Noninvasive blood flow measurement in expanded polytetrafluoroethylene grafts for hemodialysis access

Volume flow rates were measured in 31 expanded polytetrafluoroethylene grafts (6 mm) of 26 patients undergoing hemodialysis. Flow was calculated from the known access graft diameter and by measurement of the mean Doppler shift frequency waveform. Overall flow rates were 750 +/- 383 ml/min (range, 0 to 1921 ml/min). There was no difference in flow between grafts anastomosed to either antecubital or upper arm veins but there was a significant difference in flow rate between straight and loop grafts (652 and 914 ml/min) and between grafts anastomosed to the radial, distal brachial, and proximal brachial arteries (648, 876, and 1169 ml/min, respectively). Flow rates measured during a preocclusive 14-day period in five grafts were significantly lower than flow rates in grafts that remained patent for at least 2 weeks following examination (307 +/- 172 vs. 849 +/- 346 ml/min). This is a safe, repeatable noninvasive measure of access graft hemodynamics, which may be useful as a functional monitor and a warning of impending failure.