This is a procedure that should be done in cardiac cath lab under fluoroscopy. In emergency situation it can be done bedside also.
When there is a large collection of fluid or blood around the heart which compresses the heart and so blood pressure falls quickly (known as cardiac temponade), it has to be aspirated on emergency basis. This can results in low cardiac output which leads to shock like state.By aspirating fluid, life of the patient can be saved.
The patient undergoing pericardiocentesis is supine position with little elevation of head end. Most common site for aspirating the fluid is subxiphoid process. It should be done under echocardiographic guidance.