Determining when to measure vascular access flow …that may not be enough
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To the Editor,
Vascular access in hemodialysis patients is crucial. Vascular access monitoring to ensure access patency is important for patient survival, quality of life, and blood vessel care. The ultrasound dilution method for measuring access flow is a screening tool to assess access dysfunction. Park et al. [1] performed a single-center prospective study of the variation in access flow during hemodialysis, and we have some questions and comments.
The study showed the effects of intradialytic change in blood pressure and ultrafiltration volume on the variation in access flow. As the authors mentioned, access flow measurement is useful for vascular access surveillance. However, what can we predict based on the variable flows? We doubt whether the flow variation could help to predict vascular access events. If patient data for vascular access events (thrombosis or stenosis) were available, the authors would have more informative results.
According to the study reported by Park et al [1], the mean vintage of access was almost 5 years with a wide range of distribution. Because the duration of dialysis may influence the vascular patency and blood flow, previous studies enrolled only the incident hemodialysis patients [2], [3]. The sample size in the study by Park et al [1] was too small to adjust for the duration of dialysis.
Finally, the heterogeneity of vascular access should have been considered in the data interpretation. Because arteriovenous grafts and native fistulae have completely different physiologies, different cutoff values for vascular patency have been recommended according to the vascular access type [3].