I fear the stopcock. Its one tiny bit of plastic, not much longer than a fingernail, and yet it's the bit responsible for keeping a patient's body fluids on the INSIDE of the body. If it's on a PEG tube, it keeps stomach fluids and gastric acid where they belong. If it's on an A-Line, well then it's holding back the flow of arterial blood.
We need to be able to zero an arterial line on a regular basis, to keep the pressure readings as accurate as possible. To do this, one needs to flip the stopcock so that it is OPEN to atmospheric air, but CLOSED to the patient. If, however, someone has turned OVER the stopcock system because they prefer it that way, and you dont check EXTREMELY carefully...you open the stopcock to atmospheric air, and the patient's arterial blood comes spraying out all over the place. OOPS!!!
It would also be terribly TERRIBLY obvious to everyone concerned what had just happened. As nursing students we take a lot of mocking from hospital staff...I dont like to give them any help.
And this is why I fear the stopcock.