PHYSIOLOGICAL-ASPECTS IN POSTOPERATIVE CARDIAC PATIENTS

After a cardiac operation, there is reversible myocardial dysfunction that also involves a metabolic disorder. In patients with cardiac fail ure, care must be taken to reduce the strain on the heart by minimizin g systemic oxygen uptake, which is, in fact, the main determinant of c ardiac output. Inotropic support may improve cardiac output and tissue oxygenation in cardiac failure, but it also increases myocardial stre ss directly by increasing myocardial demands and indirectly by increas ing systemic energy demands. Mixed venous oxygen saturation reflects t he balance between cardiac output and systemic oxygen consumption and indicates whether cardiac output can adequately provide the peripheral tissues with oxygen. This physiologic view toward the treatment of po stoperative cardiac failure helps us avoid overtreatment, that is, sti mulating cardiac output more than necessary for adequate tissue oxygen ation. In this way, the strain on the heart can be reduced and myocard ial recovery, enhanced.