If you are infusing blood slowly you do not need the level one. The level one is only used when blood products need to be administered quickly. You are correct about changing tubing after 4 units if administering blood traditionally. However the tubing on the level one is good for 4 hrs and I have used it for about that long with a trauma victim one day. But the other response is correct, if someone is bleeding that bad they need to go to OR ASAP.