A tough bag of connective tissue surrounds the heart. After cardiac surgery, fluid often collects in the space between this bag and the heart. If too much fluid collects, its pressure can prevent the heart from pumping enough blood to supply the body, a condition known as cardiac tamponade. To prevent this problem, most doctors prescribe nonsteroidal anti-inflammatory drugs (NSAIDs) because inflammation is thought to be the cause of the fluid accumulation, especially when it is present 7 or more days after surgery. Expert recommendations and clinical guidelines encourage this practice.