Upper Extremity Multiple Stimulation Techniques

Andrea Casati

Blocks of the brachial plexus and the terminal nerves using a single-injection technique require a large volume of local anesthetics and their diffusion through several barriers before reaching the nerves. In addition, it has been established that with a single-injection technique the intensity of the block is not uniform among the nerves. Thus, the block of the brachial plexus using a single-injection technique with an interscalene approach often misses the ulnar nerve, and with an axillary approach it often misses the musculocutaneous or the radial nerve.

In a recently published meta-analysis of single-, double-, and multiple-injection techniques for axillary brachial plexus block, Handoll and Koscelniak-Nielsen (2006) reported a statistically significant decrease in primary anesthesia failure (RR 0.24, 95% CI 0.13 to 0.46) and incomplete motor block (RR 0.61, 95% CI 0.39 to 0.96) in the multiple-injection group as compared to those in the single-injection group. Similarly, when comparing multiple with double injections the meta-analysis showed a statistically significant decrease in primary anaesthesia failure (RR 0.23, 95% CI 0.14 to 0.38) and incomplete motor block (RR 0.55, 95% CI 0.36 to 0.85) in the multiple-injection group versus the double-injection group.

The time for block performance was significantly shorter for single and double injections compared with multiple injections, but the requirement for supplementary blocks in these groups tended to increase the time to readiness for surgery. This provides evidence that multiple-injection techniques using nerve stimulation for axillary plexus block provide more effective anesthesia than do either double- or single-injection techniques.

Moreover, with the introduction of imaging techniques for peripheral nerve block placement, the importance of needle reorientation to optimize the diffusion of the local anesthetic solution around different nerves and branches involved in the nerve block has become even clearer.

In this chapter we discuss general principles of multistimulation for the most commonly used approaches to the brachial plexus block. Multistimulation has been reported with axillary, interscalene, midhumeral and infraclavicular approaches to the brachial plexus. However, considering the greater number of needle passes in the proximity of the pleural cavity and large blood vessels that cannot be compressed in case of unwanted vascular puncture, multistimulation with the infraclavicular approach should be reserved for those with significant experience.

Interscalene Multistimulation Technique

To perform an interscalene block using a multistimulation technique, three different muscular responses should be elicited: (a) contraction of the deltoid muscle, induced by stimulation of the superior trunk (C4-5 roots); (b) contraction of the biceps with flexion of the forearm, induced by stimulation of the middle trunk (C6 root); and (c) contraction of the triceps muscle with extension of the forearm, induced by stimulation of the inferior trunk (C7 root).

Patient Position: Supine, with the head slightly turned away from the side where surgery will be performed.

Needle Size: A 22-gauge, 25-mm insulated needle.

Volume: 6 to 8 mL per trunk.

Anatomic Landmarks: The interscalene groove formed by the anterior and middle scalene muscles is palpated at the level of the cricoid cartilage (C6). This can be facilitated by palpating the posterior border of the sternocleidomastoid muscle and rolling the finger laterally and posteriorly to feel the scalene muscle. If the groove is not palpated, the patient can be asked to take a slow and deep breath to facilitate its location. The interscalene groove is marked. Next a horizontal line is drawn at the level of the cricoid cartilage. The site of introduction of the needle is the intersection between these two lines.

Approach and Technique: The insulated needle connected to a nerve stimulator (1.5 mA, 2 Hz, 0.1 ms) is introduced at a 45° angle, in a caudal and posterior direction, and is advanced slowly until it produces a specific motor response. The first motor response usually observed is the contraction of the deltoid muscle (superior trunk). The position of the needle is then adjusted to maintain the same motor response with a current of 0.5 mA. For shoulder surgery this is the most predictive response of a good block, deserving a larger part of the local anesthetic volume. Thus, after negative blood aspiration, 8 mL of local anesthetic solution is injected slowly. Next, the insulated needle is withdrawn to the level of the skin and the intensity of the current is increased to 1.5 mA. The needle is then reintroduced in a slightly more caudal direction (3° to 5°) toward the midpoint of the clavicle and the groove between the pectoralis major and deltoid muscles, in search of stimulation of the middle trunk (contraction of the biceps muscle with flexion of the forearm). After positioning the needle to allow for an appropriate motor response with a current of 0.5 mA, 6 mL of local anesthetic is injected following negative aspiration for blood. The insulated needle is again withdrawn to the level of the skin, and the intensity of the current set back to 1.5 mA. The needle is reintroduced in a slightly more caudal direction (3° to 5°) in search of a stimulation of the inferior trunk (contraction of the triceps muscle with the extension of the forearm). After the appropriate motor response is maintained with a current of 0.5 mA, another 6 mL of local anesthetic is injected slowly following a careful aspiration test.

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