In this intervention we will induce only 1 component of the changes at intervention (1), being the increase in MAP of approximately 20 mmHg by administrating 50-100 μg phenylephrine. The CPB enables us to maintain a constant CO and thus eliminating the baroreceptor-reflex. During this intervention NIRS and TCD MCA will be recorded.

With this intervention we will only create a change in CO, which enables us to eliminate the effect of blood pressure. We will modify CPB flow to achieve the CO decrease (in %) measured at intervention (1) meaning: pre-CPB after the bolus of 50-100 μg phenylephrine. In the case of unexpected increase (in %) of CO measured at intervention (1), we will still decrease CPB flow so we will be able to analyse decrease as well as increase in CPB flow. During this intervention NIRS and TCD MCA will be recorded.

In this intervention we will simulate the 'normal' physiological state when administering phenylephrine. We will modify CPB flow to achieve the percentage change CO as observed during intervention (1) as well as administrate 50-100 μg phenylephrine. We expect to see similar outcomes as in intervention (1). During this intervention NIRS and TCD MCA will be recorded.

In this last intervention we will create an increase in MAP without using phenylephrine but only by increasing CO. This enables us to eliminate a possible direct α1-adrenergic effect on the cerebral vasculature. MAP will be raised approximately 20 mmHg by increasing CPB flow 20%. During this intervention NIRS and TCD MCA will be recorded.