Cerebral microembolism during carotid endarterectomy

: This study was designed to assess the intraoperative risk of cerebral microembolism, as detected by transcranial Doppler ultrasonography, during carotid endarterectomy. : Thirty-six patients (37 procedures) with symptomatic (n = 35) or asymptomatic (n = 2) internal carotid artery origin stenosis (>50%) were monitored continuously during carotid endarterectomy. Special instrumentation was used to detect high-intensity transient signals (HITS) in the middle cerebral artery on the carotid endarterectomy side. All HITS satisfied a priori established criteria. : The incidence of carotid endarterectomies with formed-element HITS increased at clamp release (23/37, P<0.001) and shunt opening (7/11, P = 0.014), and during wound closure (13/22, P<0.005) and shunting (5/11, P = 0.046). HITS with air microbubble characteristics were detected at clamp release (22/37, P<0.001) and shunt opening (5/11, P = 0.025). : HITS do not occur randomly during carotid endarterectomy. Shunting, unclamping, and wound closure are high-risk periods.