Look into the death of George Washington. His doctor responded to what could have been a mild cold by taking a liter of blood 4 separate times from him. Washington very well could have recovered if he was just left alone.

Oh, and the doctor somewhat realized his mistake and tried to put some of the blood back after(!) Washington expired, with the logic that if blood loss killed him giving it back should revive him.

So yeah. Pumping blood back into a dead man. That was done on the founding president of the United States.