Retrograde Versus Antegrade Perfusion in Low-Moderate Hypothermia for Aortic Arch Surgery

Inclusion Criteria:

1. \> 18 years of age
2. Participant's that are scheduled for elective proximal aortic reconstructive surgery (ascending aorta + aortic valve or root) with concomitant proximal hemi-arch replacement via median sternotomy

Exclusion Criteria:

1. \< 18 years of age
2. history of symptomatic cerebrovascular disease, e.g., prior stroke with residual deficit
3. current alcoholism (\> 2 drinks/day)
4. current psychiatric illness requiring pharmacotherapy
5. current drug abuse (any illicit drug use in the past 3 months)
6. hepatic insufficiency (liver function tests \> 1.5 times the upper limit of normal)
7. severe pulmonary insufficiency (requiring home oxygen therapy)
8. renal failure (serum creatinine \> 2.0 mg/dL)
9. claustrophobic fear
10. unable to read and thus unable to complete the cognitive testing
11. pregnant women
12. patients who score \<19 om the Montreal Cognitive Assessment (MoCA) or ≥27 on the baseline Center for Epidemiological Studies Depression (CES-D) scale
13. patients who have pre-existing unsafe implants for 3 Tesla magnetic resonance imaging (MRI)
14. Patients who have received chemotherapy in the last 12 months or radiation to the brain