Fistula Flow Volumes: How accurate are they in predicting maturity?
William B Harris, Larry R Sprouse, Christopher J Lesar, Heather Mixon, Joel B Clements, Mark Fugate, Charles S Joels, Michael S Greer, Sachin V Phade, Daniel F Fisher
University of Tennessee, Chattanooga, Chattanooga, TN
Color duplex ultrasonography is one of the primary tools used by clinicians in evaluating arteriovenous fistula (AVF) maturity and suitability for hemodialysis (HD). Classically, flow volume (FV) measurements within the fistula in conjunction with venous diameter and physical exam are the primary determinants of maturation. Many vascular laboratories use flow volumes of 500 ml/min to confirm AVF adequacy. We estimate this to be a low number and in fact a poor predictor in fistulas at all locations along the upper extremity of maturation.
We undertook a retrospective chart review of 722 patients in our institution that underwent placement of a new AVF for HD from 2007-2012. Only patients whose FVs were measured 8 to 12 weeks after placement were included in this study, resulting in the exclusion of 434 patients Thus 288 patients were included in the study with 312 total fistulas. Each was rated “Matured” or “Not-Matured” based on clinical evaluation and successful cannulation with two 15-guage needles for HD. Flow volumes were determined in each fistula at this stage. Specifically, fistulas with flow volumes greater than 500 ml/min were evaluated.
233 fistulas were found to have flow volumes of 500ml/min or more. Of these, only 99 fistulas (43%) were suitable for HD at the time of screening. 18 of these were radiocephalic fistulas (RCF), in which the average FV was 767 ml/min in those mature. 57 RCFs did not mature, and in these, an average FV of 463 ml/min was noted. 62 of those matured were brachiocephalic fistulas (BCF). Average maturation velocities in these were 1353 ml/min. 94 BCFs did not mature with an average FV of 984 ml/min. 19 brachiobasilic fistulas (BBF) matured, of which average FV was 1319 ml/min. 53 BBFs did not mature in the allotted time, and FVs in these averaged 953 ml/min.
Utilizing FV to predict the maturity of an AVF for use in HD is generally not accurate at the traditional cutoff of 500 ml/min. This baseline only predicts maturity a fraction of the time, and in fact, significantly higher FVs may be better predictors of adequate access. These baseline values vary based on location of the conduits utilized in creation of the AVF in the upper extremity.
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