I feel like a terrible nurse. I am a fairly new nurse and usually work in the PICU. I pride myself in being very safe and I am not afraid to ask questions at all. I am orientating to the SICU to help out while all this COVID stuff is going on. I expressed to them my fear with taking CRRT because I have never done it in the PICU. They said that they would never do that. My second day I was given a pt that was on CRRT (I still had a preceptor who told me they probably just did it cause I was with her - I only got two days of orientation). I am always up to learn new things so I was asking questions and taking it all in. I have help out in the PICU before and all they have to do in the SICU is switch out the bags and troubleshoot. So the first bag needed to be replaced. My preceptor mixed the bag - which I did not see and I hung it with her watching me and she said I did it right. The next time she was in the room with me, but I was fairly confident because she had watched me do the first one. However, I did not mix the bag!! I didn't even know I needed to do this! I was never taught. Yes I should have realized, but I didn't. She was also in the room with me. So it ran until the machine started beeping something was wrong and I got her immediately. We couldn't return the blood because there was air in the line and he probably didn't get the right stuff for about 4 hours. They wanted to switch him the HD anyways and his labs actually looked great, but I feel horrible and like a terrible nurse and cannot let it go. Everyone told me it has happened before but I just don't know if it has and I feel like I shouldn't be a nurse or should be fired.