Vascular Access Monitoring: A Key to Optimum Hemodialysis Care

Abstract

Most people with renal failure are hemodialysis dependent for their renal replacement therapy. Arteriovenous (AV) fistula in the forearm or arm is considered the best vascular access for a hemodialysis patient. Fistulas are associated with less morbidity and mortality and are recommended over grafts or catheters. KDOQI has for the last decade promoted the Fistula First Initiative. The incidence of stenosis and thrombosis is higher in AV grafts than in native AV fistulas. Catheters are a nightmare for any dialysis unit as they are associated with infection, bacteremia, sepsis, clotting, poor flows, venous sheath formation, and central venous stenosis, and yet they are the only option for some patients on dialysis. Vascular access morbidity (stenosis, thrombosis, infection, missed treatments, hospitalizations) costs more than $8,000 per patient year at risk, representing approximately 15% of the total Medicare expenditures for end-stage renal disease annually.1 So, what is the key to improving AV access outcomes? There are various methods of AV access surveillance, but the key is a dedicated vascular access team approach. This access team can be composed of dialysis nurses, a vascular access coordinator, nephrologists, interventionalists, and the surgeon. Physical examination of the vascular access should be a part of routine nephrologist and nursing rounds. Asif et al. found that physical exam can accurately detect fistula stenosis.2 Inspect catheters; look for signs of infection, such as drainage and redness. Inspect AV fistulas/AV grafts; look for edema, redness, aneurysms, and collateral veins. Auscultation normally gives a continuous low-pitched bruit. A vigorous one may indicate an abnormal lesion. Strong pulsation of the outflow vein is often mistaken as evidence of a well-functioning fistula rather than a signal of a developing outflow vein stenosis. Pulse augmentation, performed by occluding the access downstream from the arterial anastomosis and evaluating the strength of the pulse, may reveal an inflow problem. Elevation of the extremity should normally result in collapse of the fistula. If the vein remains dilated and full on elevation, this could indicate venous/outflow stenosis or thrombosis.3 Duplex Doppler ultrasound, blood flow monitoring, and endovascular imaging can detect the stenosis or clot that was suspected on physical exam.4 Duplex ultrasound can reveal flow patterns, depth and sizes of vessels, stenotic lesions, and collateral veins.5 Venous blood flow (Qb) pressure monitoring during dialysis sessions, periodic access blood flow (Qa) measurement, and access recirculation (Ar) measurement have all been shown to detect angiographically significant stenosis (<50%).6 A trend of increasing Qb measured at a consistent blood pump speed and Qa >500 mL/min both must be worked up with a fistulogram. These tests are the gold standard tools for detecting developing stenosis and for predicting thrombosis. Simple cues to stenosis or thrombosis in fistulas or grafts also include falling urea clearance (measured as urea reduction ratio or Kt/V), frequent clotting of dialysis tubing, suboptimal blood flow rates, and difficulty in cannulating the fistula.4 Once the referral for interventionist is sent, it may be possible to angioplasty a stenotic lesion, declot a fistula, stent a recurring central stenosis, or place coils in accessory veins, all under fluoroscopic guidance, and by doing so salvage and increase the life span of the fistula or graft.7 If all of the above fails, the surgeon should be consulted, and revision of the AV fistula might be warranted.8 In summary, monitoring of vascular access by physical exam, dialysis outcomes, surveillance tools, and interventions is key to keeping a vascular access working optimally and thereby reducing patient morbidity and mortality and having a more efficiently functioning dialysis unit.9 A dedicated vascular access team approach is vital to a dialysis unit for superior patient care and reducing the number of hospitalizations and missed treatments.10 In conclusion, this approach should be the standard of care for dialysis units.