Pediatric nephrologists at Boston's prestigious Children's Hospital recognized that an arteriovenous (AV) access is the preferred vascular access for dialysis delivery in children and adolescents requiring chronic hemodialysis (HD). They also understood that, because of the small size of the accesses, maintenance of an access after it is created becomes all the more important and difficult.
Ultrasound dilution (UD) monitoring of AV access flow is widely used in adult HD units for early stenosis detection, but its experience in pediatrics is limited. Therefore, the Boston group they undertook a study to examine its usefulness in children and adolescents.
The objectives of the study were twofold.
- The first was to evaluate the impact of UD monitoring on AV access-related morbidity, especially access thrombosis. Secondary morbidity outcomes were also evaluated including access-related hospitalizations, and need for new access creation or temporary dialysis catheter placement.
- The secondary objective was to evaluate UD monitoring to screen for hemodynamically significant AV stenosis by:
- Differentiating between patent AV accesses and those at true risk to thrombose.
- Detecting improvements in blood flow to restore patency after interventional procedures.
- To determine UD’s sensitivity and specificity for detecting stenoses vis á vis fistulagrams.
Hemodialysis patients with AV accesses were monitored using UD technology. Its effectiveness was accessed by comparing its results to fistulagrams and its impact on AV-related morbidity.
They found that:
- AV access thrombosis rates fell from 13.5 per 100 patient-months on HD during the baseline period to 3.5 per 100 patient-months on HD during the screening period.
- Secondary complications (hospitalizations, new access creation, temporary dialysis catheter placement) declined from 4 events per 100 patient-months during baseline period and to 2.5 events per 100 patient months during surveillance period.
- Mean blood flow rate by UD measurement was lower in AV accesses that went on to thrombose compared to those that did not thrombose (1,203 ml/min/1.73 m2 vs. 1,683 ml/min/1.73 m2).
- Following angioplasty, median flow rate increased from 730 ml/min to 1,180 ml/min.
- When compared to fistulagrams, UD surveillance was 94% sensitive and 77% specific in detecting hemodynamically significant stenosis, with positive and negative predictive values of 83 and 91% respectively.
The group concluded that noninvasive UD screening is very sensitive in detecting hemodynamically significant stenosis and can decrease AV access thrombosis rates.
