Hemodialysis: Check flow rates with imaging to predict access function
The construction of radiocephalic arteriovenous fistulas (RC-AVF) only achieves successful hemodialysis (HD) in around 40 percent of end-stage renal disease (ESRD) patients.
Could the RC-AVF flow measured by ultrasound 30 days after the construction be used to predict successful HD? Researchers at the David Geffen School of Medicine in Los Angeles investigated the issue and found a flow rate of 400mL/min as the key threshold (Pillado E et al, Flow Rates at Thirty Days after Construction of Radiocephalic Arteriovenous Fistula Predict Hemodialysis Function, Ann Vasc Surg. 2018 doi: 10.1016/j.avsg.2018.01.068).
41 patients were included in the study. The authors used color Doppler ultrasound to measure cephalic vein outflow volume at 3 forearm sites, 1 and 3 months postoperatively. Within the first 30 days after surgery, 61 percent of patients with a forearm RC-AVF proceeded to successful AVF dialysis, 10 percent had HD via central venous catheter, and around a third (29%) ceased function.
The flow results: Mean flow at 30 days for patent fistulas was 629 ml/min, which had increased to 663 mL/min by the third month. 8 patients (27.6%) had a flow rate of <400 mL/min; 2 of these clotted, 2 of 3 with closed revisions went on to HD, and 1 patient died. By contrast, of the 21 patients with a flow rate ≥400 mL/min, 19 (90%) functioned for HD, and 2 (10%) AVF occluded before 1 year. This meant that 81 percent of patients with a flow rate ≥ 400mL/min had achieved successful 1-year patency, vs. 62 percent of the low-flow fistulas.
An RC-AVF flow rate of ≥400 mL/min in the first month predicted more successful HD than low flow (<400 mL/min) (81% vs. 62%). The authors warn that without intervention, “low flow rates do not improve significantly and maturation is unlikely”. They therefore strongly recommend imaging for all patients at 30 days to identify and correct stenosis in a timely manner in patients with low flow rates.