P1311importance of fistula position for detecting stenosis with vascular access blood flow measurement

Abstract Background and Aims Surveillance of vascular access function in patients on chronic hemodialysis (HD) by measuring the access blood flow rate (Qa) is a widely accepted method for early detection of dysfunction. Qa threshold can be lower in the more distal accesses than in the more proximal accesses. However, cut-off values of Qa in different access positions have not yet been established. The aim of our study is to determine the critical values of Qa indicative of stenosis in different access sites. Method Between July 2012 and July 2019, we performed 5798 Qa measurements of native arteriovenous fistulas (AVFs) (wrist [w]: 2932, forearm [fa]: 2035 and elbow/upper arm [e/ua]: 731) in 242 chronic HD patients using Fresenius 5008 and 5008 S blood temperature monitors (BTMs) at the beginning of HD sessions. As reference we performed 512 colour duplex ultrasonographies (CDUSs) and 205 angiographies (ANGs). CDUS was performed as surveillance method independently from the BTM, or at the presence of low Qa and/or clinical signs of access failure. ANG was performed only in CDUS positive cases or at clinical signs of access failure. We performed percutaneous transluminal angioplasty (PTA) in 174 cases and stent implantation in 2 cases. New AVFs were created in 25 cases. The results were evaluated retrospectively according to access positions using Receiver Operating Characteristic (ROC) curve analysis. Results The number of true positive (TP), true negative (TN), false positive (FP), false negative (FN) cases, sensitivity (SENS) and specificity (SPEC) in different AVF sites and Qas are summarised in table below. Conclusion In order to prevent the fistula occlusion, the cut-off Qas can be different in various access positions. Based on our results we suggest 600-650 mL/min for w AVFs, 650-700 mL/min for fa AVFs and 750-800 mL/min for e/ua AVFs as cut-off values.