We sought to determine if modified ultrafiltration (MUF) in the current era was associated with improved outcomes after neonatal cardiopulmonary bypass (CPB).

Retrospective analysis of the PC⁴/NEPHRON dataset from 22 centers (2015-18). Neonates were stratified by MUF use and outcomes were compared. Multivariable regression models were adjusted for center use of MUF and high-risk covariates.

There were 1,654 neonatal CPB operations, 993 (60%) utilized MUF. MUF was not evenly distributed among centers. Patient characteristics were similar between cohorts with notable exceptions: the MUF cohort had fewer Hispanic neonates, more STAT 5 operations, shorter CPB times, more frequent use of deep hypothermic circulatory arrest and fewer STS preoperative risk factors. The MUF cohort had less fluid accumulation, including in the operating room and at peak postoperative fluid balance. Mortality, duration of invasive ventilation, length of stay and clinically important bleeding were not different between MUF and non-MUF neonates. In multivariable analysis, neonates receiving MUF had a higher likelihood of achieving a first daily negative fluid balance prior to postoperative day 3 (OR 1.98, 95% CI = 1.38-2.84).

MUF use was associated with lower early postoperative fluid accumulation. MUF did not result in a significantly shorter duration of invasive ventilation, a shorter length of stay, or lower mortality.