Choice of arterial cannulation site during cardiac surgery is controversial. Some physicians in our institution prefer radial artery site, others prefer aortic site (via femoral artery or brachial artery). The investigators aim to compare these two strategies for vasopressor requirement. The study hypothesis is that radial artery cannulation is associated with a larger dose of vasopressor due aortic to radial arterial pressure gradient phenomenon.

Inclusion Criteria:

• Adult patient
• Scheduled for cardiac surgery with cardiopulmonary bypass

Exclusion Criteria:

• More than one arterial cannula at the beginning of the surgery

Adult patients scheduled for cadiac surgery wih cardiopulmonary bypass