RT Journal Article SR Electronic T1 Depth of cervical plexus block and phrenic nerve blockade: a randomized trial JF Regional Anesthesia & Pain Medicine JO Reg Anesth Pain Med FD BMJ Publishing Group Ltd SP rapm-2021-102851 DO 10.1136/rapm-2021-102851 A1 Mathias Opperer A1 Reinhard Kaufmann A1 Matthias Meissnitzer A1 Florian K Enzmann A1 Christian Dinges A1 Wolfgang Hitzl A1 Jürgen Nawratil A1 Andreas Koköfer YR 2022 UL http://rapm.bmj.com/content/early/2022/01/09/rapm-2021-102851.abstract AB Background and objectives Cervical plexus blocks are commonly used to facilitate carotid endarterectomy (CEA) in the awake patient. These blocks can be divided into superficial, intermediate, and deep blocks by their relation to the fasciae of the neck. We hypothesized that the depth of block would have a significant impact on phrenic nerve blockade and consequently hemi-diaphragmatic motion.Methods We enrolled 45 patients in an observer blinded randomized controlled trial, scheduled for elective, awake CEA. Patients received either deep, intermediate, or superficial cervical plexus blocks, using 20 mL of 0.5% ropivacaine mixed with an MRI contrast agent. Before and after placement of the block, transabdominal ultrasound measurements of diaphragmatic movement were performed. Patients underwent MRI of the neck to evaluate spread of the injectate, as well as lung function measurements. The primary outcome was ipsilateral difference of hemi-diaphragmatic motion during forced inspiration between study groups.Results Postoperatively, forced inspiration movement of the ipsilateral diaphragm (4.34±1.06, 3.86±1.24, 2.04±1.20 (mean in cm±SD for superficial, intermediate and deep, respectively)) was statistically different between block groups (p<0.001). Differences were also seen during normal inspiration. Lung function, oxygen saturation, complication rates, and patient satisfaction did not differ. MRI studies indicated pronounced permeation across the superficial fascia, but nevertheless easily distinguishable spread of injectate within the targeted compartments.Conclusions We studied the characteristics and side effects of cervical plexus blocks by depth of injection. Diaphragmatic dysfunction was most pronounced in the deep cervical plexus block group.Trial registration number EudraCT 2017-001300-30.Data are available upon reasonable request. Study protocols and raw data are available upon reasonable request from the corresponding author.