Weekly monitoring of graft access blood flow predicted impending graft failure with 62% sensitivity.
SAN FRANCISCO—A new device may enable clinicians to detect failing graft access blood flow quickly and inexpensively, thereby decreasing the risk of graft failure.
Investigators working with DVX in New York have been studying a new angle-independent Doppler ultrasonic flow detection device called FloMon (DVX, LLC, Princeton, NJ) that can be used by non-specialists weekly. During Renal Week 2007 here, they presented preliminary data from a randomized controlled trial supported by the National Institutes of Health.
In the United States, polytetrafluoroethylene (PTFE) grafts are used for permanent vascular access in about half of all hemodialysis patients. Failure of these grafts is a leading cause of morbidity and it significantly increases overall costs for managing hemodialysis patients.
With the FloMon instrument, a probe is placed directly on top of the graft and three receivers surround a 14 mm diameter central transmitter. A laptop computer is used for data input and storage. The computer displays and calculates the amount of blood at each velocity and provides the sum as the total flow. Bench tests have shown flow-volume errors of less than 3%.
For this trial, 89 patients were randomized into control and monitored groups. The control patients received standard access monitoring once a month as recommended by Kidney Disease Outcome Quality Initiative guidelines. The monitored group had graft blood flow measured weekly with the FloMon device. The average monitoring, performed prior to dialyzing, required only 96 seconds. The investigators defined impending graft failure as a reduction in flow rate to below 550 mL/min or a decline of more than 25% in a week.
In the first 332 patient-months in the control group, 18 grafts failed. In the first 286 patient-months in the monitored group, 13 grafts failed or showed impending failure. In the monitored group, eight impending failures were detected using the monitoring device, a sensitivity of 62%.
Of the five failures missed, three were because of patient non-compliance, one occurred before a baseline flow could be established, and one occurred when a falling flow was not noted. A total of five “false alarms” were noted in the monitored group, for a false-alarm rate of 0.21 per patient-year. Weekly measurements using the FloMon device in hemodialysis patients with PTFE grafts has the potential to save more than $1,000 per patient-year, the researchers reported.
“We conducted this study at three different dialysis centers,” said lead investigator Fidalene Cepeda. “We take three measurements and we chart those measurements every week. Overall, we were able to detect 16 failures out of 30 grafts that were failing in the monitored group.”
Monitoring by current KDOQI guidelines has been shown to be inadequate to detect graft failures, Cepeda said.
Longer lifespan possible
“This device may turn out to be something that can extend the life of a patient,” Cepeda told Renal & Urology News. “Saving the graft will mean less time on dialysis, fewer adverse events for the patients and at the end of the day possibly a longer lifespan.” The device is expected to cost less than $10,000 and it can perform its monitoring in fewer than five minutes prior to dialysis.
The FloMon instrument uses 5 MHz Doppler ultrasound and, for now, is only available as an investigational device.