• Paige L Georgiadis, Kamen V Vlassakov, Megan E Patton, Philipp B Lirk, David R Janfaza, Jose L Zeballos, Aurora N Quaye, Vijay Patel, and Kristin L Schreiber.
• Eur J Anaesthesiol. 2021 Jan 1; 38 (1): 64-72.

BackgroundThe ultrasound-guided retroclavicular block (RCB) is a recently described alternative approach to brachial plexus blockade at the level of the cords. Although more distal blockade of the brachial plexus is thought to be associated with a lower incidence of phrenic nerve block, the impact of RCB on ipsilateral diaphragmatic function has not been formally investigated.ObjectiveTo compare the effects of supraclavicular and retroclavicular brachial plexus block on diaphragmatic function.SettingA single tertiary hospital, study period from December 2017 to May 2019.DesignDouble-blinded, randomised study.PatientsA total of 40 patients undergoing upper extremity surgery below the axilla. Exclusion criteria included significant pulmonary disease, BMI more than 40 and contra-indication to peripheral nerve block.InterventionsPatients were randomised to supraclavicular or retroclavicular brachial plexus block with ropivacaine 0.5%.Outcome MeasuresPhrenic block was assessed by measuring changes in diaphragmatic excursion using M-mode ultrasound, and maximum inspiratory volume on incentive spirometry from baseline, at 15 and 30 min postblock, and postoperatively. Comparative assessment of block characteristics included timing and distribution of sensory and motor block onset in the upper extremity, and scanning and block performance times.ResultsThe incidence of phrenic block in the supraclavicular group was higher by ultrasound imaging (70 vs. 15%) and also by pulmonary function testing (55 vs. 5%), with both diaphragmatic excursion and maximum inspiratory volume decreasing to a greater extent after supraclavicular block (SCB) compared with RCB at 15, 30 min and postoperative time points (repeated measures analysis of variance, P < 0.001). There was no difference in timing and extent of distal arm block, but suprascapular and axillary nerves were more consistently blocked after SCB than after RCB.ConclusionThe current study confirms the hypothesis that a RCB is significantly less likely to affect ipsilateral diaphragmatic function than a SCB.Trial RegistrationClinicaltrials.gov identifier: NCT02631122.

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