Bleeding after major surgery, traumatic injury or associated with medical conditions can be life threatening. One of the important supportive treatments is transfusion of blood products, including platelets, and recent evidence suggests that prompt use of the latter is important. Platelets can only be kept for a maximum of seven days after donation, which causes problems with stock control for New Zealand Blood Service (NZBS) and also difficulties with access to platelets at hospitals away from the main cities. NZBS has developed a unique method of preparing and storing platelets at -80oC that allows them to be kept for 1 year and importantly they are able to be defrosted and used at even small hospitals. This study will confirm that the use of frozen platelets is feasible, safe and effective in patients undergoing major cardiac surgery.