This is the more common Bier Block, they really are not bad, and my surgeon showed me what he was doing since I was conscious the whole time.
Bier block anesthesia is an intravenous regional anesthesia technique in which an extremity (generally an arm) is made numb for surgery by injecting a local anesthetic solution into a vein after the blood has been squeezed out of the extremity and a tourniquet has been placed on it. The tourniquet prevents the local anesthetic from leaving the extremity and blood from entering it, giving the patient a numb (anesthetic) extremity and the surgeon a bloodless field to work in. The technique is named for August Bier.
The advantages of the technique is that it is simple to perform, and provides a bloodless field that is easy to work in and minimizes blood loss. The disadvantages are that there is a practical time limit on its use (1 - 2 hours) due to the tourniquet restricting blood flow to the extremity. Thus, the tissues of the extremity are not getting oxygen. The extremity could eventually be damaged, and large doses of local anesthetic are required intravenously to produce the numbness. If the tourniquet is released before a large amount of the local anesthetic is metabolized or chemically bound, there is a possibility of a toxic blood level with the attendant problems.
The one they used on me used no anesthetic but had a needle inserted if it got to where I couldn't handle the pain. I never had any pain. My mom cut her finger off on the table saw in their woodworking business right after my second wrist surgery and she requested a Bier Block to have her surgery with. They re-attached it and it's doing well. Her damage wasn't as bad as yours though. I only suggest the Block for those who have drug and anesthesia issues like I do and have a high pain tolerance just in case. But the recovery is so much faster that alone makes it worth it.