Case Report Abrupt Suppression of Electroencephalographic Activity Due to Acute Hypercapnic Event Under Cardiopulmonary Bypass Detected by the NeuroSENSE Depth-of-Anesthesia Monitor Guillaume Lemaire, MD * ,1 , Romain Courcelle, MD * , Emiliano Navarra, MD y , Mona Momeni, MD, PhD * * Department of Anesthesiology, Cliniques Universitaires Saint-Luc, Universit  e Catholique de Louvain, Brus- sels, Belgium y Department of Cardiothoracic and Vascular Surgery, Cliniques Universitaires Saint-Luc, Universit  e Catholi- que de Louvain, Brussels, Belgium Key Words: cardiopulmonary bypass; electroencephalogram; hypercapnia; neuromonitoring; suppression NEUROLOGIC COMPLICATIONS still are a major con- cern after cardiac surgery. 1 Moreover, the pathophysiology of neurocognitive function after cardiac surgery remains com- plex. 2 The most currently used noninvasive brain monitors during cardiac surgery are, on one hand, the processed electro- encephalogram (EEG) monitors and, on the other hand, the cerebral oximetry monitors providing regional cerebral oxygen saturation (rScO 2 ) by near-infrared spectroscopy technology. The use of these monitors recently has been recommended, 3 and their combination gives complimentary information that is useful for improving patient care. 4-6 The authors report a case of abrupt EEG suppression owing to an acute hypercapnic event during cardiopulmonary bypass (CPB) and emphasize the importance of neuromonitoring in cardiac surgery. Case Report A 62-year-old-woman experiencing severe coronary artery disease was scheduled for coronary artery bypass graft surgery under normothermic CPB. Her medical background included arterial hypertension and hypercholesterolemia, both well- treated. Physical examination and complementary examina- tions were normal. The patient was monitored according to the institutional guidelines. Neuromonitoring was performed with the depth- of-anesthesia monitor NeuroSENSE NS-701 (NeuroWave Sys- tems, Inc, Cleveland, OH), which was used for bilateral frontal EEG, and rScO 2 (INVOS 5100C; Somanetics Corp, Troy, MI). The hemodynamic and neuromonitoring parameters before the induction of anesthesia are presented in Fig 1. No interhemi- spheric asymmetry was observed on either monitor. The rScO 2 was 55% and 54% for, respectively, the left and right hemi- spheres just after electrode placement. After initiation of full nonpulsatile CPB, systemic hypotension (decrease of >20% of the mean arterial pressure compared with baseline) and cerebral oxygen desaturation (defined as a decrease of >25% compared with baseline) occurred without any frontal EEG modifications. The absence of any EEG changes was rather reassuring. Nevertheless, vasopressors (2 £ 50 mg of phenyleph- rine followed by a continuous infusion of norepinephrine at 0.06 mg/kg/min) were used to increase the systemic perfusion pressure and to treat the cerebral desaturation. Despite restored mean arte- rial pressure, the rScO 2 increased only very slightly and remained extremely low (Fig 2, A). The decision was made to decrease the 1 Address reprint requests to Guillaume Lemaire, MD, Department of Anes- thesiology, Cliniques Universitaires Saint-Luc, Universit e Catholique de Lou- vain, Avenue Hippocrate 10, 1200 Brussels, Belgium. E-mail address: guillaume.lemaire@uclouvain.be (G. Lemaire). https://doi.org/10.1053/j.jvca.2019.07.121 1053-0770/Ó 2019 Elsevier Inc. All rights reserved. ARTICLE IN PRESS Journal of Cardiothoracic and Vascular Anesthesia 000 (2019) 15 Contents lists available at ScienceDirect Journal of Cardiothoracic and Vascular Anesthesia journal homepage: www.jcvaonline.com