局所麻酔薬：静注局所麻酔としての臨床応用

Intravenous regional anesthesia or the Bier block technique uses exsanguinated or blood-drained vessels to transport local anesthetics or LAs to the peripheral nerve trunks. This technique is mainly used for surgeries on the upper extremity.

In this technique, an IV cannula is placed close to the surgery site. Then the arm is raised to drain the blood passively. Starting from the cannula insertion site, the arm is tightly bandaged to obstruct blood flow.

Next, a tourniquet is placed around the proximal arm and inflated to 100 mm HG above the patient's systolic blood pressure  to isolate the veins from the systemic circulation. After removing the bandage, the LA is injected into the cannula to pass through the exsanguinated veins.

The injected LA causes complete anesthesia of the extremity within 10 minutes. However, the tourniquet should remain inflated for 30 minutes to prevent the LAs from entering the systemic circulation.

Premature deflation of the tourniquet causes the pain to return quickly and releases toxic levels of LA into circulation.