Background and aims Interscalene brachial plexus (IS) block is associated with an 80 to 100% rate of hemidiaphragmatic paresis. a combined block of the suprascapular and axillary nerves, also called shoulder block, is an analgesic alternative; however, the respiratory complications associated with this block have never been investigated. This randomised controlled single-blinded trial tested the hypothesis that a shoulder block would result in less respiratory complications, when compared with an IS block, while providing similar analgesia.
Methods Thirty ASA I-II patients scheduled for elective shoulder arthroscopy under general anaesthesia were randomly allocated to an IS block or a shoulder block using a 20 ml-volume of local anaesthetics administered under ultrasound-guidance. the primary outcome was rate of hemidiaphragmatic paresis (diaphragmatic excursion reduction>75%), measured by M-mode ultrasonography, before and 30 min after the procedure. Secondary outcomes were functional respiratory outcomes measured with a bedside spirometry, along with duration of analgesia and pain scores.
Results Demographic data were similar between groups. Rates of hemidiaphragmatic paresis were 80% (95%CI:52–96%) and 13% (95%CI:2–40%) in the IS and shoulder groups, respectively (p<001). Functional respiratory outcomes were significantly better preserved in the shoulder group (table 1). Pain scores were reduced in the IS group at 2 postoperative hours but increased at 24 hours, when compared with the other group, while morphine consumption was equivalent (table 2).
Conclusions A shoulder block reduces rate of hemidiaphragmatic paresis, with less impact on respiratory function. Differences in pain scores during the course of the study may probably be the result of rebound pain.
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