How dangerous is a pericardial window. also how dangerous is getting put under. thanks?

Tamponade: Pericardial window is performed to drain fluid accumulated around the heart ( blood, serous, pericarditis) as it builds up constricts the heart, and prevents normal filing of the cavities. On inspiration, the pulse amplitude decreases, the heart is pumping empty and on expiration the pulse amplitude improves. The drainage, depending of the severity can be done with a large bore needle, OR,live an underwater drain and the patient stay in the ICU, until the drainage reduces in volume and the hemodynamics are normal. This procedure is frequently performed in the ER, post cardiac surgery, post viral infections or post MI.