Abstract
Blood flow in the middle cerebral artery was monitored during carotid artery surgery under loco-regional anaesthesia by plexus block in awake patients in order to assess the value of transcranial pulsed Doppler in understanding the embolic or haemodynamic mechanisms of peroperative cerebrovascular accidents. Blood flow changes in the middle cerebral artery ipsilateral to the operated carotid artery were compared with clinical, paraclinical and operative findings. Sixty-two patients were included in the study, 34 with symptomatic carotid artery lesions and 28 with very severe, progressive but asymptomatic stenosis. Thirteen patients (9 with symptomatic and 4 with asymptomatic lesions) suffered one or more neurological events during surgery. The blood flow velocities were studied at different stages during surgery and compared between the two groups-symptomatic and asymptomatic to try and assess the mean systolic velocities predictive of cerebral hypoperfusion. Three events occurred during carotid artery dissection, 7 at clamping, 3 during clamping; 9 shunts were installed, one of which at the twelfth minute of clamping. A shunt was not installed in 4 cases : two events occurred at the end of the operation (muscle weakness, diplopia), one event occurred during an episode of hypotension, another at clamping which resulted in aborting the operation as transluminal pulsed Doppler suggested an embolism during dissection. Two events were attributed to an embolic phenomenon and 16 to cerebral hypoperfusion. Peroperative middle cerebral arterial flow recording enables detection of an embolism, monitoring of a shunt and the prediction of a neurological event should the mean systolic velocities fall to less than 15 cm/s and the reduction in velocity attain 70 % (sensitivity 87.5 %, specificity 91 %).