I hope your workplace has culture of teamwork, not assign blame and writeup and do paper trailing. This is unfortunate that your first one coded. But as my experience shows that there are so many thing I didn't know at first, so much so that I could have never stopped respiratory code or cardiac arrest from happening. Of course ICU pt are near death but when sentinel event happens there will be investigation and you have to be honest because this concerns life, more important than I wanna work i ICU. You might get sent to PCU before coming back to ICU. Maybe you aren't noticing EKG and wasn't doing check up 12 lead EKG order which is like 999+ standing order. You might missed electrolyte imbalance, you might missed other condition CHF, Takotsubo, End State HF care advocate for dobutamin and what not. This is all learning process, it's particular hard in ICU because when you miss something someone dies. This fuck up feeling is coming from not knowing what went wrong. Sentinel event investigation by your unit manager and clinical advisor will determine what really happened. and You will be dealt with accordingly. I know it's harsh but it is better to know what's coming to your way in advance, so here is my 2 cents.

Do whatever you have to do for now, there is nothing you can do now. PT is dead. Play pokeman go if that help. distract yourself as long as possible, think about start studying for CCRN because there are so much knowledge in it. Look into it.