Hem-onc patients dies unexpectedly

hi
I had a horrible night a week ago...one of my patients died unexpectedly and i can't seem to forget the event. She was my pt. for 2 previous shifts. I knew she had low baseline BP, and SOB and was being treated for that. She was also transfused with platelets (plt=4) during day shift. When I came in she was doing fine, at midnight she was little SOB but it was not out of the ordinary, she recieved IV lasix for that 2 hrs prior to that. At 2 in the morning the nurses aide came up to me and told me that she was dead. I was very shocked. She was DNR, palliative pt and 93yr old but the death was very unexpected. I find myself guilty for not calling the doc for SOB and low BP at the time. She could have had more lasix to help with SOB. But looking at the situation, this was similar to her previous night. I was surprized that the family coped much better than I thought. I still think something could have been done in this situation.
Did anyone do thru similar situation, and what did u do to cope.