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Reduction in arteriovenous graft impairment: results of a vascular access surveillance protocol
A V Cayco1, A K Abu-Alfa, R L Mahnensmith
1Section of Nephrology, Yale University, New Haven, CT 06520-8029, USA.
Insights
A new surveillance protocol for hemodialysis (HD) arteriovenous grafts (AVGs) effectively detects stenosis and thrombosis. This protocol, using dynamic venous pressure (VP), reduced graft thrombosis rates in patients undergoing HD.
Area of Science:
- Nephrology
- Vascular Surgery
- Medical Device Monitoring
Background:
- Vascular access impairment is a significant challenge for patients with arteriovenous grafts (AVGs) undergoing hemodialysis (HD).
- Early detection of stenosis and thrombosis is crucial for maintaining AVG functionality and patient outcomes.
Purpose of the Study:
- To evaluate the effectiveness of a novel vascular access surveillance protocol for detecting and managing AVG venous stenosis and thrombosis.
- To assess the sensitivity and specificity of the protocol, particularly dynamic venous pressure (VP), in identifying AVG impairment.
Main Methods:
- Implemented a surveillance protocol monitoring dynamic venous pressure (VP) at 200 mL/min during HD sessions.
- Referred patients for angiography and intervention if VP ≥ 140 mm Hg, recirculation >15%, graft-arm swelling, or prolonged bleeding occurred.
- Compared thrombosis rates in a study group using the protocol with a historical control group.
Main Results:
- The surveillance protocol demonstrated high sensitivity (88%) and specificity (81%) in detecting AVG impairment.
- Dynamic venous pressure (VP) alone showed 81% sensitivity and 85% specificity with a threshold of 140 mm Hg.
- The study group exhibited a significantly lower thrombosis rate (0.29 episodes/graft-year) compared to the historical control group (0.49 episodes/graft-year).
Conclusions:
- The implemented vascular access surveillance protocol is a valuable tool for predicting and managing AVG venous stenosis and thrombosis.
- A dynamic VP threshold of 140 mm Hg appears optimal for early detection.
- The protocol successfully reduced the rate of synthetic AVG thrombosis.
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.