ASDIN 9th Annual Scientific Meeting

1

Ongoing Controversies in

Dialysis Vascular Access Surveillance

William D. Paulson, MD

Charlie Norwood VA Medical Center

and

Georgia Regents University

Augusta, Georgia, USA

No disclosures

PROGRESSIVE STENOSIS

DECREASED FLOW

ACCESS THROMBOSIS & FAILURE

Flow surveillance paradigm

CASE REPORTS

NONRANDOMIZED STUDIES

SMALL SINGLE CENTER RCTS

LARGE MULTICENTER RCTS

PARADIGM

How paradigms should be established

CASE REPORTS

NONRANDOMIZED STUDIES

SMALL SINGLE CENTER RCTS

LARGE MULTICENTER RCTS

PARADIGM

How flow surveillance paradigm

was established

ASDIN 9th Annual Scientific Meeting

2

Application of WHO criteria

Undesired Condition: Thrombosis

The natural history of access thrombosis (stenosis

leading to thrombosis) should be predictable &

understood

There should be an early latent stage of low flow that

allows time for intervention that reduces thrombosis

Flow does not

accurately predict thrombosis

Paulson, Sem Dial 2001

Flow & decrease in flow had sensitivity of 80% at

false-positive rates of 50–60% in predicting thrombosis

Graft blood flow has poor predictive accuracy

Ram AJKD 2008

Application of WHO criteria

ASDIN 9th Annual Scientific Meeting

3

Screening test: Access flow

Flow must be accurate & reliable in detecting stenosis

that causes thrombosis

There should be well-defined thresholds for intervention

referral that confirm presence of significant stenosis

Flow is not stable

Ram,

Sem Dial 2005

Q =MAP −−−− CVP

R

Why is flow unstable?

MAP, CVP, R all vary during dialysis

MAP in 2 representative patients

DeSoto, AJKD 2001

Does stenosis control flow?

Artery Graft Vein

Luminal diameters control relation

between flow & stenosis

Artery Graft Vein

ASDIN 9th Annual Scientific Meeting

4

Mathematical model helps explain why

accesses thrombose without warning

White, CJASN 2006

A V

Application of WHO criteria

The intervention:

Angioplasty with or without stenting

Preemptive intervention should provide more benefit

than harm.

High false positive rate probably yields many

unnecessary angioplasty procedures that may promote

neointimal hyperplasia

Application of WHO criteria

The desired outcome

There should be evidence from RCTs that surveillance is

effective in reducing thrombosis & prolonging access

survival

ASDIN 9th Annual Scientific Meeting

5

Flow surveillance

does not increase access survival

Tonelli AJKD 2008

Observational studies

of graft thrombosis were biased

Allon,

NephSAP 2007

Poor-quality reports are associated with bias that leads to

overestimating benefits of interventions

Strippoli, JASN 2004

Surveillance fails all 4 WHO criteria

Conclusion:

Access surveillance is a false paradigm

Dialysis units must have an ongoing program

of vascular access surveillance

ASDIN 9th Annual Scientific Meeting

6

Access surveillance statement by 17

nephrologists, interventionists, researchers

Surveillance as a New York jobs program

• Once a paradigm is established, challenges to its

validity are usually resisted even as new evidence

accumulates indicating paradigm is not valid.

• Data that contradict or refute established paradigms

are often rejected or ignored

• It is paramount to apply rigorous criteria when

developing guidelines

The nature of paradigms

“Wisest is he who knows he knows not” - Socrates