Fluorescent Imaging Evaluation of Lidocaine Distribution Following Bier Block in the Upper Extremity

Bier block regional anesthesia has been used as an alternative to general anesthesia for years. Despite multiple theories and multiple techniques to delineate the location of the action of lidocaine during Bier block anesthesia, there has not been a consensus on the location of action. The purpose of this study was to use fluorescent imaging to further investigate the site of action of lidocaine during Bier block.

Three patients with carpal tunnel syndrome underwent open carpal tunnel release with Bier block anesthesia performed in the standard fashion with 1cc of Indocyanine green (IcG) mixed with lidocaine. Fluorescent images were obtained at the time of injection and after 10 minutes to allow patients to reach the level of surgical anesthesia. Repeated imaging was obtained at the time of completion of the procedure or at 30 minutes of tourniquet time.

At time 0, IcG was distributed along the superficial venous system of the hand and forearm. At 10 minutes, the distribution of IcG was within the capillary system and infiltrating the dermis. The distribution later saturated the capillary beds and remained present until release of the tourniquet.

The authors demonstrate that some lidocaine action occurs at the cutaneous level during the administration of a Bier block. Due to limited field depth of view provided by the SPY® Elite System (Novadaq Technologies Inc., Mississauga, Canada), we are unable to draw any conclusions as to the distribution of the IcG or lidocaine at the level of the larger nerves at the site of the tourniquet.