7 Selective Blocks of Individual Nerves in the Upper Arm, at the Elbow, and Wrist
7.1 Radial Nerve Block (Middle of Upper Arm)
The radial nerve passes under the middle of the humerus in the radial groove to reach the outside of the upper arm and then enters the elbow on the radial side of the flexor aspect (Fig. 7.1, Fig. 7.2, Fig. 7.3).
The arm is positioned as for perivascular axillary plexus anesthesia. In the middle of the upper arm, the gap between the flexors and extensors is found. The posterior border of the humerus is palpated. Coming from below (below the brachial artery), the posterior border of the humerus is found with a 4 to 8 cm long needle (Fig. 7.2). On bone contact, an attempt is made to advance the needle a little further under the humerus. The technique should generally be performed with the nerve stimulator and an immobile needle or using ultrasound, particularly if an axillary block has already been performed. When there is a clear response to a corresponding stimulus and pulse duration, 8 to 10 mL of the local anesthetic is injected with repeated aspiration.
Needle: 4 to 8 cm
Tips and Tricks
The motor response should be in the hand (extension of the wrist or fingers).
Sensory and Motor Effects
Sensory and motor loss in the region of the radial nerve distal to the injection site.
Supplement to brachial plexus anesthesia.
It has proved useful to perform this block in combination with (supplementing) a perivascular block (Fig. 7.4) if the radial nerve was not specifically stimulated when the axillary block was performed. Unlike the “multistimulation technique,” this method is associated with directly finding only one nerve and is presumably preferable from the aspects of time required and patient acceptance, and is comparable with the multistimulation technique with respect to effectiveness. Using ultrasound is helpful (Chapter 7.13).
7.1.3 Radial Nerve Block of the Upper Arm Using Ultrasound
Linear transducer: 10 to 12 MHz
Needle: 6 cm
The arm is abducted as for a perivascular axillary plexus block or as described in Chapter 7.1. The transducer is placed in the short axis in the middle of the upper arm so the radial nerve is visible as a strongly hyperechoic structure in the region of the radial groove at the posterior edge of the humerus (Fig. 7.5). From here, the nerve can be followed proximally for a certain distance, but can no longer be found at half the distance between the anterior segment of the acromion and the lateral epicondyle in 99% of patients (Foxall et al 2007). In the region of the radial groove, the radial nerve is accompanied by the deep brachial artery, whose position with respect to the radial nerve is variable (Foxall et al 2007).
The needle is inserted using the in-plane or out-of-plane technique.
Placement of a catheter is not described.
7.2 Blocks at the Elbow
After passing under the humerus, the radial nerve appears at the elbow on the radial side between the brachioradialis and the brachialis muscles lateral to the biceps tendon (Fig. 7.6). Here it divides into a sensory superficial branch and a thicker, mainly motor deep branch (Fig. 7.7).
The lateral cutaneous nerve of the forearm is the sensory terminal branch of the musculocutaneous nerve and provides the sensory innervation of the radial side of the forearm. It lies on the radial side; since it is already epifascial lateral to the biceps tendon it is very superficial (Fig. 7.7).
The median nerve, which crossed the brachial artery from lateral direction at the upper arm, passes through the elbow medial (on the ulnar side) to the brachial artery (mnemonic: median nerve—medial; Fig. 7.6 and Fig. 7.7).
The ulnar nerve passes through the ulnar groove and lies subfascially dorsal to the medial epicondyle and then disappears between the two heads of the flexor carpi ulnaris muscle (Fig. 7.8 and Fig. 7.9).
7.2.2 Radial Nerve Block (Elbow)
The extended arm is abducted and externally rotated and the forearm is supinated. The biceps tendon can be palpated easily. The puncture site is 1 to 2 cm lateral (radial) to the biceps tendon at the level of the intercondylar line. The (stimulation) needle is advanced slightly proximally and laterally in the direction of the lateral epicondyle of the humerus (Fig. 7.10). After producing a response, 5 mL of local anesthetic is injected.
The block can also be performed using a nerve stimulator or ultrasound guidance.
A catheter can also be inserted here.
7.2.3 Musculocutaneous Nerve Block (Elbow)
The lateral cutaneous nerve of the forearm, a sensory terminal branch of the musculocutaneous nerve, is already very superficial in the elbow region. It is blocked by subcutaneous infiltration lateral to the biceps tendon in the direction of the lateral epicondyle of the humerus with a 24G or 25G needle about 5 cm long (Fig. 7.11 and Fig. 7.12).
The technique can be readily combined with the technique of radial nerve block at the elbow.
The creation of a Cimino shunt in conduction anesthesia is an indication for a combined radial nerve and musculocutaneous nerve block.