Measuring the adequacy of hemodialysis access

Vascular access morbidity is still an important problem. The risk of thrombosis increases in prosthetic grafts as the access flow decreases below 600 ml/min, whereas native arteriovenous accesses can maintain patency at much lower flows, in some cases flows below those needed to deliver adequate dialysis. Intra-access pressures are also dissipated differently in the two access types. These differences between native and prosthetic grafts determine the utility of the monitoring techniques that are useful for detecting stenosis and assessing function in the two access types. Modern non-urea methods for measuring access recirculation are therefore useful in native but not in graft hemoaccesses. Direct or indirect intra-access pressure measurements and direct flow measurements are most useful in grafts to detect and then correct lesion before thrombosis.