The first hour refill index: a promising marker of volume overload in children and young adults on chronic hemodialysis.

Background: Volume overload is a known risk factor for cardiovascular complications in children on hemodialysis (HD), but a measurable index of volume overload is still lacking.

Methods: We propose a novel index of pre-HD volume overload based on blood volume (BV) monitoring, the first hour refill index (RI), calculated as the ratio between the ultrafiltration rate indexed for body weight during the first HD hour and the percent BV change at the first hour of the treatment. This parameter was retrospectively calculated in 121 sessions in 11 oligoanuric children and young adults on chronic HD, with median age 14.3 years (range 5.4-22.4), and its association with left-ventricular mass index, pre-HD blood pressure, and number of antihypertensive medications was evaluated.

Results: The median RI was 2.07 ml/kg/h/%. There was a significant correlation between RI and median LVMI (r 0.66, p = 0.028), which was 53.4 g/m (45.7-64) in patients with a median RI > 2, and 36.6 g/m (24.9-47) in those with a median RI < 2 ml/kg/h/% (p = 0.01). The number of antihypertensive drugs per patient was significantly higher in patients with a RI > 2 than in those with a RI < 2 ml/kg/h/% (three vs one per patient; p = 0.02) while blood pressure was not significantly different between the two groups.

Conclusions: The ratio between the ultrafiltration rate per body weight and the BV change during the first hour of a HD session could be a promising index of refill capacity and pre-HD volume overload in children and young adults on chronic HD.