Background: This study aimed to determine the effects of alveolar recruitment maneuver (RM) on cerebral oxygen saturation and cerebral blood velocity in patients undergoing carotid endarterectomy (CEA) before clamping of the carotid artery. Material/Methods: In this crossover exploratory study, all patients were randomized to undergo an RM (30 cmH2O of continuous airway pressure for 30 s) and a "sham" maneuver (SM; 5 cmH2O for 30 s), followed by an alternative intervention after a 5-min equilibration period. Near-infrared spectroscopy (NIRS) was used to monitor regional cerebral oxygen saturation (rSO2), and transcranial Doppler ultrasonography (TCD) to evaluate blood velocity of the middle cerebral artery (V-MCA). Changes in rSO2, V-MCA, mean arterial pressure (MAP), and heart rate (HR) in response to the 2 interventions were compared. Results: A total of 59 patients underwent the study procedure. RM reduced rSO2, V-MCA, MAP, and HR, but these variables slightly changed during SM. A significant drop in rSO2 was observed immediately after RM compared with the baseline value (68.51±4.4% vs 64.12±5.15%; P<0.001). The decrease in rSO2 was higher during the RM than during the SM (-6±4% vs 1±2%; P<0.001). Similarly, change in V-MCA was more significant in response to RM than SM (-26±19% vs 19±16%; P<0.001). The V-MCA value changed from 39 cm/s to 29 cm/s after RM. In addition, V-MCA of the ipsilateral to the surgical side decreased more obviously than the contralateral side (-26±19% vs -20±17%; P=0.001). Conclusions: An RM at 30 cmH2O of continuous airway pressure for 30 s decreased rSO2 and V-MCA. In addition, MAP and HR were affected. © 2021 International Scientific Information, Inc.. All rights reserved.