The Role of Physician-Directed Duplex after Brachial Plexus Block in Arteriovenous Fistula Creation

Background: Best practice guidelines for dialysis access creation emphasize distal sites and autogenous tissue before more proximal sites and synthetic shunts. Pre-operative vein mapping is a useful modality to evaluate optimal access location; however, vein size is often underestimated secondary to patient hypovolemia, room temperature, and basal vascular tone. Supraclavicular brachial plexus blocks (BPB) are routinely performed to provide surgical anesthesia but also have known vasodilatory effects. Although many surgeons use both techniques, most do not repeat vein mapping after BPB to re-evaluate targets after block-mediated vasodilation. Therefore, we evaluated whether the role of physician-directed vein mapping after BPB resulted in more favorable access creations.

Methods: All patients who underwent primary ipsilateral access creation with physician-directed post-block duplex between 2017 and 2018 were evaluated. Vein mapping was reviewed for "theoretical access location" using the criterion of >2.5 mm vessels. Fistula preference was analogous to current indications with the following order of preference: wrist radiocephalic, forearm radiocephalic, brachiocephalic, brachiobasilic, and finally prosthetic graft.

Results: Forty-three patients met inclusion criteria. In total, physician-directed duplex after regional block resulted in the creation of higher preference accesses than predicted in 62.8% of patients. In 34.9% the access was at the predicted level and only 2.3% were at a lower preference. Furthermore, there were no differences in the maturation rates between accesses placed at higher preference locations than predicted compared to those at expected sites (74% vs. 79%, P = 0.38). The overall revision rate for higher preference access was 22.2% compared to 23.1% for equal/lower preference accesses. Of those accesses that failed, 83.3% of new accesses were created at the original theoretical location while 17.7% required placement of a lower preference access.

Conclusions: Physician-directed ultrasound after BPB allows for identification of more preferential targets for access creation compared to pre-operative vein mapping. For access created at more preferential locations than pre-operatively predicted prior to BPB, there was no difference in maturation rates compared to those created at the theoretical vein mapping location.