anaesthesia suggest that a reduction of > two-thirds in the mean middle cerebral a rtery velocity (mMCAv) or a reduction of > 0.4 in the preclamping mMCA v: clamping mMCAv ratio warrants cerebral protection. Our aim was to s tudy the relationship between mMCAvs and clamping ischaemia during car otid endarterectomy in awake patients. Materials and methods: In a con secutive series of 57 patients undergoing carotid endarterectomy under locoregional anaesthesia 51 were monitored by intraoperative TCD, con tinuous EEG, and neurologic awake testing. Results: Five of the 51 (9. 8%) patients had transient clamping ischaemia, which carotid shunting reversed. TCD showed that these five patients had significant lower me an mMCAvs than the other 46 patients, who had no deficits (1.8 +/- 1.1 cm/s vs. 26.2 +/- 8.5, p = 0.0003). Current TCD criteria indicated th at four other patients (7.8%) should have been shunted. All four had s ignificantly higher clamping mMCAvs than the Jive shunted patients (11 .5 +/- 1.9 vs. 1.8 +/-: 1.1, p = 0.0012).Conclusions: Intraoperative T CD detected cerebral ischaemia and yielded no false-negative. An mMCAv of 10 cm/s or less may indicate the risk of clamping ischaemia better than the higher threshold currently proposed. This would avoid unnece ssary shunting due to false-positives.