The aim of the investigators' research program is to investigate the effects of perioperative high dose selenium supplementation in high-risk cardiac surgical patients undergoing complicated open heart surgery. The investigators hypothesize that the therapeutic strategy tested in this randomized trial may contribute to a fewer complications, less organ injury and fewer deaths. Before the investigators conducted the large definitive trial, they conducted a pilot study to assess the feasibility of the protocol, and are rolling the pilot patients into the definitive trial.