(Continuing the story from the bottom of the previous page.)
I consulted a friend later, about what I could/should have done. She does pitbull rescue and is a vet tech. She said the only things you can do when a pitbull has hold of someone (human or animal) are:
1) Pick up the dog by its hind legs and swing it in circles until it lets go. If you are strong enough.
2. Beat it over the head with something until you give it a concussion.
This is from someone who loves pitbulls and rehabilitates them every day. They are very nice dogs mostly but they do not like to stop in the middle of an attack.