The Effect on Cerebral Oxygenation of Retrograde Autologous Priming of the Cardiopulmonary Bypass Circuit in Cardiac Surgery Patients

The effect of retrograde autologous priming (RAP) on regional cerebral oxygenation (rSO2) still remains unclear, because studies are limited in sample size and study design, and because of the absence of prospective studies. The investigators hypothesize that RAP limits the degree of hemodilution and thereby limits prolonged intraoperative cerebral desaturation during cardiopulmonary bypass (CPB), compared to the conventional priming method. The primary objective of this study is to determine whether RAP limits the degree of hemodilution and limits prolonged intraoperative cerebral desaturation during cardiopulmonary bypass, compared to the conventional priming method. Prolonged intraoperative cerebral desaturation will be assessed by rSO2 desaturation score50. rSO2 desaturation score50 \> 3000 is associated with increased risk of cognitive decline. The investigators hypothesize that RAP limits the degree of hemodilution and thereby limits the incidence of rSO2 desaturation score50 \> 3000 with a relative difference of 50%. The subjects who are divided in the RAP group, the retrograde autologous priming technique will be used, where the patient's own circulating blood partially will be replaced by the priming solution in the cardiopulmonary bypass. In the Control group the conventional priming method will be used. The main study parameters is rSO2 desaturation score50.