DETECTING VASCULAR ACCESS DYSFUNCTION

Access flow (Q(ACC)) is a major determinant of patency. Access recircu lation (AR > 2%), normalized venous intra-access pressure (vP(IA)/MAP) , and Q(ACC) are used to detect access dysfunction. We compared these three measures of access function (ultrasound dilution to measure AR a nd Q(ACC)). A total of 779 measurements were performed on 58 arteriove nous fistulas (AVFs) and 114 polytetrafluoroethylene (PTFE) grafts (1- 8/access) over 13 months, and the access parameters at the beginning o f each period were related to access events within that period. Pump b lood flow averaged >420 ml/min. AR occurred uncommonly (3.8%), and in half the cases, resulted from technical error by staff. In accesses th at thrombosed or underwent intervention for stenosis, AR was present i n only 3 of 11 AVFs and 8 of 57 PTFE accesses. When AR was present in grafts, Q(ACC) averaged 270 +/- 23, and access thrombosis followed unl ess intervention occurred. In grafts, vP(IA)/MAP averaged 0.34 +/- 0.0 1 in those remaining patent, 0.52 +/- 0.08 in those that had undergone intervention, and 0.54 +/- 0.04 in those that had thrombosed. Q(ACC) averaged 1,121 +/- 26, 605 +/- 45, and 550 +/- 65 ml/min, respectively , in the three groups. By contrast, Q(ACC) differed significantly in p atent AVFs (1,053 +/- 35) compared with failing AVFs (363 +/- 48), but vP(IA)/MAP did not. AR is thus a late manifestation of access failure . Q(ACC) is the best diagnostic test of access dysfunction in AVFs. In terpretation of vP(IA)/MAP in grafts is enhanced by periodic Q(ACC) me asurements.