What Causes Death Of A Person Undergoing Orthopedic Surgery?

i dont want to ask any question ..i want you to say that on 22nd feb i had my dad operation in mukhopadhaya orthopaedic clinic and research centre and dr.john was operating my dad and he was incharge of him ,my dad couldnt walk without walky so my brother took him for operation.as the opertion was successful ,dr. said that he need blood bt dont want happen my dad xpired .so could you say me,,was this accident took place...........