Influence of Ultrafiltration Volume on Blood Volume Changes During Hemodialysis as Observed in Day-of-the-Week Analysis of Hemodialysis Sessions

Abstract

Monitoring of relative blood volume changes (DeltaRBV) has been propagated for the prevention of hemodialysis hypotension. Although the influence of ultrafiltration volume on DeltaRBV is well-known, there is no mention in the literature that DeltaRBV results should be interpreted differently for the first, second, or third hemodialysis session of the week. To elucidate whether DeltaRBV and its derivative, DeltaRBV normalized for ultrafiltration volume (DeltaRBV/ultrafiltration ratio), vary systematically over the week, we separately analyzed these parameters for the first, second, and third hemodialysis session of the week in 13 chronic hemodialysis patients over a 17-week period. As expected, mean (+/-SD) ultrafiltration volume was significantly (p < 0.001) higher during the first session than during the second and third hemodialysis sessions (3163 +/- 615, 2622 +/- 674 and 2607 +/- 638 ml, respectively). DeltaRBV was significantly (p < 0.01) more negative at the first session than at the second and third hemodialysis sessions (-10.1 +/- 2.7, -9.3 +/- 3.0 and -9.3 +/- 3.1%, respectively). The DeltaRBV/ultrafiltration ratio was significantly (p < 0.01) less negative at the first session than at the second and third hemodialysis sessions (-3.2 +/- 0.6, -3.5 +/- 0.8 and -3.6 +/- 0.6%/l, respectively). In conclusion, DeltaRBV and the DeltaRBV/ultrafiltration ratio differ systematically between the first and other hemodialysis sessions in patients on a thrice-weekly hemodialysis schedule, most likely as a result of different ultrafiltration volumes.

Determinants and Short-Term Reproducibility of Relative Plasma Volume Slopes during Hemodialysis

“…This finding is consistent with previous studies (17,18). UFR acts as a stress stimulus and evokes a change in RPV slope.…”

“…Given these considerations, it seems that RPV slopes can serve as a tool to assess volume status. The use of RPV slope and its derivatives (RPV/UFR or RPV/UFR adjusted for body weight) has been proposed as a tool to assess volume status and hence, adjust dry weight (17,21,(24)(25)(26)(27)(28). These studies propose that a flatter RPV slope can tolerate a greater dry-weight reduction (19,21,27,28).…”

“…Thus, the interpretation of RPV slope requires knowledge of UFR. Although the RPV/UFR ratio has been proposed as a surrogate marker for volume assessment (17,21,(24)(25)(26)(27)(28), it is, in our view, better to view each component of the equation separately because of the clinical information that each part provides.…”

“…In a randomized trial, it was found that probing dry weight leads to steepened RPV slopes (21). Data on intraindividual (17,18) and interindividual variability (18,20) of relative blood volume monitoring are limited.…”

“…RPV slopes associate with all-cause mortality, even after accounting for interdialytic ambulatory BP and interdialytic weight gain (4). However, reproducibility of RPV within individuals remains unknown (15)(16)(17)(18)(19)(20)(21). Gauging reproducibility is important, and therefore, the reliability of this test can be ascertained.…”