Chapter 18: Blocks for Analgesia of the Shoulder: Phrenic Nerve Sparing Blocks

INTRODUCTION

This chapter describes several strategies to accomplish analgesia to the shoulder joint by blocking distal nerves of the brachial plexus that supply innervation to the shoulder joint. Distal blocks preserve the mobility of the arm and hand, and diaphragmatic function by sparing the phrenic nerve. Therefore, distal blocks can also be used in patients with borderline respiratory function.

GENERAL CONSIDERATIONS

The selective blockade of the peripheral sensory nerves innervating the shoulder emerged as an alternative analgesic technique to the interscalene or supraclavicular brachial plexus blocks to avoid hemidiaphragmatic paresis. The course of the sensory nerves supplying the shoulder joint enables different injection sites, distant from the trajectory of the phrenic nerve and different combinations of blocks:

• Shoulder block: Selective blocks of the suprascapular and the axillary nerves, which innervate most of the shoulder joint (Figure 18-1). Of note, the shoulder block does not provide surgical anesthesia like an interscalene block; instead, it provides analgesia and decreases opioid consumption after shoulder surgery.

• Block of the suprascapular nerve in combination with an infraclavicular brachial plexus block, selective block of the lateral and posterior cords, or a costoclavicular block. This combination anesthetizes most components of the brachial plexus that supply innervation to the shoulder joint (Figure 18-1), and therfore, it results in a more complete analgesia.

Specific Risks and Limitations

There are no specific contraindications other than the general considerations for regional anesthesia techniques. However, shoulder blocks in obese patients may be challenging because adequate ultrasound (US) images of the suprascapular and axillary nerves may be difficult to obtain. Anatomical variations of the suprascapular notch are common and may render US guidance challenging. Consequently, compared to interscalene blocks, shoulder blocks are less time-efficient and cause a greater degree of patient discomfort because they require two punctures. The limitations and risks of infraclavicular blocks are discussed in Chapter 15.

ANATOMY

The shoulder joint innervation is complex and involves multiple branches of the brachial plexus. The suprascapular nerve (C5, C6) is a mixed sensory-motor nerve that originates from the upper trunk of the brachial plexus and travels ...