Although most upper extremity regional anesthesia is accomplished by means of various approaches to the brachial plexus, there are occasions when individual terminal nerves or their branches are blocked selectively. There are generally three instances in which the anesthesiologist desires to perform these selective nerve blocks. First, some surgical sites are partially innervated by sensory nerves that are not part of the brachial plexus or not consistently anesthetized with plexus blocks. This chapter describes how and when to anesthetize the most common of these nerves—the supraclavicular, the suprascapular, and the intercostobrachial. The second indication is when the block of the entire brachial plexus block is not necessary for the planned procedure. In this case, selective upper extremity cutaneous anesthesia or analgesia may involve blocking terminal nerves (radial, median, or ulnar nerves) or their branches (lateral and medial antebrachial cutaneous nerves) distally at the elbow. A final and controversial indication for selective upper extremity nerve blocks is their use as a supplement to an incomplete brachial plexus block.
When considering the application of these various blocks, the reader is reminded that innervation of the upper extremity is often variable and overlapping.1 Therefore, when faced with the choice of performing a single nerve block versus blocking several adjacent nerves, it is advisable to err on the side of multiple blocks, particularly in those adjacent cutaneous areas that represent potential crossover innervation (Figures 80H–1 and 80H–2). The relevant anatomy will be covered with specific nerve block description.
Cutaneous innervation of the upper extremity. Actual patients demonstrate large variation in the depicted pattern of innervation and significant crossover between nerves.
Idealized distribution of the cutaneous innervation of the upper arm and forearm.
Local Anesthetic and Adjuvant Selection
Local anesthetics for individual upper extremity nerve blocks are selected for their desired duration of anesthesia and/or analgesia. If intermediate-acting local anesthetics are selected (lidocaine or mepivacaine), duration can be increased with either adjuvant epinephrine (2.5 mcg/mL). Neither adjuvant significantly increases duration if a long-acting local anesthetic such as bupivacaine or ropivacaine is chosen.1
SUPRACLAVICULAR NERVE BLOCK INDICATIONS
The supraclavicular nerve provides sensory innervation to the “cape” of the shoulder (Figure 80H–3). Commonly anesthetized as a component of cervical plexus block for carotid surgery, the supraclavicular nerve may also require blockade for surgery involving the shoulder or supraclavicular area. Local anesthetic spread in an interscalene plexus block often blocks the cervical plexus and therefore it is adequate to block the supraclavicular nerve, but the nerve is frequently not anesthetized with a supraclavicular brachial plexus block.
Supraclavicular nerves, derived from C3–C4 nerve roots, is not part of the brachial plexus, ...