The Utility of Using the Bispectral Index—Vista for Detecting Cross-Clamping Decline in Cerebral Blood Flow Velocity

Abstract

Patients undergoing carotid endarterectomy for extracranial internal carotid artery stenosis are at risk of cerebral ischemia/hypoperfusion. Criterion recommended by European and American committees to determine whether to place a shunt consisted of a decline in transcranial Doppler ultrasonography-measured middle cerebral artery blood flow velocity (MCBFV) to < 30% to 40% of intraoperative preclamp value. To assess the discriminative power of the bispectral index (BIS)-Vista monitor for detecting a 40% decline in MCBFV with cross-clamping. In 20 patients undergoing carotid endarterectomy under remifentanil/propofol anesthesia, BIS-Vista data, MCBFV, and pulsatility index from bilaterally mounted BIS-Vista and transcranial Doppler monitors were continuously recorded. Coefficient of determination revealed good correlation (r = 0.763) between ipsilateral BIS-Vista and MCBFV after cross-clamping. BIS-Vista exhibited a high discriminative power of 0.850 (95% confidence interval, 0.455-0.966) area under the receiver-operating characteristic curve in detecting an ipsilateral 40% MCBFV decline. Two-way analysis of variance (location by time) suggests that BIS-Vista exhibited a global decline; ie, both BIS-Vistas declined when 1 carotid on either side was clamped because there was no significant interhemispheric difference (P = .112) in mean BIS-Vista values over time. Although we demonstrated good correlation and high discriminative power of the BIS-Vista monitor in depicting a MCBFV decline that could serve as indicator of decline in cerebral activity, BIS-Vista cannot be considered a reliable indicator of cerebral ischemia/hypoperfusion that could replace transcranial Doppler monitoring to determine whether a shunt is to be placed.