Best Practice:

Flow-based surveillance per K/DOQI Guidelines alerts a patient care team to patients at risk for underdialysis, thrombotic events and cardiac failure.

FLOW-BASED ACCESS SURVEILLANCE

Access flow is the quintessential vital sign for an AV Access.  Insufficient flow causes underdialysis. Still lower flow invites thrombosis and too much flow can lead to heart problems —  all with associated morbidities.

Vascular Access Surveillance is recommended by:

• National Kidney Foundation’s K/DOQI Guidelines
• European Renal Association-European Dialysis and Transplant Association’s (ERA-EDTA) European Best Practice Guidelines on Hemodialysis
• Canadian Society of Nephrology for Clinical Practice Guidelines

Transonic Indicator Dilution technology is the recognized gold standard for vascular access surveillance.

AV Access Flow Surveillance - K/DOQI Guidelines

K/DOQI Guidelines include two access flow warning signs that signal need for further monitoring and possible corrective action: 

1. Low-flow Threshold: < 600mL/min for a graft, 400-500 mL/min for a fistula;
2. Flow Trending: 1000 mL/min that has decreased by >25% over 4 months, the patient should be referred for a fistulogram. 

AV Access Flow Trending

Several technologies can monitor low AV access flow (Guideline 1), but only Fast-Response Blood-line Reversal Indicator Dilution Methods (Transonic and possibly Crit-Line saline injection method) can trend flow (Guideline 2):  Their fast-response capability eliminates possible error stemming from cardio-pulmonary recirculation. K/DOQI flow surveillance guidelines were developed from studies using Transonic indicator dilution technology, the recognized Gold Standard.

Surveillance technologies that cannot trend AV access flows include:

• Pressure Surveillance: Only identifies outflow narrowing that may not be hemodynamically significant. Produces false positives that can send patients for unnecessary interventions.¹  
• Duplex Doppler: Precludes use for flow trending due to operator dependency. Demonstrates volume flow conversion errors, and inherent inaccuracy under turbulent flow conditions.
• Slow-Response Blood-line Reversal Indicator Dilution Methods (thermal dilution, dialysance, ultrafiltration): Results affected by cardiopulmonary recirculation. This and low flow reproducibility diminishes the capability for accurate trending.²

References

1. Spergel LM et al, Static intra-access pressure ratio does not correlate with access blood flow. Kidney Int. 2004; 66(4):1512-6.
2. Eloot S et al, Comparison of different methods to assess fistula flow. Blood Purification. 2010; 30:89-95.

Vascular Access Surveillance Reference Lists:

Methodology and Validations of Access Flow Measurement by Krivistki Method

Predictive Power of Access Flow Measurement

Ultrasound Dilution Technology

Pediatric References

• Goldstein SL, Allsteadt A: Ultrasound dilution evaluation of pediatric hemodialysis - vascular access. Kidney Int 59(6):2357-2360, 2001. HD177A

• Goldstein SL, Allsteadt A, Smith CM, Currier H: Proactive monitoring of pediatric hemodialysis vascular access: effects of ultrasound dilution on thrombosis rates. Kidney Int 62(1):272-275, 2002. HD261A