LAUSR

OBJECTIVE To evaluate and compare the efficacy of intraoperative neurophysiological monitoring (IONM) and intraoperative transcranial Doppler (TCD) techniques for identification of hypoperfusion during carotid artery (CA) clamp and hyperperfusion after release of occlusion during carotid endarterectomy (CEA). METHODS A retrospective, consecutive case series of 152 patients undergoing CEA between June 2018 and March 2020 were reviewed. Monitoring of somatosensory evoked potentials (SEPs), motor evoked potentials (MEPs), electroencephalogram (EEG) and TCD were investigated. RESULTS Three patient cohorts were observed after clamping CA: A, in 132 of the 152 patients (87%), TCD blood flow velocity decreased by less than 50%, and there were no changes in IONM; B, in 5 of 152 (3%) patients, TCD blood flow rate was reduced between 50% and 100% with no changes in IONM; C, in 15 patients (10%), blood flow velocity was reduced by 50% to 100%, and all IONM modalities met warning criteria. With increased blood pressure, IONM and blood flow velocities improved to less than warning criteria in 8/15 patients. In 6 of the 7 remaining patients, IONM modalities recovered to baseline immediately after clamps were removed from CA. The one patient with persistent MEP deterioration experienced a postoperative proximal muscle weakness which recovered 48 hours later. In 22 patients, TCD detected hyperperfusion at the moment of clamp release. CONCLUSIONS TCD blood flow velocity is correlated with MEP and SEP amplitude changes after clamping. After declamping, TCD can detect hyperperfusion and help to regulate blood pressure to prevent hyperperfusion.