Intravenous regional anesthesia involves the intravenous injection of local anesthetic distal to an occlusive tourniquet. It is often referred to as a Bier block since the first documented use was by August Bier in 1908. Although it is most commonly employed for surgery on the upper extremity, it has been done on the lower extremity as well. The mechanism of action is felt to be via diffusion of the local anesthetic extravascularly to block distal peripheral branches of nerves. This is in contrast to the more proximal blockade involved in the other common upper extremity regional procedures. A number of adjuncts to local anesthetics have been studied in the block including ketorolac, dexamethasone, opioids, clonidine, and dexmedetomidine. The relative efficacy of these additives, as well as their respective mechanisms of action, is still an open area of study.
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