Ipsilateral Phrenic Nerve Paresis Associated With Ultrasound-Guided Supraclavicular Block: A Prospective Cohort Study

Ultrasound-guided supraclavicular block (UGSCB) can provide upper limb regional anaesthesia and is an emerging technique in the emergency department (ED). A potential adverse event is phrenic nerve block causing hemi-diaphragmatic paresis, but its incidence in ED remains unclear.

This nested prospective cohort study evaluated adult patients (≥ 18 years) without lung disease who underwent UGSCB for closed reduction of distal radius fractures. UGSCB was performed on the injured side using a two-injection method with 20 mL of 0.75% ropivacaine. The primary outcome was ipsilateral diaphragmatic excursion assessed using bedside ultrasound dynamic imaging before and 30 min post-UGSCB during three respiratory manoeuvres: tidal volume breathing (TV), deep inspiration (DI) and sniff inspiration (SI). Diaphragmatic paralysis was defined as ≥ 75% reduction in diaphragmatic excursion, averaged across the three manoeuvres. Secondary outcomes included vital signs including respiratory rate, oxygen saturations, blood pressure and heart rate.

Sixteen participants were evaluated. UGSCB was associated with reduced ipsilateral diaphragmatic excursion for TV (mean difference [MD] 1.21 cm, 95% confidence interval [95% CI] 0.69-1.75), DI (MD 3.37, 95% CI 2.15 to 4.59) and SI manoeuvres (MD 1.95, 95% CI 1.23 to 2.68). Diaphragmatic paralysis was observed in 10 participants (62.5%). No significant changes in vital signs were observed following UGSCB.

ED physician-performed UGSCB using a two-injection technique was commonly associated with hemi-diaphragmatic paresis, likely due to concomitant phrenic nerve block. However, this was not associated with respiratory or haemodynamic compromise in adult patients without lung disease.