BLOCK AT A GLANCE
Blocks of the terminal branches of the brachial plexus at the level of the elbow.
Indications: Anesthesia and analgesia for hand and wrist procedures
Goal: Injection of local anesthetic (LA) into the tissue plane containing the radial, median, and/or ulnar nerves
Local anesthetic volume: 4 to 5 mL per nerve
Distal peripheral nerve blocks of the upper extremity are very useful for hand and wrist procedures, either as a standalone technique or as a supplement for partial brachial plexus blocks. Ultrasound (US) imaging of individual nerves in the distal upper limb allows for reproducible custom-tailored nerve block anesthesia for a range of clinical indications. Distal nerve blocks are equally suited for hand surgery, like more proximal approaches to the brachial plexus block, but with less extensive motor blockade. A combination of a short-acting proximal brachial plexus block with distal blocks with long-acting LAs also decreases onset time and consistently prolongs analgesia after painful wrist or hand surgery, without the inconvenience of a long-lasting block of the whole arm.
Complete anesthesia of the forearm requires five specific nerve blocks. Two of these are cutaneous nerves (cutaneous antebrachial and musculocutaneous nerves) that can be accomplished by subcutaneous infiltrations distal to the elbow. Separate blocks of five nerves may be less time-efficient, compared to single-injection blocks of the brachial plexus. However, the time efficiency is similar with training. The use of a tourniquet, either on the arm or forearm, usually requires sedation and/or additional analgesia.
Distal peripheral nerve blocks require small-gauge, long-bevel (15°) needles for patient comfort and precision of placement into the delicate fascial sheaths enveloping the nerves. Therefore, additional precautions should be exercised to decrease the risk of intraneural injections when using smaller-gauge, sharp needles (e.g., 25-gauge) for superficial blocks. At the time of this writing, no major manufacturer produced small-gauge, adequately sharpened, 30°, stimulating needles. Note: Full circumferential spread of the LA to surround the nerves is not necessary for a successful block, although this can increase the onset speed.
After emerging from the spiral groove on the lateral aspect of the humerus, the radial nerve passes through the lateral intermuscular septum to enter the anterior compartment of the arm. It continues its path distally between the brachialis and brachioradialis muscles along with the radial collateral artery (Figure 19-1). When the nerve reaches the elbow joint, it divides into the superficial (cutaneous) and deep branches. The superficial branch descends between the brachioradialis and supinator muscles, lateral to the radial artery. The deep branch (also known as the posterior interosseous nerve) reaches the back of the forearm traveling between the two heads of the supinator muscle. The radial nerve provides innervation to most structures in ...