An interscalene block is done into the never to your arm and shoulder and it's done near your colar bone. I had it done before having shoulder surgery and it deadens your arm so after surgery you have no pain but can't feel your arm. They missed the nerve and injected it into my blood stream. It made my heart tachycardic and they had to give me meds to slow my heart.

A bier block is done by draining an extremity of blood flow and injecting something like lidocaine and other meds intervieniously into that area. Its said to calm the nerve. From what I read they do the tournicate to keep the anesthetic from flowing into the rest of your body and to keep the blood flow from the area they are injecting.