Peripheral Nerve Blockade

FIGURE 35-1. Schematic of the cervical plexus, which arises from the anterior primary rami of C2–C4. The motor branches (including the phrenic nerve) curl anteriorly around the anterior scalene muscle and travel caudad and medially to supply the deep muscles of the neck. The sensory branches exit at the lateral border of the sternocleidomastoid muscle to supply the skin of the neck and shoulder.

B. Upper Extremity (Figs. 35-5 to 35-7). The four anatomic locations where local anesthetics are placed are the (1) interscalene groove near the cervical transverse processes, (2) subclavian sheath at the first rib, (3) near the coracoid process in the infraclavicular fossa, and (4) surrounding the axillary artery in the axilla. US imaging and NS have greatly facilitated the use of upper extremity regional anesthesia. The terminal branches can also be anesthetized by local anesthetic injection along their peripheral course as they cross joint spaces, where they lie in close proximity to easily identifiable structures or by the injection of a dilute local anesthetic solution intravenously below a pneumatic tourniquet on the upper arm (“intravenous regional” or Bier block) (see Table 38-2).

FIGURE 35-2. Needle insertion points and angles for the deep cervical plexus blockade. The nerve roots exit the vertebral column via the troughs formed by the transverse processes. The needle is inserted at each nerve roots of C2–C4 in a caudad and posterior direction.

FIGURE 35-3. The cervical, thoracic, lumbar, and sacral dermatomes of the body.

FIGURE 35-4. Greater and lesser occipital nerve distribution, supply, and block needle insertion sites.

FIGURE 35-5. Schematic of the brachial plexus. Many branches, including the medial cutaneous nerves of the forearm and arm, which arise from the medial cord, are not shown here.

FIGURE 35-6. Courses of the terminal nerves of the upper extremity. The posterior view (A) illustrates the branches from the posterior cord (axillary and radial nerves), and the anterior view (B) illustrates the branches from the lateral (musculocutaneous and median nerves) and medial (median and ulnar nerves) cords.

FIGURE 35-7. Cutaneous innervation of the upper extremity nerves.

C. Brachial Plexus Blockade (Table 35-3)

D. Terminal Upper Extremity Nerve Blocks. PNBs in the upper extremity are of particular value as rescue blocks to supplement incomplete surgical anesthesia and to provide long-lasting selective analgesia in the postoperative period. The peripheral nerves may be individually blocked at midhumeral, elbow, or wrist locations, depending on the specific nerve. If using US guidance, the elbow and forearm regions appear to be the most suitable block regions, and blocks at these sites may improve the accuracy of nerve localization and local anesthetic spread. The wrist is highly populated with tendons and fascial tissues (flexor and extensor retinaculae), which can be difficult to distinguish from, and may obscure the images of, the nerves. Color Doppler combined with US imaging can be used to clearly identify the nerves at many desirable locations because they are often situated near blood vessels (see Table 35-1 and Figs. 35-7 and 35-8).

E. Intravenous Regional Anesthesia (Bier Block). Arm anesthesia can be provided by the injection of local anesthetic into the venous system below an occluding tourniquet without using US imaging or NS (Table 35-4).

TABLE 35-3 TECHNIQUES FOR BRACHIAL PLEXUS BLOCKADE

Interscalene Block

This block frequently spares the lowest branches of the plexus, the C8 and T1 fibers (which innervate the caudad [ulnar] border of the forearm).

Pneumothorax should be considered if cough or chest pain is produced while exploring for the nerve (cupola of the lung near block site).

Direct injection into the vertebral artery can rapidly produce central nervous system toxicity and convulsions.

Supraclavicular Block

The midpoint of the clavicle is identified. The subclavian artery pulse serves as a reliable landmark in thinner individuals because the plexus lies immediately cephaloposterior to the subclavian artery.

Ultrasound imaging and nerve stimulation help avoid puncturing the pleura. There is a risk of pneumothorax because the cupola of the lung lies just medial to the first rib; risk of pneumothorax is greater on the right side because the cupola of the lung is higher on that side; the risk is also greater in tall, thin patients.

Infraclavicular Block

This block provides excellent analgesia of the entire arm (blocks the musculocutaneous and axillary nerves more consistently) and allows introduction of continuous catheters to provide prolonged postoperative pain relief.

There is a lower risk of blocking the phrenic nerve or stellate ganglion.

Vessel puncture is a potential complication.

Lateral needle insertion helps avoid the risk of pneumothorax.

Axillary Block

This block is useful for surgery of the elbow, forearm, and hand (the musculocutaneous nerve may be blocked separately).

This block is associated with minimal complications (neuropathy from needle puncture or intraneural injection of local anesthetic).

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