Efficacy and Safety of Phrenic-Nerve Sparing Blocks vs. Interscalene Brachial Plexus Block for Shoulder Surgery.

PURPOSE OF REVIEW: Shoulder arthroplasty is often associated with significant postoperative pain, making effective analgesia a crucial part of surgery day. The interscalene brachial plexus nerve block (ISB) is the gold standard for regional anesthesia in otherwise healthy patients. However, its use is limited by a high incidence of ipsilateral phrenic nerve paralysis, which may result in respiratory compromise, particularly in patients with chronic obstructive pulmonary disease (COPD), reduced pulmonary reserve, or preexisting diaphragmatic dysfunction. The incidence of hemidiaphragmatic paralysis (HDP) is often cited as high as 100% given the location of the phrenic nerve in relation to the brachial plexus roots, which are blocked with an ISB. This review aims to consolidate current evidence on phrenic-sparing nerve block techniques for postoperative analgesia following shoulder arthroplasty. RECENT FINDINGS: Growing interest has emerged in alternative regional anesthesia techniques that minimize phrenic nerve involvement while maintaining adequate analgesia. Several phrenic-sparing approaches have been described in recent literature, with varying degrees of efficacy and safety. These techniques aim to reduce the incidence of hemidiaphragmatic paralysis while still providing clinically meaningful pain control in the postoperative period. These phrenic sparing nerve blocks include the superior trunk block, the suprascapular block, the infraclavicular block, the axillary block, and the erector spinae block when performed either solo or in combination. Phrenic-sparing nerve blocks represent a promising alternative to ISB, particularly for patients at increased risk of respiratory complications. While current evidence supports their potential to provide effective analgesia with reduced diaphragmatic impairment, further high-quality studies are needed to establish optimal techniques and standardize their use in clinical practice.