First, don't be overwelmed. There is a lot to do during heart surgery, but you will learn it. Not in the first couple of days, but over your heart rotation you will get a routine and feel much more comfortable than when you begin
If the CRNA you are working with will let you, watch as much of the surgery as possible. It really took a lot of pressure off me the first time to not worry about charting and really focus on the surgery and the anesthesia and how they match up. I was really lucky, and this is what I did the first open heart I had: helped set the room up - this takes some getting used to b/c there are lots of drips, etc. that need to be ready, put the a-line in, watched the mda put the swan in, intubated, hooked up monitors, then monitored the patient until chest incision. Then, the CRNA let me watch what the surgeon did and helped me learn the timing of things like lungs down, heparin, titrating drips to get pressure where you want it for cannulation, and all the other things you will learn (be prepared to have BP problems when coming off CPB and after protamine). This was a great way to learn, and I hope that you will have the same opportunity. I also hope that any CRNAs who precept students in the heart room reading this will take it into consideration for us SRNAs doing our first heart.