Old, dried blood can be a challenge to get out, especially if the quilt has been put in the dryer. But here are some things worth a try (separately, not mixed together):
White vinegar (soak for 30 min, then rinse)
Toothpaste (rub gently onto fabric, let dry, then rinse)
Hydrogen peroxide (dab onto blood, soak for 30 min, then rinse)
Meat tenderizer (be careful... wet fabric, sprinkle on, let dry, then rinse)
I hope it works, but my motto is, 'a quilt isn't a quilt without a drop of blood on it'.