Assessing changes in tissue oxygenation by near-infrared spectroscopy following brachial plexus block for arteriovenous fistula surgery: A prospective observational pilot study

BACKGROUND Near-infrared spectroscopy (NIRS) can be used to measure tissue oxygen saturation (StO2) in different sites and in a wide range of clinical scenarios. Peripheral regional anaesthesia induces vascular changes causing increased arterial blood flow and venodilatation, but its effect on StO2 is still under debate. This is especially so for patients undergoing arteriovenous fistula surgery, wherein latest data suggest an improved outcome under brachial plexus block (BPB) compared with local anaesthesia, but no data are available. OBJECTIVE The aim of this study was to investigate changes in StO2 following BPB prior to arteriovenous fistula surgery using NIRS. DESIGN A prospective observational study. SETTING A secondary teaching hospital from August 2016 to March 2017. PATIENTS Fifteen patients undergoing arteriovenous fistula surgery. INTERVENTION Ultrasound-guided BPB in 15 patients undergoing arteriovenous fistula surgery. OUTCOME MEASURES StO2 at baseline and compared with baseline and the contralateral arm following BPB measured using NIRS of the thenar eminence (NIRSth). RESULTS Baseline values of StO2 assessed by NIRSth were 42.6 ± 7.7% in the arteriovenous fistula arm and 42.7 ± 9.7% in the contralateral arm. There was no significant difference between the two. Five minutes after BPB, there was a significant increase in StO2 of the blocked arm, compared with the control arm expressed as difference of absolute values (7.1 ± 9.7%). At 60 min, an absolute difference of 21.0 ± 13.5% was reached. The absolute increase in StO2 of the blocked arm compared with baseline reached significance after 5 min (8.8 ± 4.6%) and increased up to 23.2 ± 8.2% after 60 min. CONCLUSION NIRSth indicates that BPB significantly increases StO2 of the arteriovenous fistula arm in patients undergoing haemodialysis. TRIAL REGISTRATION: Clinicaltrials.gov: NCT03044496

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