Major factors influencing the incidence of surgical wound infection other than site and complexity of surgery, underlying illness, timely administration of prophylactic antibiotics, intraoperative patient temperature, hypovolemia and tissue oxygen tension. The primary determinant of tissue oxygen availability is local perfusion. Thermoregulatory status is one of the major factors influencing tissue perfusion. Local warming induces pre- capillary vasodilation and improves tissue oxygenation. Local warming of surgical wounds may provide a simple and inexpensive way to reduce perioperative wound complications. Specifically, we will test the hypothesis that Warm- Up therapy increases postoperative tissue oxygen tension in patients undergoing cardiopulmonary bypass.