Sister- age 54 bariatric sleeve,died 7hrs after surgery while in hospital from hemerage.

I was present when sister was brought to her room complaining of severe pain not like she ever experienced previously (2 knees surgery , gout,) pain meds not working. I noticed no urine output ,tubing was clean and bag was clean and slightly folded I advised nurse of my observation . Aid took temp 2x it was 95.5 her skin color very white/pale and sweating, nurse was in and out of room, when questioned I was told this is normal because she was in pain,I made sure she was as comfortable as possible and I went home at 9:45pm then at 3:10am Dr. called to say "something is wrong" raced back and she was pronounced dead at 3:32am.I was advised by ME that the actual Bariatric sleeve was a success and that there was no leakage(ME tested many times)she told me her insides were so badly mangled she could not find where the 2 liters of blood came from .She said she should not have died and she would have had great success and reach her goal. I feel that signs of bleeding were missed.