Suspect cardiac tamponade if there is a sudden cessation of chest drainage during immediate post-operative period. The blood is getting collected in the pericardial space or mediastinurn, compressing the heart that decreases the diastolic filling and therefore cardiac output. It can also be due to clot blocking the chest tube preventing drainage. Treatment is opening of sternal suture line and manual removal of clotted material. The patient may be wheeled back to O.T.