Diaphragm-Sparing Nerve Blocks for Shoulder Surgery

Abstract

Shoulder surgery can result in significant postoperative pain. Interscalene brachial plexus blocks (ISBs) constitute the current criterion standard for analgesia but may be contraindicated in patients with pulmonary pathology due to the inherent risk of phrenic nerve block and symptomatic hemidiaphragmatic paralysis. Although ultrasound-guided ISB with small volumes (5 mL), dilute local anesthetic (LA) concentrations, and LA injection 4 mm lateral to the brachial plexus have been shown to reduce the risk of phrenic nerve block, no single intervention can decrease its incidence below 20%. Ultrasound-guided supraclavicular blocks with LA injection posterolateral to the brachial plexus may anesthetize the shoulder without incidental diaphragmatic dysfunction, but further confirmatory trials are required. Ultrasound-guided C7 root blocks also seem to offer an attractive, diaphragm-sparing alternative to ISB. However, additional large-scale studies are needed to confirm their efficacy and to quantify the risk of periforaminal vascular breach. Combined axillary-suprascapular nerve blocks may provide adequate postoperative analgesia for minor shoulder surgery but do not compare favorably to ISB for major surgical procedures. One intriguing solution lies in the combined use of infraclavicular brachial plexus blocks and suprascapular nerve blocks. Theoretically, the infraclavicular approach targets the posterior and lateral cords, thus anesthetizing the axillary nerve (which supplies the anterior and posterior shoulder joint), as well as the subscapular and lateral pectoral nerves (both of which supply the anterior shoulder joint), whereas the suprascapular nerve block anesthetizes the posterior shoulder. Future randomized trials are required to validate the efficacy of combined infraclavicular-suprascapular blocks for shoulder surgery.

Randomized comparison between interscalene and costoclavicular blocks for arthroscopic shoulder surgery

“…HDP after ISB stems from two possible mechanisms: rostral LA spread toward the C3–C5 nerve roots or LA migration from the interscalene groove towards the phrenic nerve 1. At the C6 level (where ISBs are commonly performed), the phrenic nerve is situated on the anterior scalene muscle a mere 0.18 cm from the brachial plexus 1. However, as the phrenic nerve and the brachial plexus move caudally, they start to diverge from each other at a rate of 3 mm/cm 21.…”

“…However, because the shoulder joint and its adjacent structures derive their sensory innervation from the lateral cord (ie, lateral pectoral nerve), posterior cord (ie, axillary and subscapular nerves), and upper trunk (ie, suprascapular nerve),1 too distal an approach may fail to anesthetize one of these neural structures (especially the suprascapular nerve). Thus, during the inception phase of our trial, we hypothesized that the CCB would constitute the ‘sweet spot’, as it could reliably anesthetize the lateral and posterior cords11 and, through the purported retrograde channel to the supraclavicular brachial plexus,12 the suprascapular nerve as well.…”

“…Postoperative analgesia after shoulder surgery remains a challenge in patients with pre-existing pulmonary pathology, as interscalene brachial plexus block (ISB), the standard nerve block for shoulder surgery, carries a prohibitive risk of hemidiaphragmatic paralysis (HDP) 1. Although several diaphragm-sparing nerve blocks have been proposed, to date, none seems to offer equivalent analgesia to ISB while avoiding HDP.…”

Ultrasound-guided subomohyoid suprascapular nerve block and phrenic nerve involvement: a cadaveric dye study

“…ISB, the accepted gold standard regional anesthetic technique for perioperative shoulder analgesia,2 was associated with a high incidence of phrenic nerve blockade in the past3 and continues to do so, despite abundant alterations in techniques 4…”

Retroclavicular approach to infraclavicular brachial plexus block: a logical conundrum

“…More holistic solutions exist and include the (more shallow) supraclavicular or axillary approaches 2. Admittedly, these approaches may entail a higher incidence of phrenic nerve block7 or an increased number of needle passes 8. If the operator favors an infraclavicular brachial plexus block (eg, for the easy securing of perineural catheters), the arm could be abducted to decrease the depth of the brachial plexus 9.…”