Expected Flow Parameters Within Hemodialysis Access and Selection for Remedial Intervention of Nonmaturing Conduits

Abstract

Background Persistent poor patency rates of arteriovenous fistulae and bridge grafts for dialysis access prompted us to investigate whether flow parameters derived from an initial postconstruction, precannulation duplex study could predict access longevity or direct remedial procedures to salvage nonmaturing conduits.

Methods We analyzed 125 consecutive dialysis access conduits (34 forearm fistulae, 53 arm fistulae, 38 prosthetic bridge grafts, 108 patients, 82 male/26 female, average age 58 years) over the past 5 years having early (2 to 8 weeks) duplex scanning done prior to attempted hemodialysis cannulation. Velocity waveforms were recorded in the arterial inflow, arterial and venous anastomoses, mid-conduit, and in the venous outflow with averaging of volume flow rate (product of average velocity and cross-sectional area) measured at 3 mid-conduit sites. Conduits were deemed “adequate” for dialysis cannulation or “nonmaturing” by the presence of detected high-grade stenoses (peak systolic velocity >400cm/s, velocity ratio >3, and minimal diameter <2 to 3 mm) and subjected to remedial interventions (endovascular or open). Subsequent access function for hemodialysis use and late patency were recorded and correlated with early duplex findings.

Results Average flow rates (forearm fistula 784 ± 623 mL/min, arm fistula 1400 ± 850, bridge graft 1270 ± 604) and mid-conduit peak-systolic velocities (215 ± 214 cm/s forearm fistula vs 312 ± 194 arm fistula) differed between conduit type and location. Remedial interventions were needed in 10 (26%) bridge grafts and 18 (21%) fistulae “nonmaturing” due to occlusive lesions. Conduit flow rates differentiated “nonmaturing” (606 ± 769 mL/min) and “maturing” (1140 ± 857) fistulae (P = .01). A threshold conduit flow rate of 800 mL/min better discriminated failing and functional fistulae and bridge grafts (accuracy 77%) than a flow rate greater or less than 500 mL/min (accuracy 67%). Remedial interventions doubled average flow rates of “nonmaturing” accesses (from 605 to 1159 mL/min) to values similar to “mature, functional” conduits (1374 mL/min) and facilitated a mean duration of patency (12.9 months) equivalent to conduits not needing remedial interventions (11.5 months).

Conclusions Duplex-derived hemodynamic parameters characterized early dialysis access conduit function, prognosticated access patency, guided necessary remedial interventions, and facilitated favorable access longevity.