Standards for reproducible access flow measurements

Practical techniques for determining the access flow rate during hemodialysis are reviewed and compared; all are based on indicator dilution principles. The precision of duplicate determinations of the access flow rate in close succession during a given treatment session for all techniques is good; the coefficients of variation vary from 5 to 12%. Access flow measurements during an entire treatment session or from one treatment to another may be considerably more variable since changes in systemic hemodynamics can alter the access flow rate. The influence of variability in access flow measurements on tests for access surveillance is illustrated by data simulations using the Monte Carlo method. Improved approaches for normalizing access flow measurements to changing hemodynamic conditions are desirable to permit more accurate predictions of access stenosis and thrombosis.