Reduction in arteriovenous graft impairment: results of a vascular access surveillance protocol.

ABSTRACT

Impairment of hemodialysis (HD) vascular access, remains a frustrating problem for both the patient who possesses an arteriovenous graft (AVG) and the nephrologist who cares for the patient. We instituted a vascular access surveillance protocol intended to detect and correct evolving stenosis in patients with AVGs. The principal screen was the observation of dynamic venous pressure (VP) at a blood flow rate of 200 mL/min during the first 5 minutes of each HD session. If VP at a blood flow rate of 200 mL/min was 140 mm Hg or greater in three of six consecutive readings, recirculation greater than 15% on two observations, graft-arm swelling observed, or prolonged bleeding postdialysis observed, then the patient was referred for angiography and then angioplasty or surgery if a vascular stenosis of greater than 50% was documented. Sixty-four patients with a synthetic AVG comprised the study group. Seventy-two episodes of AVG impairment (56 with stenosis > or = 50% on angiography, 16 with thrombosis) occurred in these patients during the study period. In 63 of 72 impairment episodes, the preceding vascular access screening test was positive. The calculated sensitivity and specificity of the vascular access protocol was 88% and 81%, respectively. Calculation of the sensitivity and specificity for the VP alone was 81% and 85%, respectively. Comparison of the study group with a similar historical control group (55 patients) showed a significantly lower thrombosis rate (P = 0.03; 95% confidence interval [CI], 0.025 to 0.375) in the study group (0.29 thrombotic episodes/graft-year at risk) versus the historical control group (0.49 thrombotic episodes/graft-year at risk). In summary, a vascular access surveillance protocol is a useful tool to predict patients at risk for AVG venous stenosis and/or thrombosis. A dynamic VP of 140 mm Hg or greater appears to be the optimal threshold pressure. A decrease in synthetic AVG thrombosis rate resulted from the use of this surveillance protocol.