Feeling guilty about not doing more

For some background, I'm a new grad nurse (graduated in April) who did my preceptorship on this ICU unit and have been working on my own since July.

Yesterday I received a patient from the OR who just had heart surgery. Her blood pressure was dropping and her chest tubes were very clotted with increased outputs. I let the charge nurse at the time know of these new findings and the drips she was currently on. At the time, I felt very uneasy like I felt like something bad was going to happen but I waved it off as some of our patients who come back from surgery have labile blood pressures and chest tubes can become clotted. Also, the charge nurse did not seem too concerned at the time and had told me to monitor for the next hour. As the night goes by, her blood pressure had continued to drop and she needed more vasoactive medications. Again, I let the charge nurse know and by that time the chest tube losses were minimal and there were no clots despite after stripping the chest tubes. In my head, I was thinking she might just need some more fluid for her blood pressure. I was told to get recent lab values and her CVO2 was low. So the charge nurse had called the physician on call and the patient was started on other inotropic medications along with some fluid boluses. After I get all that sorted and see that the patient is relatively stable, I go on my break and give report to my buddy. When I had come back, she was having a cardiac tamponade and she would go back to the OR to have the fluid drained.

I wish I would've stuck with my gut feeling that something was not right in the first place. Now that I look back at it, some obvious signs were there: low blood pressures, clotted chest tubes. But at the same time I had never experienced a patient with cardiac tamponade and other signs like an increased CVP, and tachycardia weren't present and I had thought the chest tube issue was resolved so I didn't think of tamponade. I just feel extremely bad and feel like I could've advocated for my patient and they would have detected the tamponade earlier. The signs were there and I can't help but feel guilty and think that I could have done more in this situation. I have been thinking about this for the past day now and it definitely makes me more motivated to be better and do better but at the same time I don't feel very competent enough to be working in the ICU.