John C. Lantis II, MD

 To what extent does proactive vascular access monitoring affect the incidence of AV access thrombosis and abandonment compared with clinical monitoring

 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

 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

 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)

 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)

 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

 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

 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

 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

 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

 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

 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

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

 PSV at the graft venous anastomosis  PSV > 2.0 to immediate upstream velocities is predictive  Positive predictive value of 80%

 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

 RR of access thrombosis  Surveillance 90/406  No surveillance 92/387  RR of access abandonment  Surveillance 94/614  No surveillance 88/347

 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

 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