Variable flow Doppler for hemodialysis access evaluation: Theory and clinical feasibility

Access thrombosis remains an enormous problem for patients on hemodialysis. Current evidence suggests that decreasing access blood flow rate is an imp ortant predictor of future access thrombosis and failure. This article desc ribes a method for determining access volume flow and detecting access path ology. The Doppler ultrasound signal downstream from the arterial needle as a function of the variable hemodialysis blood pump flow rate, is used to d etermine access blood flow. By using this variable flow (VF) Doppler techni que compared with duplex volume flow estimates measured in 18 accesses (16 patients with 12 polytetrafluorethylene [PTFE] grafts and 6 autogenous fist ulas), the results showed a correlation of 0.83 (p < 0.0001) between these methods. In grafts with lower blood flow rates, aberrant flow patterns were observed, including stagnant or reversed flow during diastole while forwar d flow was maintained during systole. When reversed diastolic flow was seve re, it was accompanied by access recirculation. In conclusion, we report th e theory and clinical feasibility of determining access blood flow by using a VF Doppler technique. Measurements are made without the need to determin e the access cross sectional area required for duplex volume flow calculati ons and without the need to reverse the lines required for various indicato r dilution techniques. Important information is also obtained about aberran t flow patterns in patients at risk of access failure.