This has appeared in a few past questions; specifically, Question 5 from the second paper of 2016 and the identical Question 15 from the first paper of 2011 ask you to describe "how you would perform blind pericardiocentesis."
Only 25% of candidates passed that question. This is consistent with the expected level of experience of this procedure. Judging by a brief Google search, much of the modern literature on this topic is concerned with harping on about how great it is that this dangerous procedure is dying out, being replaced by safer ultrasound-guided methods.
The approach is as follows:
The college answer also suggests one connect an ECG lead (one of the chest leads) to the base of the needle and watch the ECG to look for a change in the QRS morphology, or ST elevation if the needle contacts the myocardium.
Complications of pericardiocentesis include:
Cikes, I. "A new millennium without blind pericardiocentesis?." European Journal of Echocardiography 1.1 (2000): 5-7.
Fitch, Michael T., et al. "Emergency pericardiocentesis." New England Journal of Medicine 366.12 (2012).
Sternbach, George. "Claude Beck: cardiac compression triads." The Journal of emergency medicine 6.5 (1988): 417-419.
Spodick, David H. "Acute cardiac tamponade." New England Journal of Medicine 349.7 (2003): 684-690.
Reddy, P. SUDHAKAR, et al. "Cardiac tamponade: hemodynamic observations in man." Circulation 58.2 (1978): 265-272.