We will use a retrospective data analysis to evaluate the association of the two vitamin D metabolites 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D with clinical outcome in cardiac surgical patients. The occurrence of several postoperative adverse events such as myocardial infarction, low cardiac output syndrome, stroke and in-hospital death will be assessed from cardiac surgery to discharge. In addition, we will assess the association of the two vitamin D metaboolites with the duration of mechanical ventilatory support and intensive care unit stay from cardiac surgery to discharge. Moreover, in-hospital stay will be assessed according to vitamin D metabolite levels.