Dialysis arteriovenous access monitoring and surveillance according to the 2017 Spanish Guidelines

Abstract

The Spanish Multidisciplinary Group on Vascular Access (GEMAV), which includes experts from the five scientific societies involved (nephrology (S.E.N.), vascular surgery (SEACV), interventional radiology (SERAM-SERVEI), infectious diseases (SEIMC), and nephrology nursing (SEDEN)), along with the methodological support of the Iberoamerican Cochrane Centre, has developed the Spanish Clinical Guidelines on Vascular Access for Hemodialysis. This article summarizes the main issues from the guideline's chapter entitled "Monitoring and surveillance of arteriovenous access." We will analyze the current evidence on conflicting topics such as the value of the flow-based screening methods for the arteriovenous access surveillance or the role of Doppler ultrasound as the imaging exploration to confirm suspected stenosis. In addition, the concept of significant stenosis and the criteria to perform the elective intervention for stenosis were reviewed. The adoption of these guidelines will hopefully translate into a reduced risk of thrombosis and increased patency rates for both arteriovenous fistulas and grafts.

Screening for hemodialysis graft stenosis and short-term thrombosis risk: A comparison of the available tools

“…In our series, the QaU and QaD < 600 mL/min proposed by the guidelines for access imaging 3–7 showed a very low sensitivity (26%) and excellent or fair PPV (100% for QaU, 75% for QaD) for angiography-proven > 50% stenosis. Their performance differed little from monitoring (its 35% sensitivity being similar to QaU and QaD, and its 68% PPV being similar to QaD, and worse than QaU).…”

“…using the Logiq 7 (General Electric, Milwaukee) with a high-frequency transducer (12–7 MHz) and a mini-convex transducer (5–8 MHz) to assess the outflow veins outside the arm. Gray scale and color imaging of the whole access circuit were done in the longitudinal and transverse planes to check for any StD (>50% lumen reduction and/or stenosis luminal diameter < 2 mm using an electronic caliper and/or downstream spectral Doppler PSV > 400 cm/s) 6,15 and its location (defining as “ inflow stenosis ” any feeding artery, arterial anastomosis, or intragraft stenosis upstream from the venous needle, and as “ outflow stenosis ” any stenosis downstream from the venous needle). QaD was measured in a straight portion of brachial artery in the mid-third of the upper arm at least 5 cm proximal to the anastomosis.…”

“…All guidelines consequently recommend routine graft screening to promptly identify significant stenosis at high short-term risk of thrombosis (>50% lumen narrowing with some functional or hemodynamic impairment) because its elective repair can prevent thrombosis and extend useful access life. 3–7…”

“…A recent meta-analysis of randomized controlled trials (RCTs) showed, however, that surveillance using the early guidelines’ criteria for stenosis repair (Qa < 600 mL/min, presence of StD or VAPR > 0.50) 3–5 is no better in improving outcomes than monitoring (physical examination and/or noting signs of access dysfunction during hemodialysis sessions). 8 All guidelines include monitoring and Qa measurement among the preferred screening methods, sometimes associated with DU, 3,6 or VAPR, 3 but they all agree that evidence of one technique being preferable to another is lacking due to a paucity of adequate comparative studies, none of which—to our knowledge—compared all of the options. 9–12…”

Quantification of the severity of outflow stenosis of hemodialysis fistulas with a pulse- and thrill-based scoring system

“…In our opinion, stenosis with a high risk of thrombosis (high-risk stenosis) is equally as dangerous as stenosis with a high enough shear stress to activate platelets and von Willebrand factor, and could elicit a coagulation cascade. However, it remains unknown how narrow (in millimeters) a high-risk stenosis should be to be labeled “high risk.” Nevertheless, we agree that an area of stenosis with a minimum luminal diameter of < 2 mm should be identified and treated, as recommended by the Spanish Guidelines [ 12 , 13 ], because it plays a role in preventing unexpected AVF thrombosis.…”