Supraclavicular approaches to brachial plexus anesthesia

Abstract

The concept of a continuous perineural and perivascular space surrounding the brachial plexus from roots to terminal nerves simplifies conduction anesthesia of the upper extremity. As with peridural techniques, the space may be entered at any level, and following the injection of a local anesthetic, the extent of anesthesia will depend on the volume of anesthetic and the level at which it is injected. The single injection techniques based on this concept have resulted in both an increased incidence of success and a decreased incidence of serious complications as compared to the multiple injection techniques used previously. The space above the clavicle, the interscalene space, is potentially just such a space; and it is only after the injection of a local anesthetic that it expands to become a true, fluid-filled compartment. Furthermore, this space is quite extensive in its vertical and horizontal axes but very narrow in its anteroposterior axis. It was for this reason that the original subclavian perivascular and interscalene techniques both called for the needle to be introduced in one of the long axes of the space, whereas the more recently introduced parascalene techniques all call for the needle to be inserted in the very narrow anteroposterior axis. As a result, the chance of the needle leaving the space during the performance of the block is minimized with the subclavian perivascular and interscalene techniques, whereas with the parascalene techniques the slightest movement of even the properly placed needle may cause it to leave the space, resulting in the injection of local anesthetic outside of the fascial compartment. In short, the subclavian perivascular and interscalene techniques of brachial plexus block can provide simple, safe, and effective anesthesia for all types of surgery on the upper extremity and shoulder.