Native arteriovenous fistula blood flow and resistance during hemodialysis

Measurement of vascular access flow (Qa) has been proposed as the ideal method for surveillance of native fistulae. However, debate exists about the influence of blood pressure (mean arterial pressure [MAP]) on Qa during dialysis.

During three consecutive dialysis treatments, 10 patients had paired measurements of Qa and MAP performed at 30, 60, 120, 180, 210, and 240 minutes. Access resistance (AR; in peripheral resistance units, PRUs) was calculated from MAP and Qa values.

Overall pooled coefficients of variation (CVs) for MAP, Qa, and AR were 8.4%, 12.3%, and 12.9%, respectively. A significant reduction in Qa and MAP occurred throughout the dialysis treatment (Qa, 104 mL/min; P = 0.008; MAP, 10.4 mm Hg; P = 0.007). Mean percentages of change in Qa for the first third compared with the middle and last thirds of the session were -4.6% +/- 11.15% (SD) and -9.6% +/- 10.5%, respectively. Thus, Qa varied between 11.4% and -30.6% from baseline during the last hour of dialysis treatments. A stronger correlation between MAP and Qa was seen in radiocephalic (r2 = 0.55; P < 0.0001) compared with brachiocephalic fistulae (r2 = 0.06; P = 0.023). Mean AR was unchanged during the dialysis session (0.23 PRU; P = 0.358). AR for radiocephalic fistulae was significantly greater compared with brachiocephalic fistulae (6.03 +/- 3.90 versus 3.00 +/- 1.11 PRU; P < 0.0001).

Qa could decrease up to 30% from baseline, potentially impairing the ability of Qa to predict impending vascular access failure. AR remained stable during the treatment and may be a more useful measure of vascular access performance as part of an access surveillance program.