A Bier block is a procedure used to treat chronic pain of the lower arm or leg. A tourniquet is placed on the arm or leg and medicine is injected into that limb. The medicine is left in place for 30 minutes before the tourniquet is let down. Your hand or foot will be numb during this procedure. This procedure is used to treat sympathetically mediated pain and can be useful in people who have Chronic Regional Pain Syndrome (CRPS or RSD).