Babies having heart surgery often have problems after surgery with their blood pressure and getting enough blood to their bodies. To treat this they require medicines to keep their blood pressure high enough to get blood to their bodies. The side effects of these medicines include fast heart rates and increasing the amount of work the heart has to do. Corticosteroids are made by the body and help to use the energy in the food people eat, control the chemicals in their blood and maintain their blood pressure. Corticosteroids made by the body may be decreased in patients that have major surgery. Corticosteroids help to increase blood pressure and can decrease the amount of blood pressure medicines a patient requires. Corticosteroids have been shown to increase blood pressure in patients with bacterial infections and in very small, premature babies but have only been studied in a few babies who have had heart surgery. The way corticosteroids work is unknown but may involve decreasing the body's response to being on a heart-lung machine or give steroids not being made by the patient.