Hypotension and AV access thrombosis: Causation or just association?

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Aisha Shaikh

Aisha Shaikh (Memorial Sloan Kettering Cancer Centre, New York, USA) has staked out a claim that, though hypotension was “associated” with arteriovenous access (AV) thrombosis, it should be far from the only consideration in choosing an access modality. She did so while presenting at VEITHsymposium (15–19 November, New York, USA).

Shaikh began by drawing attention to the fact that chronic hypotension in ESKD patients is often caused by poor cardiac function, autonomic dysfunction or a combination of both. Chronic hypotension is associated with increased risk of AV access thrombosis, and AV access thrombosis in turn is associated with poor outcomes, Shaikh said. She stated that high AV access flow can lead to heart failure especially in the setting of poor myocardial reserve, which can in turn can lead to hypotension. Therefore, she argued, in patients with chronic hypotension it is peritoneal dialysis (PD) that is the preferred dialysis modality as it causes less blood pressure variability.

With this in mind, she reminded the audience of the three vascular access options for the chronically hypotensive ESKD patients who are not candidates for PD: an arteriovenous fistula (AVF), an arteriovenous graft (AVG) or a central venous catheter (CVC). Functional AV fistulae carry lower risk of thrombosis and infection compared to AV grafts and CVCs.

Next, Shaikh discussed the findings of a study led by Tara I Chang (Stanford University, Palo Alto, USA) that investigated the association between intradialytic hypertension and the risk of AV access thrombosis. In this study, intra-dialytic hypotension increased the risk of AVF thrombosis. Low pre-dialysis and post-dialysis systolic blood pressure were associated with increased risk of AVF and AVG thrombosis. Furthermore, patients in the higher quartiles of intradialytic hypotension were older, tended to use AVG more than AVF and were more likely to have heart disease.

She also invoked another recent study by Mu-Yang Hsieh et al that showed an association between blood pressure variability and higher risk of AVF and AVG thrombosis. Although she said intra-dialytic hypotension, pre- and post-hypotension, as well as blood pressure variability, are all “associated” with increased risk of AV access thrombosis, she was careful to note that “association does not establish causation.” She insisted that, though it is “reasonable” to employ treatment of intra-dialytic hypotension and chronic hypotension for patients with recurrent AV thrombosis, such interventions have not been proven to lower the risk of AV access thrombosis.

In patients with heart failure and chronic hypotension, Shaikh described it as preferable to create a radial artery-based AV fistula. If a brachial artery-based AV fistula is created then AV fistula flow rate should be monitored and flow reduction must be considered if the flow rate exceeds 1.5 L/min. In patients who are at high risk of AV fistula failure, an AV graft is a reasonable AV access choice. In patients with poor life expectancy, a CVC can be used as a permanent vascular access.

Shaikh concluded by stressing that, “association between hypotension and AV access thrombosis… does not establish causation,” The final decision on AV access choice should not solely be based on presence of hypotension. Other factors, including “comorbidities, symptoms, frailty status, life expectancy and patient preference” should all be considered.


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