Diaphragm‐sparing effect of the infraclavicular subomohyoid block vs low volume interscalene block. A randomized blinded study

Background Both low volume interscalene and infraclavicular‐subomohyoid blocks were suggested to provide shoulder analgesia with low risk of phrenic nerve block. The aim of this study was to compare the frequency of the phrenic nerve block between these two techniques. Method Seventy‐two patients scheduled for shoulder arthroscopy were included in this randomized controlled blind study. Before induction of general anesthesia, patients received low volume interscalene block using 5 mL of ropivacaine 0.5% (LVS group) or infraclavicular‐subomohyoid block using 25 mL of ropivacaine 0.5% (ISO group). The diaphragmatic excursion was measured (using ultrasound) before the block and after surgery. If the ratio of postoperative to pre‐block excursions was