Intraoperative transcranial Doppler sonography monitoring during carotid surgery under locoregional anaesthesia.
OBJECTIVE
Studies comparing transcranial Doppler ultrasonography (TCD) with other intraoperative monitoring techniques for detecting clamping ischaemia during carotid endarterectomy under general anaesthesia suggest that a reduction of > two-thirds in the mean middle cerebral artery velocity (mMCAv) or a reduction of > 0.4 in the preclamping mMCAv: clamping mMCAv ratio warrants cerebral protection. Our aim was to study the relationship between mMCAvs and clamping ischaemia during carotid endarterectomy in awake patients.


METHODS
In a consecutive series of 57 patients undergoing carotid endarterectomy under locoregional anaesthesia 51 were monitored by intraoperative TCD, continuous 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 mean 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 that four other patients (7.8%) should have been shunted. All four had significantly higher clamping mMCAvs than the five shunted patients (11.5 +/- 1.9 vs. 1.8 +/- 1.1, p = 0.0012).


CONCLUSIONS
Intraoperative TCD 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 unnecessary shunting due to false-positives.
Giannoni
M F
MF
I Cattedra di Chirurgia Vascolare, Università di Roma, La Sapienza, Italy.
Sbarigia
E
E
Panico
M A
MA
Speziale
F
F
Antonini
M
M
Maraglino
C
C
Fiorani
P
P
D000368:Aged; D000772:Anesthesia, Local; D001783:Blood Flow Velocity / Q000502:physiology; D001921:Brain / Q000000981:diagnostic imaging; D002343:Carotid Artery, Internal / Q000601:surgery; D016893:Carotid Stenosis / Q000175:diagnosis / Q000601:surgery*; D002536:Cerebral Arteries / Q000000981:diagnostic imaging*; D004569:Electroencephalography; D004691:Endarterectomy; D005260:Female; D006801:Humans; D007432:Intraoperative Period; D002546:Ischemic Attack, Transient / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D009407:Nerve Block; D011237:Predictive Value of Tests; D017585:Ultrasonography, Doppler, Transcranial