Comparing Hypothermic Temperatures During Hemiarch Surgery

Inclusion Criteria: * Age ≥ 18 years * Elective aortic hemiarch surgery * Planned unilateral selective anterograde cardioplegia * Anticipated lower body arrest time of \< 20 minutes * Able to provide written informed consent Exclusion Criteria: * Surgery for acute aortic dissection or emergent operations * Total arch replacement * Inability to perform unilateral selective anterograde cerebral perfusion (uSACP) * Patients with known/documented coagulopathy * Patients with cold agglutinin disease or those that test positive on routine preop screening * Pre-existing severe neurological impairment or inability to accurately assess neurocognitive function as determined by the operating surgeon * Severe carotid disease, defined as: any patient with previously documented carotid stenosis of \> 70% (via Doppler ultrasound (US), magnetic resonance angiography (MRA), or computer tomography angiography (CTA)) without neurological deficits; or carotid stenosis \> 50% with neurological deficits; or previous carotid endarterectomy or stenting * Patients in renal failure or currently being treated with renal replacement therapy (RRT) or estimated glomerular filtration rate (eGFR) \< 30 ml/min/1.73m2 * Use of an investigational drug or device at time of enrollment * Participation in another clinical trial which interferes with performance of the study procedures or assessment of the outcomes