Comparison of Hemodialysis Access Flow Measurements Using Flow Dilution and In-Line Dialysance

Measurement of hemodialysis (HD) access flow (Q(A)) is a noninvasive approach for arteriovenous graft or fistula surveillance. Flow dilution (FD) and in-line dialysance (DD) are two common methods for measuring Q(A). In a randomized fashion, we prospectively evaluated Q(A) using FD and DID in 48 HD patients during three separate HD sessions over a span of 3 months. The measurement of Q(A) was similar (1,016 +/- 412 ml/min for FD and 1,009 +/- 425 ml/min for DD, p = 0.44 and 0.79 for the mean and standard deviation, respectively). While FD successfully measured Q(A) >= 2,000 ml/min, DD "saturated" (indicating a Q(A) >= 2,000 ml/min without providing a numerical Q(A) value) (n = 17). The correlation coefficient for Q(A) <= 2,000 ml/min between DD and FD measurements from the same dialysis sessions was high (r = 0.9, p < 0.001) with a straight line slope of 0.997. Access flow values for FD and DID methods were comparable at Q(A) <= 2,000 ml/min and no single method tended to over- or underestimate Q(A) compared with the other. For Q(A)>2,000 ml/min, FD provided a quantitative Q(A) measure, and is therefore a potentially useful tool for Q(A) above this threshold, while DD is not. ASAIO Journal 2009; 55:369-372.