Cognitive Effects of Body Temperature During Hypothermic Circulatory Arrest

Purpose of the Study: Determine the effect of deep vs low vs moderate hypothermia on neurocognitive function, brain functional connectivity, and leukocyte SUMOylation patterns after surgical circulatory arrest. Hypothesis: Deep hypothermia is superior to moderate hypothermia in reducing postoperative cognitive decline and preserving brain functional connectivity and that low hypothermia is non-inferior to deep hypothermia. Design and Procedures: 273 informed and consenting patients who are scheduled for elective proximal aortic reconstructive surgery (ascending aorta + aortic valve or root) with concomitant proximal hemi- or total arch replacement via median sternotomy will be randomized to deep (\<20°C), low (20.1°C-24°C), or moderate (24.1°C-28°C) hypothermia during circulatory arrest. Cognitive testing using a standard battery will occur preoperatively (baseline), at 4 weeks, and at 1 year after surgery. Neuroimaging procedures before surgery, and at 4 weeks and 1 year after surgery will consist of high-resolution anatomic, resting-state fMRI (rs-fMRI) and magnetic resonance spectroscopy (MRS) sequences. To characterize leukocyte activation, whole blood will be drawn at 5 time points: at baseline (prior to surgery), before circulatory arrest, 10 minutes after reperfusion, 10 minutes after CPB, and 4 hours after CPB.