Surveillance of arteriovenous hemodialysis access: a systematic review

1. John C. Lantis II, MD Surveillance of arteriovenoushemodialysis access: a systematic review

2. Question • To what extent does proactive vascular access monitoring affect the incidence of AV access thrombosis and abandonment compared with clinical monitoring

3. The problem • Hemodynamically significant outflow stenosis leading to thrombosis is the most common cause of prosthetic access abandonment • Early studies suggested idntification and correction of these stenosis could prevent thrombosis and prolong graft longevity • RCTs have had variable results

4. However..despite the evidence? • The National Kidney Foundation • The Canadian Society of Nephrology • Caring for Australians with Renal Impairment • Recommend frequent, regular surveillance with physical exam an some form of serial access flow measurements

5. The literature • Nine studies (1363 patients) • Surveillance vs. clinical monitoring • Surveillance followed by intervention led to a non-significant reduction in risk of thrombosis (.82) • …..and a non-significant reduction in abandonment (.80)

6. The literature • Three studies (207 patients) compared the effect of vascular intervention vs. observation in patients with abnormal surveillance results Intervention led to a significant reduction in the risk of access thrombosis (0.53) …and abandonment (0.76)

7. The studies • 2006 Robbin • Chronic HD – mean follow up 670 days • Prosthetic only • Surveillance • 65 pts • US every 120 days • Thrombosis 18, abandonment 27 • Control • 61 pts • Physical exam/HD parameters TIW • Thrombosis 27, abandonment 26

8. The studies • 2006 Polkinghorne • Chronic HD – mean follow up 558 days • Autogenous only • Surveillance • 68 pts • Blood flow every 30 days • Thrombosis 6 • Control • 67 pts • Physical exam/dynamic venous pressure TIW • Thrombosis 4

9. The studies • 2005 Malik • Chronic HD – mean follow up 670 days • Prosthetic 216, Autogenous 147 • Surveillance • 291 pts • Urea recirculation, dynamic and static venous pressure, ultrasound – weekly • Abandonment 7 • Control • 72 pts • No access monitoring • Abandonment 28

10. Clinical Monitoring • The value of surveillance strongly depends on the adequacy of clinical monitoring • Clinical monitoring by skilled personnel has a positive predictive value of 70 to 90% in prosthetic grafts, a 38% sensitivity and 90% specificity

11. Technical Remarks • Monitoring – is physical exam per DOQI guidelines • Absent thrill, pulsatile graft, abnormal auscultation, persistent edema, venous collaterals on the chest wall • Surveillance – refer to tests • Serial access flow measurements • Serial measurement of static dialysis venous pressure • Prepump arterial pressure • Duplex ultrasound screening

12. Serial access flow measurements • flow rates as measured at end of dialysis • < 600 ml/min • Or a decrease of 25% • Most useful for autogenous fistula • Reverse the arterial and venous lines measuring the rate of change in ultrasound transmission in the venous line after saline • DOQI recommends: Monthly measurement

13. Static venous dialysis pressure (VDP) • Primarily for grafts • (Dynamic VDP) – measured at low HD flow of 200 ml/min is a relative poor marker, too many variables • Static VDP – at no dialysis flow • Ratio to SBP • >0.4 suggestive of stenosis • >mean pressure ratio is 0.5 • Should use as a trending tool, not a single measurement

14. Prepump arterial pressure Indicitive of the ease with which blood is drawn from the access at any particular setting New autogenous access, if they have a problem it is at the arterial inflow Therefore, have an excessively negative arterial dialysis pressure Useful in new dialysis fistulae

15. Duplex Ultrasound Imaging • PSV at the graft venous anastomosis • PSV > 2.0 to immediate upstream velocities is predictive • Positive predictive value of 80%

16. General Comments • Note although thrombosis rates are lower, actual access survival is no different in the two groups • However, lower incidence of thrombosis may translate into a reduction in access related costs and hospitalizations

17. Totals • RR of access thrombosis • Surveillance 90/406 • No surveillance 92/387 • RR of access abandonment • Surveillance 94/614 • No surveillance 88/347

18. Conclusions • Very low quality evidence • Suggests that serial surveillance of asymptomatic AV access, accompanied by intervention if an abnormality is found, tends to decrease thrombosis and abandonment vs. no surveillance • This difference is not statistically significant

19. SVS Clinical Recommendations • Regular clinical monitoring (inspection, palpation, auscultation and monitoring for prolonged bleeding after needle withdrawal) to detect access dysfunction –very low quality evidence • Suggest access flow monitoring or static dialysis venous pressures for routine surveillance – very low quality evidence • Suggest performing a Duplex ultrasound study or contrast imaging in accesses that display clinical signs of dysfunction or abnormal routine surveillance – very low quality evidence