To investigate the role of postoperative nausea and vomiting risk factors assessment after cardiac surgery. We designed a randomized controlled study comparing standard care (no risk factor assessment and no intervention) with prophylaxis of postoperative nausea and vomiting after cardiac surgery in high risk patients. Prophylaxis of postoperative nausea and vomiting by betamethasone (4mg) and/or droperidol (0.625mg) immediately after cardiac surgery, depending on risk factors (if risk score is over 2) in the intervention arm.