Intensive care unit is a section of a hospital in which highly skilled health-care workers provide constant attention and extensive treatment for critically ill patients. There are several specialized types of intensive care units, often called ICU's. The main types are medical ICU's, which care for adults with critical illnesses; surgical ICU's, whose patients have had or are being prepared for major operations; pediatric ICU's, for babies and children; and coronary care units (CCU's), for adults with heart problems.