BACKGROUND: It is well known hematocrit will increase after hemodialysis, and this phenomenon
is called the hemoconcentration effect. However, the question if a greater ultrafiltration volume will
cause higher hematocrit levels remains controversial. Therefore, further examination of the association
between the ultrafiltration volume and the changes in hematocrit levels during hemodialysis is
needed.
METHODS: A prospective study examining 71 stable hemodialysis patients at the mid-week treatment
(Wednesday or Thursday) and at the first dialysis treatment of the next week (Monday or Tuesday)
was conducted. The association between the ultrafiltration volumes and the changes in hematocrit or
hemoglobin levels at the mid-week treatment and the beginning of the next week treatment was measured.
RESULTS: The results revealed a post-dialysis hemoconcentration effect. However, the ultrafiltration
volume and the changes in intradialytic hematocrit levels revealed no significant correlations
(r = 0.065, P > 0.05 at the mid-week treatment; r = 0.162, P > 0.05 at the beginning of the next week treatment).
CONCLUSION: Our results demonstrated no correlations between the ultrafiltration volume and
the changes in intradialytic hematocrit levels whether at the mid-week treatment or the beginning of the
next week treatment. Many factors such as gender, age, body habitus, and underlying cardiac disease
will determine the intradialytic refilling effect. (Acta Nephrologica 2011; 25: 182-185)
