Do changes in relative blood volume monitoring correlate to hemodialysis-associated hypotension?

Intradialytic hypotension remains the most common complication for outpatient hemodialysis, and relative blood volume monitoring was designed to reduce hypotension. Reports of the usefulness of this technology, however, have been variable.

We audited the usefulness of relative blood volume monitoring recorded throughout the mid-week dialysis in 72 stable adult outpatients who had multifrequency bioimpedance measurements.

The blood volume measurement (BVM) at the end of the session was 91.6 ± 0.6% and was not different from the nadir BVM recorded (90.7 ± 0.5). The BVM was strongly correlated with change in hematocrit (r = -0.56, p < 0.001) and albumin (r = -0.69, p < 0.001), but had no relationship with pre-, intra- or postdialysis blood pressure recordings. The BVM was not associated with ultrafiltration volume, but did correlate with a postdialysis change in extracellular fluid volume (r = -0.39, p = 0.006).

In this audit, although the BVM at the end of the dialysis session was correlated with changes in hematocrit, serum albumin and extracellular fluid volume, the change in the relative BVM did not mirror changes in intradialytic blood pressure.