Flow Measurement in the Hemodialysis Vascular Conduit for Surveillance of Internal Arteriovenous Fistula: A Trend Analysis

ABSTRACT

PURPOSE: We have already reported on a new method to calculate the intra-vascular conduit flow rate based on Bernoulli's theory for maintaining surveillance of the arteriovenous fistula (AVF) function. To assess the clinical validity of our methods, we examined a trend analysis on the calculated flow rate in hemodialysis vascular conduits. METHODS: From a total of 27 cases of native AVFs that were at least 3 months after construction, we measured the AVF flow rate (Q(D)) with Doppler ultrasonography first. When Q(D) was below 600 ml/min, a fistulogram was taken. The intra-vascular conduit static pressure (ps) was measured, and the flow rate (Q(a)) was calculated every month with using the mean arterial pressure. The patients with a decreased Q(a) of more than 10% over 3 months were referred for a diagnostic fistulogram. RESULTS: Twenty-seven AVFs were studied after 29.5+/-28.5 (4~120) months of operation. The mean Q(D) was 980.6+/-501.6 (144~2,230) ml/min. In 6 patients who showed a Q(D) less than 600 ml/min, 4 pathologic lesions were found on the diagnostic fistulogram juxta-anastomosis stenosis (n=3) and a draining venous stenosis (n=1). Three patients who showed a Q(a) decrement were confirmed as having a draining venous stenosis. However, any unpredictable thrombosis with proximal stenosis (n=2) couldn't be detected. CONCLUSION: Q(a) represents the narrowing of the draining vein of an internal AVF. However, arterial or venous narrowing that is proximal to the arterial puncture site couldn't be detected with the calculated intra-conduit flow rate. The development of new methods that can detect proximal vascular stenosis and that can be used in combination with our method is anticipated in the near future.