Ultrasound-guided supraclavicular vs. retroclavicular block of the brachial plexus: comparison of ipsilateral diaphragmatic function: A randomised clinical trial

Abstract

Background: The 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.

Objective: To compare the effects of supraclavicular and retroclavicular brachial plexus block on diaphragmatic function.

Setting: A single tertiary hospital, study period from December 2017 to May 2019.

Design: Double-blinded, randomised study.

Patients: A 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.

Interventions: Patients were randomised to supraclavicular or retroclavicular brachial plexus block with ropivacaine 0.5%.

Outcome measures: Phrenic 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.

Results: The 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.

Conclusion: The current study confirms the hypothesis that a RCB is significantly less likely to affect ipsilateral diaphragmatic function than a SCB.

Trial registration: Clinicaltrials.gov identifier: NCT02631122.

Fig. 1.. Consolidated Standards of Reporting Trials diagram showing patient recruitment and flow

*Four patients excluded prior to randomisation. One excluded due to pre-operative identification of large pleural effusion. Three patients were excluded due to surgery being postponed (one for elevated potassium, one for neurologic deficits and one for cardiac work-up). CONSORT, Consolidated Standards of Reporting Trials

Fig. 2.. Impact of supraclavicular and retroclavicular block on diaphragmatic function

(a) Diaphragmatic excursion measured using M-mode ultrasound was reduced to a greater degree after supraclavicular than after retroclavicular block (repeated measures analysis of variance P < 0.001). (b) Maximal inspired volume as measured by incentive spirometry was reduced to a greater degree after supraclavicular than after retroclavicular block (repeated measures analysis of variance P < 0.001). PACU, postanaesthesia care unit.

Fig. 3.. Incidence of phrenic block after supraclavicular and retroclavicular block

Phrenic block was defined as more than 50% decrease in diaphragmatic excursion from individual baseline. A greater incidence of phrenic block was observed amongst subjects receiving supraclavicular than retroclavicular block (χ², P = 0.001). DE, diaphragmatic excursion; PACU, postanaesthesia care unit.

Fig. 4.. Extent, timing and distribution of supraclavicular and retroclavicular blocks

(a) No difference was observed in the onset and extent of sensory and motor block of nerves in the distal arm between groups (repeated measures analysis of variance F = 1.559, P = 0.22). Distal arm block score maximal score 27 (three points for each of nine components). (b) Onset and extent of suprascapular nerve block was greater in the supraclavicular group (repeated measures analysis of variance F = 5.065, P = 0.031). (c) Onset and extent of axillary nerve block was greater in the supraclavicular group (repeated measures analysis of variance, F = 4.342, P = 0.045).