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Abstract
Background and Aims Interscalene brachial plexus block confers a high risk of transient phrenic nerve palsy, which may lead to respiratory compromise. Novel ultrasonographic approaches use a high-frequency linear probe to evaluate diaphragmatic functionary simple to perform and easy to teach, therefore accessible to the everyday anaesthetist. We evaluated two techniques in assessing diaphragmatic function after interscalene brachial plexus block.
Methods Two ultrasound techniques: 1) Change in thickness and calculation of the thickening fraction in M-mode as described by Santana et al in 2020 2) Qualitatively and quantitatively determining diaphragmatic excursion in the simplified technique described by El-Boghdadly et al in 2017. Patient parameters including body mass index and respiratory comorbidity, peak expiratory flow rate and local anaesthetic type and volume were recorded.
Results We collected data on 21 patients (all gave consent). Average BMI 28.6 (range 20-42) and average age 54.6 years (range 25-70). 3 patients required oxygen in recovery, 1 had subjective dyspnoea. Ultrasonographic data on diaphragmatic thickening and excursion can be seen in the attached table of results. Average total scan time scan time was 10 minutes (range 5-20).
Conclusions Our results show a greater decrease in both diaphragmatic thickening fraction and excursion on the side of the interscalene block. Point of care ultrasound is a useful technique in identifying phrenic nerve palsy following ultrasound-guided interscalene brachial plexus block. It is a simple and effective technique that can be easily learned, readily applied, and utilised in the acute setting to provide an immediate picture of diaphragmatic function.
Pleural Excursion Ultrasound Image (courtesy of Peter Daum co-author)
Diaphragm Thickness Ultrasound Image (courtesy of Peter Daum co-author) with thickening fraction calculations
Results table.docx