Hemidiaphragmatic paralysis following ultrasound-guided anterior vs. posterior suprascapular nerve block: a double-blind, randomised control trial.

Interscalene brachial plexus block provides analgesia for shoulder surgery but is associated with hemidiaphragmatic paralysis. Before considering a combined suprascapular and axillary nerve block as an alternative to interscalene brachial plexus block, evaluation of the incidence of diaphragmatic dysfunction according to the approach to the suprascapular nerve is necessary. We randomly allocated 84 patients undergoing arthroscopic shoulder surgery to an anterior or a posterior approach to the suprascapular nerve block combined with an axillary nerve block using 10 ml ropivacaine 0.375% for each nerve. The primary outcome was the incidence of hemidiaphragmatic paralysis diagnosed by ultrasound. Secondary outcomes included: characterisation of the hemidiaphragmatic paralysis over time; numeric rating scale pain scores; oral morphine equivalent consumption; and patient satisfaction. The incidence of hemidiaphragmatic paralysis was 40% (n = 17) vs. 2% (n = 1) in the anterior and posterior groups, respectively (p < 0.001). In one third of patients with hemidiaphragmatic paralysis, it persisted beyond the eighth hour. The median (interquartile range [range]) oral morphine equivalent consumption was significantly higher in the posterior approach when compared with the anterior approach, whether in the recovery area (20 [5-31 (0-60)] mg vs. 7.5 [0-14 (0-52)] mg, respectively; p = 0.004) or during the first 24 h (82 [61-127 (12-360) mg] vs. 58 [30-86 (0-160)] mg, respectively; p = 0.01). Patient satisfaction was comparable between groups (p = 0.6). Compared with the anterior approach, diaphragmatic function is best preserved with the posterior needle approach to the suprascapular nerve block.