Peri-operative Hemi-diaphragmatic Variations After Brachial Plexus Block Above the Clavicle: A Prospective Observational Study of the Contralateral Side

Abstract

Objective: Hemi-diaphragm palsy after brachial plexus block above the clavicle (BPBAC) occurs frequently, but few patients develop post-operative pulmonary complications (PPC). We hypothesized that contralateral hemidiaphragm function increases after BPBAC. This contralateral function preserves global diaphragmatic function, avoiding PPC in the case of ipsilateral hemi-diaphragm palsy.

Methods: This prospective observational cohort study included 64 adult patients undergoing shoulder surgery with planned BPBAC (interscalene brachial plexus block and supraclavicular block). The Thickening Fraction (TF) was measured by ultrasound in both hemi-diaphragms, ipsilateral (TF _ipsilateral) and contralateral (TF_{contralateral}) to the BPBAC, before and after the surgery. TF_global is the sum of TF_ipsilateral and TF_{contralateral}. PPC were defined as occurrences of dyspnea, tachypnea, SpO₂ <90% or SpO₂/FiO₂ <315.

Results: TF_{contralateral} increased significantly (an average of 40%) after BPBAC (p = 0.001), and TF_ipsilateral decreased (an average of 72%). After BPBAC, 86% of patients had a decreased TF_ipsilateral and 59% of patients an increased TF_{contralateral} at post-operatively. Only 17% of patients have PPC.

Conclusion: After BPBAC, global diaphragm function decreases because of ipsilateral hemi-diaphragm reduction, but less than expected because of increased contralateral hemi-diaphragm function. As a part of diaphragm function, contralateral hemi-diaphragm function must be checked.

Keywords: Brachial plexus block above the clavicle; Diaphragm paralysis; Phrenic nerve palsy; Point-of-care ultrasound; Post-operative pulmonary complications.