Vasc-Alert is a solution for providing ongoing access site surveillance for hemodialysis patients. Vasc-Alert works by taking the treatment run data routinely collected during dialysis and using it to detect the increase in pressure in the access due to stenosis. Once the pressure in the access exceeds a certain threshold, Vasc-Alert issues a report to the center staff, prompting intervention.

Studies have shown that the early detection of vascular access stenotic lesions, followed by timely corrective procedures, reduces the thrombosis rate and prolongs access survival (1). It is widely held that monitoring for an elevation in venous line pressure, which increases as a stenosis develops, would have clear diagnostic value (2).

Vasc-Alert's approach conveys many benefits. First, no personnel need to administer the test, saving staff time. A test is performed with each treatment, rather than just once a month. And since Vasc-Alert is looking at pressure and not blood flow, it can detect the growth of stenosis earlier so that intervention can take place before the stenosis gets too advanced.

The staff at Henry Ford Health System developed the venous access pressure ratio (VAPR) test to predict access failure using data routinely collected during the dialysis session. The VAPR algorithm uses the treatment run data such as pressure inside the venous drip chamber (VDP), Qb, arterial pressure, and blood pressure to identify patients at-risk for access problems. It also takes into consideration the type of machine and the needle/tubing being used, the height of access relative to the drip chamber and the patient's hematocrit to determine the actual pressure in the access site. The result is then compared it to the patient's mean arterial pressure to develop a ratio. If the ratio is high for three consecutive treatments, it is an indication of stenosis.

Figure 1: Arteriovenous graft showing stenosis and higher venous pressure

1. Besarab, et al. “Utility of intra-access pressure monitoring in detecting and correcting venous outlet stenosis prior to thrombosis” Kidney International. 1995
2. Schwab. “Vascular Access for hemodialysis.” Nephrology Forum. 1999